TRX250R.ORG
Workshop => Carburetor, Intake, and Exhaust => Topic started by: Pumashine on November 15, 2014, 03:20:50 PM
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Started running the 40mm billet smart carb back in February 2014. The loaner carb had float bowl issues. After resetting the float heights it was not refilling the bowl quick enough. It would like just die at full throttle. Low and behold the tech at APT says it is very touchy setting the float height while still maintaining refill flow rate. The carb was real lean compared to a normal carb on the bottom end. Seemed to breath fresh air into riding in first and second gear. This prompted me into getting a 40mm billet for myself. Put her on and got her started. Seemed to be just a tad to lean so I proceeded to richen the clicker every couple hours fearing I was going to seize her up at WOT. From 1/2 to full throttle there was a stumbling spot. I contacted APT and requested a richer Fuel Metering Rod or FMR.
Received a new 76 FMR a couple weeks later and put it in to replace the leaner 78 FMR. I did not write down how many clicks I had the clicker set at. I was instructed to get the bike started going about 50 to 60 clicks from full rich. Then keep going leaner until the idle started to get angry. Like when your bike is running out of gas. It will rev up for awhile and then come back down a little and repeat. Once the idle gets a little angry you then set it 2-3 clicks richer until you have a perfect idle. Once you get a perfect idle you can then drop the idle speed down to where you like it at.
I was really excited now the FMR was richer and I hope to get the stumbling out of the 1/2 throttle area. Went out for the usual dune ride at Winchester bay. Was great 0 to 1/2 throttle. Was stumbling still at 1/2 throttle. When full throttle was achieved she ran great. I was still not sure what was causing her to stumble. Rode the rest of the day and figured I would ask questions on Monday. Kyle Burns put it this way summarizing where the clicker works.
My understanding is this is alot like a Lecton. But there is no jet. You slide the FMR up or down to control idle to 1/2 throttle. 1/2 to full throttle I determined by the FMR itself.
So I went 3 clicks richer the next weekend. I get to the dunes and go to start her up and she just won't start. I notice gas dripping out of the header pipe. Had someone pull start me. Had to get pulled around the parking lot but would not start until I let off the throttle completely and just barely fired. It gets going and I go for another dune ride. After coming back and having a beer and refueling I go to start up again. Won't start. So I do the pull start thing again. Same results, like it was flooded. Went for another ride and same scenario. Was making chirping noises under full throttle. Like metal on metal as the train goes by. Would not start again after cooling down in the parking lot. Seemed strange if you stopped out on the dunes for a minute she would start right back up when hot. Loaded her back up and went home.
The next week I took the seat off and double checked the boot was sealing around the intake manifold. It seemed a little loose when I checked it out riding the weekend before and tightened the clamp. My thoughts were maybe it was loose and moved on me. After loosening and trying to move the carb forward I tightened it back up and turned 3 clicks richer, it actually started. Thought maybe it would not start due to extreme lean condition as stated in the manual.
Tried again the next weekend. Again the bike won't start so I got a pull start. Each time coming back for more fuel I just let her idle instead of hitting the kill switch. Just turned the idle up a bit. I had noticed after setting my idle at home I had to turn it up after getting to the dunes the last couple weekends. I went and gave her 3 clicks richer and was going to go do a plug check. As I got to 1/2 throttle just to about 3/4 open the piston froze up. SOB, did I go 3 clicks the wrong way? I got off the bike and started pushing her back to the parking lot. A guy rides up and asks me if I am out of gas. I look at him and say "I Wish" As I was sitting there waiting I kicked and the piston broke loose. Zero compression.
I'm like :wtf?:
APT says if the carb is hitting the frame it vibrates the carb not allowing it to atomize the fuel correctly. This week Kyle or Ryan was saying this creates a lean condition. So I went and took pics to show no frame touching.
(http://i62.tinypic.com/fz3t42.jpg)
(http://i58.tinypic.com/54dicg.jpg)
Measuring from the carb to the intake is 3/4" in this pic
I then removed the boot and set it back to 3/4"
(http://i57.tinypic.com/i36k9u.jpg)
Now you can see the carb is touching the intake on the far side. This indicates to me that the carb touching the motor may do the same thing as the carb touching the frame. Even though no one mentioned this as a possibility. Heres a better pic so you can see how hard it is touching. The black sharpie line is where the boot was on the intake. It was up tight against the carb.
(http://i57.tinypic.com/othmd2.jpg)
The plug is tan at piston freeze. I took this pic as I was taking the cylinder off.
(http://i60.tinypic.com/33cm6wz.jpg)
So the whole time starting February until now (November) the carb has been experiencing the lean condition intermittently? (every 5 minutes) I am guessing. Seems the aluminum has been eaten away on the exhaust side of the piston.
(http://i59.tinypic.com/qx10t4.jpg)
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Make sure you do a plug chop with the smart carb. Burns had to make the change to the metering rod. Mine just fried the piston. You don't want to be too lean breaking in the 363
What type of riding were you doing the last 15 seconds or so before the piston failure? Show us the top and all sides of the piston.
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What type of riding were you doing the last 15 seconds or so before the piston failure? Show us the top and all sides of the piston.
Straight line from the parking lot to the flats for a plug chop. What does it look like happened or is happening?
(http://i61.tinypic.com/24wycfc.jpg)
(http://i60.tinypic.com/1235nyh.jpg)
(http://i57.tinypic.com/20tqmwp.jpg)
(http://i60.tinypic.com/2z68fo0.jpg)
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Take it or leave it but this comes from someone that knows a little about vibration owning a cr500 in a quad chassis haha. try running a drop or 2 of silicone per gallon in your gas/oil mix
The oil industry uses silicone to stop foaming so this is not just some crazy idea you read on the internet. still not convinced? take a clear pickle jar and put your oil/gas mix in it and shake it very hard, then add some silicone from armor all or a tire dressing that uses silicone. now shake it just like you did the first time, in my testing i had less bubbles with silicone than without.
yeah yeah you will have someone tell you the silicone is going to foul your plugs blah blah blah, listen to someone that runs it in every tank full if you want to help with foaming.
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Take it or leave it but this comes from someone that knows a little about vibration owning a cr500 in a quad chassis haha. try running a drop or 2 of silicone per gallon in your gas/oil mix
The oil industry uses silicone to stop foaming so this is not just some crazy idea you read on the internet. listen to someone that runs it in every tank full if you want to help with foaming.
I did not know there was a term for it. I was gonna take a pie shape piece out of the cr500 intake manifold so the carb was not touching. Will this help to stop foaming or is it the nature of the beast?
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The piston shows severe detonation. An engine that experiencing that much detonation was announcing very loudly that it was experiencing detonation and it was going to make you walk home if you do not do something to stop the detonation. If you do not know what detonation sounds like, try to remember the noise the engine made especially the last 15 seconds or so of its life. Detonation usually sounds like large rocks hitting the engine cases or skid plate. I have never heard detonation create a chirping noise. Many times an engine will emit a chirping noise from the muffler when the ignition timing is severely retarded or the air fuel ratio is so lean it is causing a lean miss-fire.
When the onset of detonation begins or has lite detonation, it may make the knocking noise every second or so and will increase it's frequency to occurring almost every engine revolution if the conditions causing the detonation is not eliminated. Most detonation on a problematic engine is predictable in the sense it can be initiated by letting the engine reach a particular engine temp. a particular RPM and or throttle position to re-create the detonation so the source can be determined.
If the engine experiences detonation at the same RPM regardless of the throttle position it may be a foaming the fuel due to vibration like Dave mentioned. If the engine experiences detonation at a particular RPM and throttle position it is probably carburetor mixture related. On conventional carburetors the correct circuit can be enriched or leaned once you know the throttle position the problem occurs. I do not know how many different needles Smart Carb makes and if their needles can change the mixture in one throttle position without affecting the mixture on either side of that particular throttle position. When I worked with the Edmonds on the Lectron in the Late 1970s we could not make these throttle position specific adjustments to get precise fuel metering at one throttle position without affecting it on either side of that throttle position even with all of the custom needs they made for our works bikes.
The carburetor touching the engine or chassis will often cause the fuel in the float bowl to turn to foam at a particular RPM and the mixture will go very lean when this condition exists. I also noticed you have a Boysen Rad Valve. I have had a lot of problems on the Dyno with the fuel foaming on engines that have the Rad Valve. Most of the time it foams the fuel over a very narrow RPM range and does not cause a problem in the real world unless you stay in problematic RPM range for more than a second or two. The Rad Valves typically flow air real well and make good power but their design eliminated the necessary vibration isolation that the stock rubber manifolds provide. Many old rubber manifolds when they get hardened will also cause carburetor vibration issues.
There are two different types of foaming of liquids that I am aware of. One type, the foam builds on the surface and liquid is still under the layer of foam. The other type is when the fuel in the float bowl is foam from the top to the bottom of the float bowl and is usually caused from cavitation. I am not sure if changing the surface tension of the liquid by adding silicone will prevent foaming due to cavitation.
My experience with foaming due to cavitation on the dyno, causes the floats to sink to the bottom of the float bowl and opens float valve and causes fuel to run out of the vent lines while the engine goes severely lean because the main jet is sucking foam. It is not possible to observe if this phenomena is occurring with the Smart Carb because of its lack of vent lines.
I will continue with the evaluation when I have more time.
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Tony have you tried the rubber UPP cr500 boot? If you don't like Vforce reed try a stock cr500'cage with the UPP boot
calvin told me the a Kart guy with a liger running the short mikuni 2 bolt rubber intake was losing 2 horsepower from vibrations transferring to the carb. I believe he fiquired that out by holding the carb with his hand To dampen the vibes. I believe calvin was working with UPP to build them a straight boot like the caracal but less downward angle I believe.
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Tony have you tried the rubber UPP cr500 boot?
I am a rad valve guy from the beginning. I am not opposed to the other systems but have never had a need to. I am switching to V-force on the mini-tooth. This is all new to me and have not considered anything other than dealing with the current problem. I am thankful for all the advice. We are building an intake for the mini-tooth as the UPP boot is way extremely to large for the 40mm. For now I was just going to alter the carb to intake contact and use the armor all as you suggested.
(http://i57.tinypic.com/10gcwpe.jpg)
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if you were using a unmodified boyesen intake boot, theres no way the carb can touch the reed block because theres rubber spacer inside the boot that wont allow it to happen
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if you were using a unmodified boyesen intake boot, theres no way the carb can touch the reed block because theres rubber spacer inside the boot that wont allow it to happen
Even with a an unmodified Boysen rubber connector, there are sometimes problems with the vibrations reaching the carburetor. I believe that the 5mm or so of rubber spacer used between the reed and carb on the majority of the Boysen boots are too short and not flexible enough to keep the vibrations of the engine from getting to the carb. Oem rubber manifolds often have over an inch of rubber between the carb and reed to help damp the vibrations.
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Tony here is a couple options for the mini tooth, the first one uses a cr500 manifold, the second is a cr250 manifold using the plates you made for me.
The first picture using the cr500 manifold does not show your plate but it was setup to use it also for a better seal to the reed cage.
this setup is using the arctic cat m1000 reed cage along with a removable reed stuffer only found in the 500's. Everything gets port matched from the carb outlet to the stuffer.
(http://i870.photobucket.com/albums/ab265/rsss396/ba68e2ed949276f83653703e95005a78_zps6d23b370.jpg)
Cr500 cleaned up to look good
(http://i870.photobucket.com/albums/ab265/rsss396/814faebe59f3e842abda693b91719fa0_zpsc7f22914.jpg)
Cr250 manifold
(http://i870.photobucket.com/albums/ab265/rsss396/85f3b3e9a56df4ad8fd29631959f3344_zps8f1942b5.jpg)
(http://i870.photobucket.com/albums/ab265/rsss396/167637a155e853cd331257001a02553f_zps543f2d28.jpg)
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I believe that the 5mm or so of rubber spacer used between the reed and carb on the majority of the Boysen boots are too short and not flexible enough to keep the vibrations of the engine from getting to the carb. Oem rubber manifolds often have over an inch of rubber between the carb and reed to help damp the vibrations.
OK I get. Thank you Jerry for your insights. Even if there is a gap it really needs to be an inch or so long or foaming will occur. Thanks Dave for the pics. I will have to do some homework and find out which Cr 500 intake will work with the 40mm SC. I recall having a heck of a time fitting the 39mm carb into the stock pilot boot.
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The cr500 only uses a 38 carb so any of them will work, the later years are the only ones available
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both those intake were setup for a 44 lectron carb ( with the outlet turned down some )
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Even with a an unmodified Boysen rubber connector, there are sometimes problems with the vibrations reaching the carburetor. I believe that the 5mm or so of rubber spacer used between the reed and carb on the majority of the Boysen boots are too short and not flexible enough to keep the vibrations of the engine from getting to the carb. Oem rubber manifolds often have over an inch of rubber between the carb and reed to help damp the vibrations.
definatly the oem inlet boot isolates the carb in more rubber than the boyesen boot. but why is the smartcarb not doing well with vibration, if indeed vibration is the culprit to the seizure ? ive used radvalves in the past with keihins and dont ever recall any tuning problems from vibration transfering from the engine to carb
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heres my take on it. if your not concearned with gas mileage or ride from sealevel to 10,000' in the same day (which is a couple benefits the carb is 'supposed' to have ), i would throw that smartcarb in the bush and use a keihin, or even a mikuni. if gas mileage is a concearn, seems like maybe this sport isnt for you. youve already got a ton of money invested in the bike, whats a extra $5 in gas each time you ride.
i get the feeling your chasing some benefits that may not even exist. the people at smartcarb made alot of claims, other than seat of the pants testimonials from average customers ( which are anything but scientific or concrete), im not sure any of the claims have been legitimatly substantiated. i know theres people still having problems with the smartcarb. some have even thrown in the towel and sold it or got a refund
cant recall his name but the other guy on this site using the smart carb made a video, honestly it didnt sound like his was running all that well either
ive seen other vids were guys are jumping for joy at how well the carb seems to work, but yet the vid says otherwise. one guy installed one on a snowbike and raved how good it worked, yet the rpm was hanging like mad everytime he let off the throttle. this tells me the guy has blinders on and is just another victim of the hype
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heres my take on it. if your not concearned with gas mileage or ride from sealevel to 10,000' in the same day (which is a couple benefits the carb is 'supposed' to have ), i would throw that smartcarb in the bush and use a keihin, or even a mikuni. if gas mileage is a concearn, seems like maybe this sport isnt for you. youve already got a ton of money invested in the bike, whats a extra $5 in gas each time you ride.
i get the feeling your chasing some benefits that may not even exist. the people at smartcarb made alot of claims, other than seat of the pants testimonials from average customers ( which are anything but scientific or concrete), im not sure any of the claims have been legitimatly substantiated. i know theres people still having problems with the smartcarb. some have even thrown in the towel and sold it or got a refund
cant recall his name but the other guy on this site using the smart carb made a video, honestly it didnt sound like his was running all that well either
ive seen other vids were guys are jumping for joy at how well the carb seems to work, but yet the vid says otherwise. one guy installed one on a snowbike and raved how good it worked, yet the rpm was hanging like mad everytime he let off the throttle. this tells me the guy has blinders on and is just another victim of the hype
Every carb that I have tried to tune that was designed by the Edmonds since the Lake Injector (Lectron) has just been a Lectron with different lip stick. Time will tell if the Smart Carb is also a Lectron with different lip stick and has the same limited tuning capabilities as it's 3 ancestors.
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well if a guy insists on using one of these jetless carbs, it seems like the lectron might be the better choice at this stage in the game. a year from now the smartcarb might be superior but it sure doesnt seem like the way to go as of now
some of these guys that buy the smart carb really piss me off. they say how good it works but in the same sentence they say its either to lean and down on power or its spooging oil all over. either it works good or it dont. simple as that. like i said before, i think most of these goons that buy the smartcarb have blinders and refuse to recognise the problems for what they are. like this moron that just wrote this today on another site. clearly hes having issues but goes on to say even with all the trouble its still better than a keihin ???????? what the hells wrong with these people . no offense to anyone here as im mostly refering to all the other people from different sites. far as i know i havent seen anyone around here mention their smartcarb troubles and in the same breath also proclaim how much better it is than keihin
Hey Corey you make that tuning video yet?
I like my smartcarb but honestly I can't figure out how to set the needle perfectly. It just doesn't give me the feedback I'm used to getting from a stock carb. When I lean it out a bunch it is down on power, when I richen it a bunch I start getting spooge but I can't seem to find the middle. Always have to blip it a little to keep it running at idle.
The bike definitely rips with the smartcarb and it's a big improvement over the keihin but I'd like to get it running perfect
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(http://i59.tinypic.com/qx10t4.jpg)
The picture of the top of the piston is a perfect example of what detonation will do to the top of the piston.
Notice the etching or sand blasted band that starts next to the bore. The band is about 3 mm to 5 mm wide and starts at about 8 o'clock and stops at about the 4 o'clock position. The destructive forces of detonation have actually removed metal from the top of the piston in this band that looks sand blasted.
If you look closely at the head, you will also see the same band of destruction in the outer edges of the head.
A close inspection of the o-ring that is next to the bore and the inside of the o-ring (closest to the bore) will usually show etching and or erosion of the rubber. Mild detonation over a longer period of time will gradually erode the inner o-ring to the point it can no longer seal. Severe detonation over a period of 15 seconds or less will create the piston we are looking at, lead to severe piston overheating and result in a seized piston with possibly mild 0-ring erosion along it's inner circumference. Increasing the distance from the bore to the o-ring grove will help protect the 0-rings from detonation. If I had the option of redesigning the cylinder, I would move the studs and o-ring groves at least another 3 to 4 mm further from the bore.
The destructive forces from detonation will eat away the top edges of the piston, the edge of the cylinder where the bore and head gasket surface intersect, the outer edges of the squish band as well as the o-ring and head gasket if it has one. Detonation is also hard on connecting rod bearings, main bearings, bearing pockets and causes the engine cases to crack through the middle of the bearing pockets.
The piston crown has experienced intense heat. The heat has been so intense that it has consumed all of the carbon from the crown of the piston. The exhaust temperature has also been excessively high, indicated by the edged of the piston being burned away next to the exhaust port. Wiseco piston crowns that experience this level of temperature will usually “sag” or “droop” between the center of the piston and the exhaust side of the piston. If you look at the underside of the piston you will probably see dark ash deposits. Look at and feel the top of the piston to see if the crown has a spot that has sagged.
In the next discussion we will talk more about what causes detonation and what can be done to eliminate it.
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so the million dollar question. can a foaming carb cause all this destruction or is there several things at fault here. i have hard time believing a foamed float bowl caused all this by itself. we know nothing about the engine setup. comp ratio, timing, pipe, head geometry, fuel, oil. we know nothing. so it seems impossible to make a conclusion what happened
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For sure foaming can do this. If you run it on a dyno with fuel flow reading, you will see fuel flow go erratic then no flow under WOT. When you see fuel flow bounce, kill the motor, check to see if its grounding out (just as he did). If it looks good, move the carb back / add intake boot. Retest, if still a issue add weight to the bell mouth (epoxy wheel weights to clamp or bowl). Sometimes it's not just foam, the vibration will act as a Hz frequency on the needle and seat, like a impact on a nut. Then your into fluid dampers and moving rpm around
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My cr500 based drag bike has vibrated bad enough to lift Lectrons adjustable slide needle and turn it, which then leans the motor out because the flat side of the needle no longer faces the motor.
For those that do not know, if the flat side does not face the motor less fuel is pulled from the carb bowl. The flat side on the needle creates a low pressure area when air rushes by thus pulling more fuel than your typical round style needle found on a kiehin or mikuni
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so the million dollar question. can a foaming carb cause all this destruction or is there several things at fault here. i have hard time believing a foamed float bowl caused all this by itself. we know nothing about the engine setup. comp ratio, timing, pipe, head geometry, fuel, oil. we know nothing. so it seems impossible to make a conclusion what happened
ll
Testing, testing, testing, testing and using the process of elimination can only answer this question. A fully instrumented bike with data loggers while testing riding in the real world, is the only way I have been able to solve these types of problems when doing consulting for engine manufactures.
Sometimes all that needs to be done is change the riding style (the throttle position and RPM) to that for which the engine was designed. Two stroke engines that have been developed to medium to high levels of power output should not be used for just cruising around because of detonation related issues due to poor scavenging. This is the main reason manufactures pulled the plug on large two stroke street bikes. It was not because of emissions like most of the world believes.
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if the pipe was changed it could make the problem better or maybe worse, allot of dynamics going on, but IMO I would add a simple power jet to this motor but thats just me.
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Looks like Lectron runs power jets on their carbs.
http://www.lectronfuelsystems.com/carburetor/
(http://forums.trx250r.org/vbulletin_imports/133_3677_2017-04-18_6816.jpg)
I wonder if one could be adapted to the smart carb?
This is from their FAQ:
"Should I have a power jet carburetor or not?
This is a must for a two stroke engine. We prefer to have them on all types of engines two or four stroke.
The power jet carburetor can give you a wider range on tuning and also helps you fine tune top end power on all types of engines."
"What does the power jet do for tuning?
The power jet is for high speed tuning only. The power will kick in about 3/4 from top RPM First get the motor running good at idle and mid-range then work on the power jet.
The power jet will not effect the tuning of idle, mid-range, or response on the carburetor."
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The smart carb essentially already has a power jet. The pressurized fuel bowl does the same thing. There is a tunnel that connects the air side of the carb bell to the fuel bowl. When at wot when the signal from the engine is at its strongest, the tunnel creates a huge pressure that draws even more fuel into the air stream, just like a power jet does. People keep comparing these to Lectrons but their only similarity is that they are both single circuit flat side carbs. The similarity stops there. How they operate are very different. Corey will speak more about this shortly.
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Started running the 40mm billet smart carb back in February 2014. The loaner carb had float bowl issues. After resetting the float heights it was not refilling the bowl quick enough. It would like just die at full throttle. Low and behold the tech at APT says it is very touchy setting the float height while still maintaining refill flow rate. The carb was real lean compared to a normal carb on the bottom end. Seemed to breath fresh air into riding in first and second gear. This prompted me into getting a 40mm billet for myself. Put her on and got her started. Seemed to be just a tad to lean so I proceeded to richen the clicker every couple hours fearing I was going to seize her up at WOT. From 1/2 to full throttle there was a stumbling spot. I contacted APT and requested a richer Fuel Metering Rod or FMR.
Received a new 76 FMR a couple weeks later and put it in to replace the leaner 78 FMR. I did not write down how many clicks I had the clicker set at. I was instructed to get the bike started going about 50 to 60 clicks from full rich. Then keep going leaner until the idle started to get angry. Like when your bike is running out of gas. It will rev up for awhile and then come back down a little and repeat. Once the idle gets a little angry you then set it 2-3 clicks richer until you have a perfect idle. Once you get a perfect idle you can then drop the idle speed down to where you like it at.
I was really excited now the FMR was richer and I hope to get the stumbling out of the 1/2 throttle area. Went out for the usual dune ride at Winchester bay. Was great 0 to 1/2 throttle. Was stumbling still at 1/2 throttle. When full throttle was achieved she ran great. I was still not sure what was causing her to stumble. Rode the rest of the day and figured I would ask questions on Monday. Kyle Burns put it this way summarizing where the clicker works.
So I went 3 clicks richer the next weekend. I get to the dunes and go to start her up and she just won't start. I notice gas dripping out of the header pipe. Had someone pull start me. Had to get pulled around the parking lot but would not start until I let off the throttle completely and just barely fired. It gets going and I go for another dune ride. After coming back and having a beer and refueling I go to start up again. Won't start. So I do the pull start thing again. Same results, like it was flooded. Went for another ride and same scenario. Was making chirping noises under full throttle. Like metal on metal as the train goes by. Would not start again after cooling down in the parking lot. Seemed strange if you stopped out on the dunes for a minute she would start right back up when hot. Loaded her back up and went home.
The next week I took the seat off and double checked the boot was sealing around the intake manifold. It seemed a little loose when I checked it out riding the weekend before and tightened the clamp. My thoughts were maybe it was loose and moved on me. After loosening and trying to move the carb forward I tightened it back up and turned 3 clicks richer, it actually started. Thought maybe it would not start due to extreme lean condition as stated in the manual.
Tried again the next weekend. Again the bike won't start so I got a pull start. Each time coming back for more fuel I just let her idle instead of hitting the kill switch. Just turned the idle up a bit. I had noticed after setting my idle at home I had to turn it up after getting to the dunes the last couple weekends. I went and gave her 3 clicks richer and was going to go do a plug check. As I got to 1/2 throttle just to about 3/4 open the piston froze up. SOB, did I go 3 clicks the wrong way? I got off the bike and started pushing her back to the parking lot. A guy rides up and asks me if I am out of gas. I look at him and say "I Wish" As I was sitting there waiting I kicked and the piston broke loose. Zero compression.
I'm like :wtf?:
APT says if the carb is hitting the frame it vibrates the carb not allowing it to atomize the fuel correctly. This week Kyle or Ryan was saying this creates a lean condition. So I went and took pics to show no frame touching.
(http://i62.tinypic.com/fz3t42.jpg)
(http://i58.tinypic.com/54dicg.jpg)
Measuring from the carb to the intake is 3/4" in this pic
I then removed the boot and set it back to 3/4"
(http://i57.tinypic.com/i36k9u.jpg)
Now you can see the carb is touching the intake on the far side. This indicates to me that the carb touching the motor may do the same thing as the carb touching the frame. Even though no one mentioned this as a possibility. Heres a better pic so you can see how hard it is touching. The black sharpie line is where the boot was on the intake. It was up tight against the carb.
(http://i57.tinypic.com/othmd2.jpg)
The plug is tan at piston freeze. I took this pic as I was taking the cylinder off.
(http://i60.tinypic.com/33cm6wz.jpg)
So the whole time starting February until now (November) the carb has been experiencing the lean condition intermittently? (every 5 minutes) I am guessing. Seems the aluminum has been eaten away on the exhaust side of the piston.
(http://i59.tinypic.com/qx10t4.jpg)
From looking at your pictures it appears that mixture values were fairly close to optimum as indicated by the plug. If this is indeed the plug as you removed it from the seized engine, (I'm not implying that I don't believe you) the mixtures certainly weren't lean enough to cause the localized overheating of your piston and ultimate seizure that occurred. I believe the evidence would indicate that the front spigot of the carburetor was hard touching the intake manifold enough to cause severe shaking of the carb and aeration of the fuel in the bowl enough to lean it down to critical conditions in the mid to top end. I would also be inclinded to say that this was likely the trouble all along and the richer metering rod is probably not necessary. Furthermore this was also the cause of the intermittent flooding issues that you were dealing with prior to the seizure. After your rebuild and necessary clearancing of the manifold I would also inspect your SC to see if any damage has occured the the fuel inlet needle/seat.
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well if a guy insists on using one of these jetless carbs, it seems like the lectron might be the better choice at this stage in the game. a year from now the smartcarb might be superior but it sure doesnt seem like the way to go as of now
some of these guys that buy the smart carb really piss me off. they say how good it works but in the same sentence they say its either to lean and down on power or its spooging oil all over. either it works good or it dont. simple as that. like i said before, i think most of these goons that buy the smartcarb have blinders and refuse to recognise the problems for what they are. like this moron that just wrote this today on another site. clearly hes having issues but goes on to say even with all the trouble its still better than a keihin ???????? what the hells wrong with these people . no offense to anyone here as im mostly refering to all the other people from different sites. far as i know i havent seen anyone around here mention their smartcarb troubles and in the same breath also proclaim how much better it is than keihin
Hey Corey you make that tuning video yet?
I like my smartcarb but honestly I can't figure out how to set the needle perfectly. It just doesn't give me the feedback I'm used to getting from a stock carb. When I lean it out a bunch it is down on power, when I richen it a bunch I start getting spooge but I can't seem to find the middle. Always have to blip it a little to keep it running at idle.
The bike definitely rips with the smartcarb and it's a big improvement over the keihin but I'd like to get it running perfect
Forums were made for the squeaky wheel. Most likely people will not post until they are having an issue or out of fairness post to make people aware of the issues they are having hoping to find a fix. Interesting indeed that even with a nagging issue they haven't yet figured out they are still willing to admit it's better than what they had. What you don't hear on the forums is the 95%+ success that we actually have in the field with all carburetors sold or the people that later found out it was an issue with their bike and that they had simply been tuning around a problem for years with their multiple circuit Keihin. The third party validations, testimonies of dramatic increases in fuel economy and flawless bottom to top performance, dyno video's from DirtRider magazine, articles in Endurocult and quite a few european magazines that aren't necessarily read in the states, on road US and european emissions certifications without the use of precious metal catalysts. It's all out there and the realities of this fuel system will become more evident with time. It's funny you mention videos though, I've made a living out of tuning two strokes and designing two stroke engine products and I listen to these videos and can't tell anything about how the engine is actually running based on crappy phone camera microphone. At least not to the point of calling a person a moron, perhaps you have a better ear than I.
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Furthermore this was also the cause of the intermittent flooding issues that you were dealing with prior to the seizure.
Thankyou for confirming the theory my problem was the engine vibration. The cause of flooding and not starting is caused by what? I just do not understand what you are saying. Are you saying the 76 FMR is too rich? Please don't mind the members on this forum. Some like to say I told you so. I agree your carb is amazing. I just believe the vibration has caused the intermittent lean condition and in time the piston ultimately failed. I have ordered a rubber intake manifold to get away from the intake manifold hitting the carb.
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All that shaking will also upset the fuel inlet needle and seat. In your case I believe it caused the needle/seat to begin leaking intermittantly leading to flooding and hard starting.
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nice to see you joined up :redbull:
ill bet its a difficult business to be in. surely your aware that alot, maybe most, of your carbs are going to customers with near zero mechanical ability, or so it seems. this leaves the door open for a ton of backlash from customers that cant tune a simple lawnmower let alone a high performance 2stroke. i certainly dont have the patience you do to deal with that stuff. so my hats off to you for having nerves of titanium :congratulatory:
perhaps the squeeky wheel stories stand out in my mind more than the sucess stories for some reason. like you say though, maybe very few of the good experiences get told on the forums . but when i think of smart carb i just remember the not so good experiences ive heard about. like the guy whos tipover balls ( i think that was the problem if i recall) got stuck and floaded his crank case, and i believe blew his reeds out. then some how the engine caught fire. not to find humor in someone elses misfortune but the story was kinda funny
maybe someday ill get the chance to ride a bike with a welll tuned smartcarb and i can get a first hand glimpse what its all about
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Started running the 40mm billet smart carb back in February 2014. The loaner carb had float bowl issues. After resetting the float heights it was not refilling the bowl quick enough. It would like just die at full throttle. Low and behold the tech at APT says it is very touchy setting the float height while still maintaining refill flow rate. The carb was real lean compared to a normal carb on the bottom end. Seemed to breath fresh air into riding in first and second gear. This prompted me into getting a 40mm billet for myself. Put her on and got her started. Seemed to be just a tad to lean so I proceeded to richen the clicker every couple hours fearing I was going to seize her up at WOT. From 1/2 to full throttle there was a stumbling spot. I contacted APT and requested a richer Fuel Metering Rod or FMR.
Received a new 76 FMR a couple weeks later and put it in to replace the leaner 78 FMR. I did not write down how many clicks I had the clicker set at. I was instructed to get the bike started going about 50 to 60 clicks from full rich. Then keep going leaner until the idle started to get angry. Like when your bike is running out of gas. It will rev up for awhile and then come back down a little and repeat. Once the idle gets a little angry you then set it 2-3 clicks richer until you have a perfect idle. Once you get a perfect idle you can then drop the idle speed down to where you like it at.
I was really excited now the FMR was richer and I hope to get the stumbling out of the 1/2 throttle area. Went out for the usual dune ride at Winchester bay. Was great 0 to 1/2 throttle. Was stumbling still at 1/2 throttle. When full throttle was achieved she ran great. I was still not sure what was causing her to stumble. Rode the rest of the day and figured I would ask questions on Monday. Kyle Burns put it this way summarizing where the clicker works.
So I went 3 clicks richer the next weekend. I get to the dunes and go to start her up and she just won't start. I notice gas dripping out of the header pipe. Had someone pull start me. Had to get pulled around the parking lot but would not start until I let off the throttle completely and just barely fired. It gets going and I go for another dune ride. After coming back and having a beer and refueling I go to start up again. Won't start. So I do the pull start thing again. Same results, like it was flooded. Went for another ride and same scenario. Was making chirping noises under full throttle. Like metal on metal as the train goes by. Would not start again after cooling down in the parking lot. Seemed strange if you stopped out on the dunes for a minute she would start right back up when hot. Loaded her back up and went home.
The next week I took the seat off and double checked the boot was sealing around the intake manifold. It seemed a little loose when I checked it out riding the weekend before and tightened the clamp. My thoughts were maybe it was loose and moved on me. After loosening and trying to move the carb forward I tightened it back up and turned 3 clicks richer, it actually started. Thought maybe it would not start due to extreme lean condition as stated in the manual.
Tried again the next weekend. Again the bike won't start so I got a pull start. Each time coming back for more fuel I just let her idle instead of hitting the kill switch. Just turned the idle up a bit. I had noticed after setting my idle at home I had to turn it up after getting to the dunes the last couple weekends. I went and gave her 3 clicks richer and was going to go do a plug check. As I got to 1/2 throttle just to about 3/4 open the piston froze up. SOB, did I go 3 clicks the wrong way? I got off the bike and started pushing her back to the parking lot. A guy rides up and asks me if I am out of gas. I look at him and say "I Wish" As I was sitting there waiting I kicked and the piston broke loose. Zero compression.
I'm like :wtf?:
APT says if the carb is hitting the frame it vibrates the carb not allowing it to atomize the fuel correctly. This week Kyle or Ryan was saying this creates a lean condition. So I went and took pics to show no frame touching.
Measuring from the carb to the intake is 3/4" in this pic
I then removed the boot and set it back to 3/4"
Now you can see the carb is touching the intake on the far side. This indicates to me that the carb touching the motor may do the same thing as the carb touching the frame. Even though no one mentioned this as a possibility. Heres a better pic so you can see how hard it is touching. The black sharpie line is where the boot was on the intake. It was up tight against the carb.
The plug is tan at piston freeze. I took this pic as I was taking the cylinder off.
So the whole time starting February until now (November) the carb has been experiencing the lean condition intermittently? (every 5 minutes) I am guessing. Seems the aluminum has been eaten away on the exhaust side of the piston.
pumashine, I have replied to this twice but doesn't come up on the main forum and others are asking about it. Perhaps it was all the pictures, so I've removed them in this reply. I'm not sure how you were able to see it and others were not so I'll post again.
It's clear from your pictures, especially the color/condition of the spark plug that the mixtures were pretty close to optimum, (light tan, mocha) and did not cause the localized overheating and ultimate seizure of your piston. I believe the evidence suggests that the front spigot of the carburetor touching the intake manifold was enough to shake the snot out of the carburetor and aerate the fuel to cause a critical lean condition in the mid to top. As I suggested in the two earlier posts and in your PM last night that after you rebuild your engine and clearance the intake manifold I would suggest you inspect the fuel inlet needle and seat for damage and replace if necessary. I further suggest that this was also the cause of the intermittant flooding and hard starting issues you had prior to the seizure and the float needle/seat wasn't doing well with all the shaking. I apologize to everyone here if you were not able to see this reply as it was my first post and the idea was to come on here to offer suggestions and advice. I thought this post was under review by moderators before other posts otherwise I would have waited to address other questions/concerns. Chris thank you for letting me know you were not able to see the post. Corey
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Testing, testing, testing, testing and using the process of elimination can only answer this question. A fully instrumented bike with data loggers while testing riding in the real world, is the only way I have been able to solve these types of problems when doing consulting for engine manufactures.
Sometimes all that needs to be done is change the riding style (the throttle position and RPM) to that for which the engine was designed. Two stroke engines that have been developed to medium to high levels of power output should not be used for just cruising around because of detonation related issues due to poor scavenging. This is the main reason manufactures pulled the plug on large two stroke street bikes. It was not because of emissions like most of the world believes.
I believe you mean light load misfiring and not detonation. The typical "four stroking" you hear with a high performance two stroke at light loads is caused by the engines inability to adequately clean (scavenge) the cylinder of the previous exhaust residuals and the engine has to pump the cylinder clean until a charge of adequate density is able to fire off. And this is most definitely a major contributor to high hydrocarbon emissions released from modern two strokes. What is interesting is that the very fine atomization of the SC dramatically dimiinshes this light load misfiring as the extra surface area of the finely atomized fuel will light off more easily. This also correlates to large reductions in emissions and big gains in fuel economy.
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Corey, aka SmartCarb, thanks for taking the time to come on the forum and offer help and explanations. This forum is all about helping one another and the sharing of helpful information, especially when it comes to something that we all love and enjoy so much, 250R's. I know that you are really busy with dyno testing and other activities right now, but if you get the chance, I would love for you to start a new thread where you could speak about the differences between the SmartCarb design and the older Lectron design just from a perspective of why they are different and not necessarily mentioning why one is better than the other. For example, when we spoke on the phone, you mentioned how the Lectron relies heavily on various compound tapers of the needle to change the supply of the fuel where as the SmartCarb is designed with a different shape throat to rely more heavily on the signal of the engine and not on various compound tapers of needles. This being the reason that 90% of the SmartCarbs on the market have the same taper needle. We also talked about how the pressurized fuel bowl acts like a powerjet already. And how a richer fuel metering rod (FMR) is really used more for diminished signal at WOT. Could you elaborate on these things?
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This is a great thread. Very informative
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pumashine, I have replied to this twice but doesn't come up on the main forum and others are asking about it. Corey
I apologize Corey as I did not see the post was moderated last night. I just now approved the first post but will leave the second out. I am a moderator on this forum so I see what others do not. Thank you for coming to the forum to answer the question of what my problem is and explain how the carb functions. I have spoke to Tom and he helps out as you are busy. I ran Doug Patterson's 40mm billet for a few rides on the dunes. The carb was flooding when I got it and set the float height. But I guess it also effected the refill rate at the same time as it was running out of fuel in about 5 seconds at full throttle. Back then I was experiencing a lean misfire at about 1/2 throttle or more. I have run the carb from lean to rich a good 20 clicks either side of the factory setting. After putting in the richer FMR I was still experiencing the lean misfire right before full throttle. It would then clear up just as it did with the factory FMR at 3/4 to full throttle. As I learned Kyle Burns was having a hard time getting rich on the top end then he mentioned the carb was hitting the frame. By this time it was too late. I had been running a good 20 hours of time with the carb hitting the motor. Got a new piston coming Friday and my new Intake manifold will be in next week. I will take the carb apart and inspect it. Proly just put the second new one in to make sure as it has the factory FMR I believe.
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Corey, aka SmartCarb, thanks for taking the time to come on the forum and offer help and explanations. This forum is all about helping one another and the sharing of helpful information, especially when it comes to something that we all love and enjoy so much, 250R's. I know that you are really busy with dyno testing and other activities right now, but if you get the chance, I would love for you to start a new thread where you could speak about the differences between the SmartCarb design and the older Lectron design just from a perspective of why they are different and not necessarily mentioning why one is better than the other. For example, when we spoke on the phone, you mentioned how the Lectron relies heavily on various compound tapers of the needle to change the supply of the fuel where as the SmartCarb is designed with a different shape throat to rely more heavily on the signal of the engine and not on various compound tapers of needles. This being the reason that 90% of the SmartCarbs on the market have the same taper needle. We also talked about how the pressurized fuel bowl acts like a powerjet already. And how a richer fuel metering rod (FMR) is really used more for diminished signal at WOT. Could you elaborate on these things?
The Lectron and the SmartCarb are each a very fine example stemming from the original Edmonston designed single circuit flat slide carburetor. The distinctions however between the Lectron and the SmartCarb span nearly 45 years of development with no less than five other varieties in between. These less known iterations include the EI Blue Magnum, the Daytona Quicksilver I and Quicksilver II's, Edelbrock Quicksilver, AFT and finally theSmartCarb.
William H. "Red" Edmonston and I were partners at the time of his passing and most of the development work for the SmartCarb took place at the University of Wyoming in our 2 stroke research and development laboratories. Red clearly understood the limitations of a single circuit system and the fundamental flaw imposed by a more or less round throat venturi. The trough or valley at the bottom of an Edmonston designed venturi was quite well understood by this time and it can be found on a Lectron. It is this feature that led to what was really the beginning of our understanding the importance of concentrating and accelerating as much of the actual airflow through the venturi, right at the base of the metering rod and nozzle interface as possible, at all throttle positions. In a more or less round venturi, the rate of throttle opening from idle to half open is exponentially divergent, meaning it’s getting much larger, faster, the farther you open it. From half to wide open, however, the lines of the circle are converging and the rate of opening is slowing even though you are now almost wide open. This causes the pressures through the venturi to swing wildly as you move the throttle slide bottom to top and vice versa, which in turn causes the signal to the metering rod to fluctuate, and unless corrections are made by altering the angle of the metering rod crisp throttling and consistent fueling suffers.
(Signal referred to here is the negative value created by the piston displacing air as the engine cycles, creating a pressure drop within the venturi as air rushes in, thus allowing atmosphere to push fuel up through the nozzle, past the surface of the metering rod and into the intake airstream. In the case of a metering rod carburetor this signal is also read by the flat of the metering rod which creates another secondary low pressure zone.)
The difficulty of putting very accurate changes in angle along a 1/8” surface of a metering rod is maddening and is Lectron’s biggest challenge. This is one reason Lectrons are most noted as a drag racing carburetor and was a place they were found to work really well. Today I do believe they have made tremendous progress in metering rod development and the addition of a power-jet has made their job a little easier. IF all the angles are correct, for the right engine, and the PJ is set correctly they work really well through the whole range much better than a conventional carburetor.
Red felt the better solution was to shape the venturi as such that we could maintain an even pressure against the metering rod through the whole range of throttling. The question was how to do that without giving up a lot of flow and limit the carb’s full potential size for size. He understood laminar flow very well and we did a lot of experimenting with lead in curves to control airflow and get the carburetor to gulp a lot of air, even though the neck of the venturi was unconventionally restrictive. We also added a nose to the slide to further direct and compress airflow leading into the metering rod. What really tipped the scales technology wise though is the ambient air density correction circuit and how it interrelates to the venturi. Most people understand this to be the altitude correction circuit, which it is, but it is really much more. It provides an instantaneous dynamic balance between the pressures the throat of the carburetor is actually seeing and the ambient air pressure against the top of the fuel in the float bowl in all conditions. Perhaps a more familiar term people recognize for this effect is Manifold Absolute Pressure and is something that all modern closed loop EFI systems rely on for correcting air/fuel ratios with changes in ambient air density. Apart from the venturi shape this feature alone is what allows the SmartCarb to only need a single angle grind metering rod, and in most cases a common grind across a very large variety of products and applications. This circuit also acts much like a power jet at the very top end when the static pressure being applied to the fuel in the float bowl also becomes dynamic and liquid flow lift ensues, hammering fuel up the nozzle directly proportional to total flow through the venturi. This is actually much superior to a power jet in that it remains finely atomized, because it is after all still using the main (and only) circuit, whereas a power-jet is literally throwing fuel on the fire and is emitted as almost pure liquid when it enters high into the air stream. This isn’t the worst thing, however it does dramatically affect Lectron’s full potential for fuel economy gains, altitude compensation and emissions reductions and it effectively makes it yet another multi circuit carburetor.
The drawback to the SmartCarb air density correction circuit is lack of a float bowl overflow and the necessity of tip over valves, along with the additional problems they create. The performance benefits the system offers are more than worth the effort though and the tip over valves, along with additional functionality to further protect our patents for the scoop and venting system, offer a very desirable side benefit in that now the carburetori s completely sealed. Certification testing shows the SC to be the lowest evaporative emissions carburetors ever test. Plus there is no raw fuel spillage on the ground and it fits very conveniently into the new epa tip over ruling for motorcycles. Who’d of known they were about to implement that? We are continuing to improve the system and are implementing changes to eliminate sticking issues.
With all of that said, I have just one more thing. Make no mistake, Lectron is not our competition. Our competition is all modern fuel systems worldwide, electronic or mechanical. Here’s why; any emissions reduction strategy requires a fuel system that is able to two things very well. Finely atomize fuel and maintain extremely accurate air/fuel ratios. TheSmartCarb simply does those two things better than anything else we currently know of period, and it does it without electronics. For instance we are in the second leg of EPA Tier II and ARB on road emissions certification for Zaeta’s TM powered 530 DT motorcycle (google it). This is TM’s open enduro race 4t engine they have attempted to prior certify in North America themselves. They have tried twice , both times using two precious metal catalysts and a race TMXX Mikuni downdraft, both times unsuccessful. APT is actually touching on Euro III numbers with this bike and is passing EPA and ARB easily with just our new 40mm side pull FCR replacement carburetor and no cats. In fact we are under Tier II CO emissions by nearly 90% and HC and Nox 38% and 16% respectively all this with a 28% gain in fuel economy. This is no joke and these aren’t the types of things you are hearing about in the forums and possibly in a lot of people’s minds on a performance related forum this may not seem like a big deal at all. But actually it is everything.
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I apologize Corey as I did not see the post was moderated last night. I just now approved the first post but will leave the second out. I am a moderator on this forum so I see what others do not. Thank you for coming to the forum to answer the question of what my problem is and explain how the carb functions. I have spoke to Tom and he helps out as you are busy. I ran Doug Patterson's 40mm billet for a few rides on the dunes. The carb was flooding when I got it and set the float height. But I guess it also effected the refill rate at the same time as it was running out of fuel in about 5 seconds at full throttle. Back then I was experiencing a lean misfire at about 1/2 throttle or more. I have run the carb from lean to rich a good 20 clicks either side of the factory setting. After putting in the richer FMR I was still experiencing the lean misfire right before full throttle. It would then clear up just as it did with the factory FMR at 3/4 to full throttle. As I learned Kyle Burns was having a hard time getting rich on the top end then he mentioned the carb was hitting the frame. By this time it was too late. I had been running a good 20 hours of time with the carb hitting the motor. Got a new piston coming Friday and my new Intake manifold will be in next week. I will take the carb apart and inspect it. Proly just put the second new one in to make sure as it has the factory FMR I believe.
Your problem could have easily been overlooked by anybody. Glad we have things beginning to narrow down and once you get things back up and running I'm certain you will be very pleased with the results. I do believe the factory metering rod should be correct for the application, however the richer MR would offer an additional buffer for when you break it in or if you get wild with the rebuild and change some things in the mean time.
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Longest technical post ever. Thank you. Welcome to 250R.Org
We are a passionate two stroke enthusiast group here to exchange knowledge. I hope you will make your presences known often.
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Longest technical post ever. Thank you. Welcome to 250R.Org
We are a passionate two stroke enthusiast group here to exchange knowledge. I hope you will make your presences known often.
:redbull:
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I believe you mean light load misfiring and not detonation. The typical "four stroking" you hear with a high performance two stroke at light loads is caused by the engines inability to adequately clean (scavenge) the cylinder of the previous exhaust residuals and the engine has to pump the cylinder clean until a charge of adequate density is able to fire off. And this is most definitely a major contributor to high hydrocarbon emissions released from modern two strokes. What is interesting is that the very fine atomization of the SC dramatically dimiinshes this light load misfiring as the extra surface area of the finely atomized fuel will light off more easily. This also correlates to large reductions in emissions and big gains in fuel economy.
I was not referring to four stroking (miss-fire) at light loads (small throttle openings) when the RPM is low and the engine is off the pipe I was referring to the detonation that is inherent with highly developed two-strokes when the RPMs are high and the engine is on the pipe, the throttle opening is low, and the resulting crankcase filling is minimal. When these three conditions occur simultaneously, short-circuiting of the fresh charge occurs, the cylinder is not scavenged sufficiently, and too much residual exhaust is mixed with the fresh charge. When enough fresh charge is trapped with the exhaust residuals, the residual exhaust often raises the temperature of the remaining fresh charge to the point that it is prone to detonate during the combustion event.
When short-circuiting occurs, HCs are increased even when a combustion event occurs at the end of the current cycle. HCs are increased even more when a misfire occurs regardless of what caused the misfire.
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Tony I hate to see you spend more money but if I were you before Arlen sends that piston to you get him to send you one of his air filter set ups and ditch that stock 250r air boot and air box. I noticed a difference in performance when I installed his setup I think the stock stuff is restrictive on your large motor. The filter size is 1.5 times larger with his these big motors need air
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Tony I hate to see you spend more money but if I were you before Arlen sends that piston to you get him to send you one of his air filter set ups and ditch that stock 250r air boot and air box. I noticed a difference in performance when I installed his setup I think the stock stuff is restrictive on your large motor. The filter size is 1.5 times larger with his these big motors need air
There is 2 hp on a national level 250 when you get the tuned length right and an air filter that has adequate surface area over that of a stock airbox with a K&N with the lid off. I would expect even larger gains with an engine that is over 150 cc larger.
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There is 2 hp on a national level 250 when you get the tuned length right and an air filter that has adequate surface area over that of a stock airbox with a K&N with the lid off. I would expect even larger gains with an engine that is over 150 cc larger.
Does the tuned length differ from a 250cc to a 430cc motor?
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Does the tuned length differ from a 250cc to a 430cc motor?
I have not tested different intake system lengths on the Dyno for the 430. If the power peak and torque peaks occur at about the same RPM on the 430 as the 250, I would expect the tuned length of the intake system to be similar. The exhaust pipe has the major influence on the RPM of where the peaks occur.
If you are using a "250" pipe with a larger stinger and larger silencer core, a 250 intake would probably be an improvement.
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I feel like I just stayed at a Holiday in last night!
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I was not referring to four stroking (miss-fire) at light loads (small throttle openings) when the RPM is low and the engine is off the pipe I was referring to the detonation that is inherent with highly developed two-strokes when the RPMs are high and the engine is on the pipe, the throttle opening is low, and the resulting crankcase filling is minimal. When these three conditions occur simultaneously, short-circuiting of the fresh charge occurs, the cylinder is not scavenged sufficiently, and too much residual exhaust is mixed with the fresh charge. When enough fresh charge is trapped with the exhaust residuals, the residual exhaust often raises the temperature of the remaining fresh charge to the point that it is prone to detonate during the combustion event.
When short-circuiting occurs, HCs are increased even when a combustion event occurs at the end of the current cycle. HCs are increased even more when a misfire occurs regardless of what caused the misfire.
Gotcha. I must have misinterpreted your earlier statement, it was the "just cruising around" that threw me.
Testing, testing, testing, testing....
Two stroke engines that have been developed to medium to high levels of power output should not be used for just cruising around because of detonation related issues due to poor scavenging.
Please explain your findings to us a little more in detail of how detonation occurs in a high performance two stroke due to poor scavenging. Being that detonation in a spark-ignition internal combustion engine occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. (WIKI)
If I'm understanding you correctly you are saying that at high rpm, the throttle is low enough to not adequately fill the crankcase and the pipe is over scavenging the cylinder enough to cause short-circuiting by pulling the bulk of the fresh charge out the pipe? Because the cylinder is unable to completely clear the residual exhaust gases, the temperature of the residual exhaust gases cause the fresh charge to rise to the point of what? Preignition? That is an entirely different animal and according to this logic would be only thing that could potentially occur if there were enough heat energy left in the exhaust gases to overcome the bulk cooling effect of filling the cylinder with fresh charge. In a loop scavenged two stroke the bulk transfer of the intake gases is what begins exhaust movement out of the cylinder and in a good engine the wave front in the pipe will have reached the end of the diffuser section and a strong negative pressure is being exerted on the cylinder to pull out exhaust and haul fresh mix up from the crankcase. Exhaust residuals dilute the fresh charge and could in no way contribute to detonation.
Modern large bore ultra high performance two stroke engines with power valve exhaust do a very good job of charging and recharging the cylinder (scavenging). Its really only when you are off the pipe that any real short-circuiting occurs. Short-cicuiting referring to fresh charge that escapes out the exhaust port due to insufficient back wave to push the charge back in the cylinder just before exhaust port closing. Large bore snowmobile and PWC two strokes often approach 4 hp per cubic inch in factory trim. Piston port or rotary valve GP engines of yesteryear could possibly have had problems with just cruising speeds and low throttle settings to cause detonation due to insufficent bulk flow scavenging, but today's 2t's with state of the art combustion chambers and boost ported cylinders are very efficient and the evidence is clear simply by the incredible power they make and the power they make over a reasonably broad torque curve.
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I like my smartcarb, just saying
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I have not tested different intake system lengths on the Dyno for the 430. If the power peak and torque peaks occur at about the same RPM on the 430 as the 250, I would expect the tuned length of the intake system to be similar. The exhaust pipe has the major influence on the RPM of where the peaks occur.
If you are using a "250" pipe with a larger stinger and larger silencer core, a 250 intake would probably be an improvement.
the well tuned 250 stuff i seen had peak hp at nearly 11k rpm. i imagine a engine of 400+cc would be a fair bit lower, for reliability sake anyways. one time hooked a digital rpm unit on a engine about 500cc. sounded like it was gonna blow up at 10k
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Large bore snowmobile and PWC two strokes often approach 4 hp per cubic inch in factory trim.
thats not bad, all things considered, and with the new technology theyre using. i have a idea for a twin cylinder engine totalling 500cc. if it ever makes it to fruition i estimate about 4.5 hp per CI or .28 per cc, using gas and a standard keihin or mukini style carb and no fancy electronics of any kind. seems like the size of your wallet is always the determing factor :highly_amused:
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the well tuned 250 stuff i seen had peak hp at nearly 11k rpm. i imagine a engine of 400+cc would be a fair bit lower, for reliability sake anyways. one time hooked a digital rpm unit on a engine about 500cc. sounded like it was gonna blow up at 10k
You must be looking at 250 shifter kart engines that are being twisted to around 11000 rPM. The TRX 250 R engines and pipes that we used on the national outdoor and stadium events usually made their peak power at under 9000 RPM.
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thats not bad, all things considered, and with the new technology theyre using. i have a idea for a twin cylinder engine totalling 500cc. if it ever makes it to fruition i estimate about 4.5 hp per CI or .28 per cc, using gas and a standard keihin or mukini style carb and no fancy electronics of any kind. seems like the size of your wallet is always the determing factor :highly_amused:
Snowmobile engines do not usually have their power over as wide of an RPM range as engines with transmissions. It is a lot easier to make huge peak power numbers if you do not need it over a wide RPM range. The CVT can hold the engine at it's peak power.
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yes i know snomo engines are a different breed because of the transmission system. try riding a snomo type of powerband with a conventional transmission :excitement: :excitement:
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I believe pre-ignition is what starts the chain of events leading to detonation in the cylinder during high rpms and part throttle.
In this situation you are no longer filling the crankcase completely, this will lower the crankcase pressure which means the cylinder gases are more prone to back fill into the transfers and pre-heat the tunnels and fresh mixture. This not as much of a issue at lower rpms because the exhaust port has more time to effectively bleed the pressure down but as rpms increase the time for this to happen shortens.
I do know that Aprilla forbid their racers from doing victory burnouts at the end of the race because of the motors violently detonating and seizing from spinning the tire at high rpms and low throttle positions, these same bikes could run WOT on the dyno and track until the tank would run dry without any issues.
I also owned a 700 arctic cat snowmobile that when in the same type of situation was very prone to siezing, that motor was bullet proof, unless you just cruised at very small throttle postions for a extended period of time, now you could say well it was just lean in that area, but according to guys on the dyno that checked fuel rates they were not really that bad so I suspect the pre-ignition condition stemming from the pre-heated fresh fuel charge was to blame.
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Snowmobile engines do not usually have their power over as wide of an RPM range as engines with transmissions. It is a lot easier to make huge peak power numbers if you do not need it over a wide RPM range. The CVT can hold the engine at it's peak power.
The CVT is just another transmission, although to your point it does maintain a more or less constant shift speed. However anyone who has ridden a modern snowmobile in the mountains and the tractability new machines offer will recognize immediately new 2t engines do indeed have impressive performance, broad torque curves, and nice stable combustion when you are low in the power band and executing tight maneuvers. Peak RPM typically being around 8200 RPM. Hillclimb and Snowcross racing also show this to be true. Wobbley has been building SC equipped GP twin 2t race engines in New Zealand/Australia for years and we have one in our pikes peak quad. Pikes Peak is now completely paved and the torque necessary to power out of an 11% grade uphill corkscrew at race pace is pretty severe (manual 6 spd). The broad usable power of a state of the art two stroke is certainly an improvement over the hyper light switch engines of years ago. Could these engines once again be made available for on street use and become emissons compliant? Yes. Is there politics against their use? Yes, it's all about emissions, however DFI 2ts and our SF-II engines are showing it is certainly possible. We test at ARB and EPA cert labs several times a year and have our own emissions certifcation laboratory. One thing is clear, the EPA does not care what the operating system of the engine is (2t or 4t) doesn't matter as long as it passes their numbers for emissions and noise. But those numbers are getting much more stringent and harder to meet.(http://i1364.photobucket.com/albums/r726/coreyd396/DSC00954_zpsd6cc1eb3.jpg)
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I believe pre-ignition is what starts the chain of events leading to detonation in the cylinder during high rpms and part throttle.
In this situation you are no longer filling the crankcase completely, this will lower the crankcase pressure which means the cylinder gases are more prone to back fill into the transfers and pre-heat the tunnels and fresh mixture. This not as much of a issue at lower rpms because the exhaust port has more time to effectively bleed the pressure down but as rpms increase the time for this to happen shortens.
I do know that Aprilla forbid their racers from doing victory burnouts at the end of the race because of the motors violently detonating and seizing from spinning the tire at high rpms and low throttle positions, these same bikes could run WOT on the dyno and track until the tank would run dry without any issues.
I also owned a 700 arctic cat snowmobile that when in the same type of situation was very prone to siezing, that motor was bullet proof, unless you just cruised at very small throttle postions for a extended period of time, now you could say well it was just lean in that area, but according to guys on the dyno that checked fuel rates they were not really that bad so I suspect the pre-ignition condition stemming from the pre-heated fresh fuel charge was to blame.
Large bore engines have all kinds of ways to create localized hot spots and plenty of time for detonation to occur. Pre-ignition and detonation are two completely different things. Pre-igntion- being auto ignition, where the mixture torches off before the plug has a chance to light it. Detonation being a separate combustion event occuring as the initial flame front (lit by the spark plug) pre heats the end gases in front of it to the point of auto ignition (active radical combustion) and the two or more flame fronts collide and produce the characteristic knock of detonation. I think just hung up on terminology and to be fair I'm sure your thoughts are fairly correct in the context to which you are referring. Anyway back to the carburetor.
Looks like Lectron runs power jets on their carbs.
http://www.lectronfuelsystems.com/carburetor/
(http://trx250r.org/attachment.php?attachmentid=6896&d=1416266213)
I wonder if one could be adapted to the smart carb?
This is from their FAQ:
"Should I have a power jet carburetor or not?
This is a must for a two stroke engine. We prefer to have them on all types of engines two or four stroke.
The power jet carburetor can give you a wider range on tuning and also helps you fine tune top end power on all types of engines."
"What does the power jet do for tuning?
The power jet is for high speed tuning only. The power will kick in about 3/4 from top RPM First get the motor running good at idle and mid-range then work on the power jet.
The power jet will not effect the tuning of idle, mid-range, or response on the carburetor."
The SC does not need a power-jet. The float bowl pressurization circuit is a much more effective way to control top end fueling and provides the same very fine atomization as the rest of the range. At the very top end of RPM's the pressure being exerted against the fuel in the float bowl begins to move from static pressure into dynamic liquid flow and fuel is being squirted up the nozzle by the 200+ MPH air pressure being rammed into the scoop. The real beauty is that the forces driving the fuel are exactly proportional to the air pressure flowing into the engine. Same applies for adding boost.
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I have read the the definitions of pre-ignition and detonation and understand they are different, but I have always suspected that you get to a point where one leads to the other but occur in separate strokes, meaning the pre-ignition probably builds enough heat in the piston, cylinder and combustion chamber to create local hot spots that may start detonation on the next compression stroke. Whether it continues to detonate I am not sure but if the conditions are ripe for pre-ignition to happen then it just may go back to lighting off the fuel before the spark.
So since you do not feel a powerjet is needed because of the float bowl pressurization circuit and a compound angle needle is not needed to fix a lean condition on the top end how are you going to increase the fuel on the topend without over richening the bottomend mixture
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I have read the the definitions of pre-ignition and detonation and understand they are different, but I have always suspected that you get to a point where one leads to the other but occur in separate strokes, meaning the pre-ignition probably builds enough heat in the piston, cylinder and combustion chamber to create local hot spots that may start detonation on the next compression stroke. Whether it continues to detonate I am not sure but if the conditions are ripe for pre-ignition to happen then it just may go back to lighting off the fuel before the spark.
Completely agree, there will forever be nuances that escape our attention and like my Dad always used to say, nobody's ever been inside one while it's running. Probability suggests that yes the two phenomena could certainly overlap and this may very well be the reason a lot of people are confused by the differences.
So since you do not feel a powerjet is needed because of the float bowl pressurization circuit and a compound angle needle is not needed to fix a lean condition on the top end how are you going to increase the fuel on the topend without over richening the bottomend mixture
Exactly the way we do it now, run a steeper grind on the metering rod to add fuel mid to top, then set the clicker in a slightly lower setting than the leaner rod you just took out, to hit your target idle/tip-in mixture values. Then ride it like you stole it.
EDIT: The SC is almost completely signal based and in a lot of cases is fairly indifferent to the metering rod as long as it's not critically too lean. The range of metering rods we have ever used in the 36,38 and 40mm carbs, with exception of alcohol, nitro, boosted and a few odd applications, amounts to four sizes. All the same grind length, (we did toy with some shorter rods (same grinds) when the cast 38s came out, but results were not as favorable as we hoped and we resorted back to the longer rods which are the same as the billets). 082", .080", .078" and .076" tip thickness - 2.357" grind on a 3.583" metering rod.
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The Lectron and the SmartCarb are each a very fine example stemming from the original Edmonston designed single circuit flat slide carburetor. The distinctions however between the Lectron and the SmartCarb span nearly 45 years of development with no less than five other varieties in between. These less known iterations include the EI Blue Magnum, the Daytona Quicksilver I and Quicksilver II's, Edelbrock Quicksilver, AFT and finally theSmartCarb.
William H. "Red" Edmonston and I were partners at the time of his passing and most of the development work for the SmartCarb took place at the University of Wyoming in our 2 stroke research and development laboratories. Red clearly understood the limitations of a single circuit system and the fundamental flaw imposed by a more or less round throat venturi. The trough or valley at the bottom of an Edmonston designed venturi was quite well understood by this time and it can be found on a Lectron. It is this feature that led to what was really the beginning of our understanding the importance of concentrating and accelerating as much of the actual airflow through the venturi, right at the base of the metering rod and nozzle interface as possible, at all throttle positions. In a more or less round venturi, the rate of throttle opening from idle to half open is exponentially divergent, meaning it’s getting much larger, faster, the farther you open it. From half to wide open, however, the lines of the circle are converging and the rate of opening is slowing even though you are now almost wide open. This causes the pressures through the venturi to swing wildly as you move the throttle slide bottom to top and vice versa, which in turn causes the signal to the metering rod to fluctuate, and unless corrections are made by altering the angle of the metering rod crisp throttling and consistent fueling suffers.
(Signal referred to here is the negative value created by the piston displacing air as the engine cycles, creating a pressure drop within the venturi as air rushes in, thus allowing atmosphere to push fuel up through the nozzle, past the surface of the metering rod and into the intake airstream. In the case of a metering rod carburetor this signal is also read by the flat of the metering rod which creates another secondary low pressure zone.)
The difficulty of putting very accurate changes in angle along a 1/8” surface of a metering rod is maddening and is Lectron’s biggest challenge. This is one reason Lectrons are most noted as a drag racing carburetor and was a place they were found to work really well. Today I do believe they have made tremendous progress in metering rod development and the addition of a power-jet has made their job a little easier. IF all the angles are correct, for the right engine, and the PJ is set correctly they work really well through the whole range much better than a conventional carburetor.
Red felt the better solution was to shape the venturi as such that we could maintain an even pressure against the metering rod through the whole range of throttling. The question was how to do that without giving up a lot of flow and limit the carb’s full potential size for size. He understood laminar flow very well and we did a lot of experimenting with lead in curves to control airflow and get the carburetor to gulp a lot of air, even though the neck of the venturi was unconventionally restrictive. We also added a nose to the slide to further direct and compress airflow leading into the metering rod. What really tipped the scales technology wise though is the ambient air density correction circuit and how it interrelates to the venturi. Most people understand this to be the altitude correction circuit, which it is, but it is really much more. It provides an instantaneous dynamic balance between the pressures the throat of the carburetor is actually seeing and the ambient air pressure against the top of the fuel in the float bowl in all conditions. Perhaps a more familiar term people recognize for this effect is Manifold Absolute Pressure and is something that all modern closed loop EFI systems rely on for correcting air/fuel ratios with changes in ambient air density. Apart from the venturi shape this feature alone is what allows the SmartCarb to only need a single angle grind metering rod, and in most cases a common grind across a very large variety of products and applications. This circuit also acts much like a power jet at the very top end when the static pressure being applied to the fuel in the float bowl also becomes dynamic and liquid flow lift ensues, hammering fuel up the nozzle directly proportional to total flow through the venturi. This is actually much superior to a power jet in that it remains finely atomized, because it is after all still using the main (and only) circuit, whereas a power-jet is literally throwing fuel on the fire and is emitted as almost pure liquid when it enters high into the air stream. This isn’t the worst thing, however it does dramatically affect Lectron’s full potential for fuel economy gains, altitude compensation and emissions reductions and it effectively makes it yet another multi circuit carburetor.
The drawback to the SmartCarb air density correction circuit is lack of a float bowl overflow and the necessity of tip over valves, along with the additional problems they create. The performance benefits the system offers are more than worth the effort though and the tip over valves, along with additional functionality to further protect our patents for the scoop and venting system, offer a very desirable side benefit in that now the carburetori s completely sealed. Certification testing shows the SC to be the lowest evaporative emissions carburetors ever test. Plus there is no raw fuel spillage on the ground and it fits very conveniently into the new epa tip over ruling for motorcycles. Who’d of known they were about to implement that? We are continuing to improve the system and are implementing changes to eliminate sticking issues.
With all of that said, I have just one more thing. Make no mistake, Lectron is not our competition. Our competition is all modern fuel systems worldwide, electronic or mechanical. Here’s why; any emissions reduction strategy requires a fuel system that is able to two things very well. Finely atomize fuel and maintain extremely accurate air/fuel ratios. TheSmartCarb simply does those two things better than anything else we currently know of period, and it does it without electronics. For instance we are in the second leg of EPA Tier II and ARB on road emissions certification for Zaeta’s TM powered 530 DT motorcycle (google it). This is TM’s open enduro race 4t engine they have attempted to prior certify in North America themselves. They have tried twice , both times using two precious metal catalysts and a race TMXX Mikuni downdraft, both times unsuccessful. APT is actually touching on Euro III numbers with this bike and is passing EPA and ARB easily with just our new 40mm side pull FCR replacement carburetor and no cats. In fact we are under Tier II CO emissions by nearly 90% and HC and Nox 38% and 16% respectively all this with a 28% gain in fuel economy. This is no joke and these aren’t the types of things you are hearing about in the forums and possibly in a lot of people’s minds on a performance related forum this may not seem like a big deal at all. But actually it is everything.
Hi smartcarb. i am impressed by your technology. however, can you elaborate on your mentors understanding of laminar flow. reason i ask is, laminar flow has no place within the intake of an internal combustion engine. hi velocity and/or turbulent flow is what makes a typical carb atomize the way it does. is it your way to promote pressurization of the fuel flow that compensates for this? maybe within my query is the patented info.lol
john
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Hi smartcarb. i am impressed by your technology. however, can you elaborate on your mentors understanding of laminar flow. reason i ask is, laminar flow has no place within the intake of an internal combustion engine. hi velocity and/or turbulent flow is what makes a typical carb atomize the way it does. is it your way to promote pressurization of the fuel flow that compensates for this? maybe within my query is the patented info.lol
john
And therein lies the fundamental difference between the SC and every other predecessor. You need to understand Mikuni, Keihin and many others learned a lot of what we take for granted from Mr. Edmonston. He lived the remainder of his life competing against his own technology. Story goes though he's on a jet leaving Detroit shortly after selling Lectron to GM. It was raining with fog, he was watching the leading edge of the wing and of course with vapor we all can see laminar flow form as the airstream straightens itself and accerates over the leading edge and curve of the wing. Same thing with hearding the air into the throat of an SC, and years later we put it into practice. If you look closely you will see a decided curve leading into the venturi, this accelerates, straightens and begins to compress the air and greatly helps our cause to stuff more air through an otherwise fairly constrictive throat. Naturally, with any carburetor true to Bernoulli the idea is to create as high of a compression zone as possible without choking flow and causing stall, thereby increasing flow to maximum velocity and achieve the strongest venturi vacuum you can. Ok we all get that. To answer your question, it has always been understood that you want to create turbulence (mixture motion) along the intake to aid atomization and fuel suspension. This is only true however after the fuel has been introduced into the airstream and some surface roughness (not wall uneveness) helps keep everything mixing.
With the SmartCarb, we promote laminar flow as a means to create very high velocity and compression under the slide so that we can utilize a single fueling circuit. The atomization in an SC is created by the metering rod and not pre-emulsion through a pilot jet at idle and further emulsion though the nozzle at wide open, as it is with a conventional carburetor. In these carburetors any extra turbulence is welcome because they are so poor at atomization. With an SC because the fuel is delivered from the metering rod above the airstream, the fuel is carried as a vapor plume into the engine and doesn't need a lot of assistance to maintain suspension. Great news is this allows you to hog more air through your engine with an SC or run a slightly larger venturi and not suffer the all too easy consequences of flow stall, causing fuel to fall out of suspension. To a certain degree of course this happens in all engines, but the farther you can carry the bulk mix into the combustion chamber, the closer the actual trapped air/fuel ratios are to those as delivered by the carburetor. Then you really begin to narrow the gap with Direct fuel injection and the goal of minimizing fuel consumption is best served. Combine that with Kadenecy effect bulk transfer of the mix in modern two strokes and you see where this is all headed. Move further along with Sonic-Flow Engine tech with variable geometry plumbing and things really begin to look pretty bright and a new lease on uncomplicated 2t's may be coming along.
(http://i1364.photobucket.com/albums/r726/coreyd396/P1000293_zpscc72ce36.jpg)
(http://i1364.photobucket.com/albums/r726/coreyd396/103_zps38649232.jpg)
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thats not bad, all things considered, and with the new technology theyre using. i have a idea for a twin cylinder engine totalling 500cc. if it ever makes it to fruition i estimate about 4.5 hp per CI or .28 per cc, using gas and a standard keihin or mukini style carb and no fancy electronics of any kind. seems like the size of your wallet is always the determing factor :highly_amused:
Snowmobile engines do not usually have their power over as wide of an RPM range as engines with transmissions. It is a lot easier to make huge peak power numbers if you do not need it over a wide RPM range. The CVT can hold the engine at it's peak power.
I'll side track the topic a bit, sorry. All of my Mod sled motors make peak HP over 500+ rpm sweep just like mod ATV motors. Plus they are .30 hp per cc. A CVT can't just start at peak HP. Most start at 4500 ~ 5000 RPM then end at 9800 ~ 10,000 RPM. To tune a CVT and WIN takes alot more work then you think. I wouldn't use the word easier in any part of it. Your 60' time is everything and if your waiting to make power, you wont win. IMO it takes running 1.1's in 60' and a peaky motor wont turn that time
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46351 Wobbley has been building SC equipped GP twin 2t race engines in New Zealand/Australia for years and we have one in our pikes peak quad.(http://i1364.photobucket.com/albums/r726/coreyd396/DSC00954_zpsd6cc1eb3.jpg)
It's strange that you did mention wobbly, because I have only seen him mention the smart carb once and it was in reference to the pikes peak
Quad but he stated that he quit helping with development of it when his request for a adjustable power jet were ignored.
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I will say I do like the oviform shape of the SmartCarb and also the old PSI BigAir carb, this should work especially well at smaller throttle openings and never understood why the other carb manufacturers did not use it.
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I'll side track the topic a bit, sorry. All of my Mod sled motors make peak HP over 500+ rpm sweep just like mod ATV motors. Plus they are .30 hp per cc. A CVT can't just start at peak HP. Most start at 4500 ~ 5000 RPM then end at 9800 ~ 10,000 RPM. To tune a CVT and WIN takes alot more work then you think. I wouldn't use the word easier in any part of it. Your 60' time is everything and if your waiting to make power, you wont win. IMO it takes running 1.1's in 60' and a peaky motor wont turn that time
Well said. Most find stock to reasonably ported exhaust and longish tuners the answer for clutching nightmares in drag racing. Ski-Doo's TRA clutches also really help to compound torque out of the hole and has answered a lot of problems in stock class racing. Conversely, Polaris and Arctic Cat have the luxury of a compound overdrive but take a lot more finesse to beat a rotax in 660ft. But you'll see them gaining mid track every time. We were desperate enough to keep from pulling the belt in half on our 340 and 440 sno pro rotax's back in the day we made a slipper clutch for the jackshaft so we could leave the line with the clutches and belt already engaged. 6800-12,500 rpm. Worked pretty good until one came apart and did a number on my left foot, finally relented and added 7/8" to the head pipes and 145 deg. rotary plates. Sad though if you've ever heard one at full song, they never sounded the same after that, but were much quicker in 60ft times.
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It's strange that you did mention wobbly, because I have only seen him mention the smart carb once and it was in reference to the pikes peak
Quad but he stated that he quit helping with development of it when his request for a adjustable power jet were ignored.
Except Rob Berrington-Smith has been racing with them for two seasons http://m.youtube.com/watch?v=7Ve2Y86dP7U
Jeram on twostrokemotocross forum posted this recently http://twostrokemotocross.com/forum/technical/apt-smart-carb/
I spoke to Wobbly (Honda NSR500 GP technicial) back in late January.
He had tested the billet SmartCarbs and he said he thinks theyre unreal.
To be clear. Wobbly was not, has not, been helping with the development of the SC, and as far as I have spoken with him, he has never requested a power-jet. We have sent him different metering rods to try over time. Perhaps if you could reference where you heard that would be interesting to know. He built the pipes for the quad in the picture and advised Wilson Performance on the Cheetah cylinders. I sold him the 40's off the quad and a 28mm for his bucket 50cc. The 40s have been running on Wobbly's RZ400 ridden by Rob Berrington-Smith. Wobbly would like to be our distributor down under and I think his only problem with the SmartCarb is getting his hands on as many as he can.
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I will say I do like the oviform shape of the SmartCarb and also the old PSI BigAir carb, this should work especially well at smaller throttle openings and never understood why the other carb manufacturers did not use it.
Kawasaki used a keyhole shaped carb back in the 70s and there have been several variations over the years. Lots of aftermarketeers have offered offset bore carburetors. Today we have this shape patented and the predictive technique used to design it. PSI actually was infringing on our patents a year after they saw an SC at the hillclimb in Jackson. So as gentlemen we offered Bruce Kahlhammer a licensing arrangement to continue selling the V shaped venturi they had started using, (not the early D shaped big air they have patents for) however after some rude discourse we ultimately had to serve them with a cease and desist order. Turns out the design they had didn't work all that well and they weren't selling enough to really matter. You'll note they had large scallops cut into the venturi to diminish laminar flow and frankly were going in the wrong direction. I'm not sure they are even still in business, which is too bad, they had some pretty cool stuff at one time.
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Wobbly posts on many forums but the forum I refrenced from is a private engine builder forum. I will try to gather his latest thoughts since this was made in August 2014
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Wobbly posts on many forums but the forum I refrenced from is a private engine builder forum. I will try to gather his latest thoughts since this was made in August 2014
I'll call him. Appreciate your making reference to it and interested to see what he was thinking.
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Wobbly's a sharp guy and hard headed, it would not surprise me if he did not drill yor carb and put a power jet in it.
He use the same trick some of the factories use by switching off the electric power jet in the overrev to build heat in the pipe for more rpms
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Wobbly's a sharp guy and hard headed, it would not surprise me if he did not drill yor carb and put a power jet in it.
He use the same trick some of the factories use by switching off the electric power jet in the overrev to build heat in the pipe for more rpms
Oh for sure, he's pissed at me because I couldn't deliver a bunch of carbs to him. I made reference to TSS and the experience was similar and holy hell the romance was over. So he may have out of spite. Ha! No he's brilliant, but I'm thinking he's not the first if he's tried. Had a couple blokes from New South Wales call in to order a bunch of new parts for 3 billet 38s they had fixed....
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Fixed, haha!
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Haha yeah don't bring up the TSS word lol
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I'll side track the topic a bit, sorry. All of my Mod sled motors make peak HP over 500+ rpm sweep just like mod ATV motors. Plus they are .30 hp per cc. A CVT can't just start at peak HP. Most start at 4500 ~ 5000 RPM then end at 9800 ~ 10,000 RPM. To tune a CVT and WIN takes alot more work then you think. I wouldn't use the word easier in any part of it. Your 60' time is everything and if your waiting to make power, you wont win. IMO it takes running 1.1's in 60' and a peaky motor wont turn that time
The smartest guy on a sled team is often the clutch guy. :stung: or should I say if he gets the set up right he can be the hero or if he gets the set up wrong the whole team is a zero
In any winning effort it takes the best of the best of everything. Best rider, best engine guy, best clutch guy and best chassis guy.
The point I was attempting to make in an earlier post was: A CVT has more ability to keep an engine close to the power peak while a package with a multi-gear transmission must have a high power average over the RPM range that the transmission ratios define. To get equal acceleration for two vehicles of equal weight the CVT can do it with a narrower spread of power than the other vehicle with a manual transmission. I takes a less effort for me to develope a two stroke engine package with a power peak that spans 500 RPM than it does to build an engine package that has a peak span greater than 500 RPM.
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Haha yeah don't bring up the TSS word lol
Well it's all about suppliers right? Same BS we go through every day, we can do your work-meet your tolerances etc. End of the day...no.
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Kawasaki used a keyhole shaped carb back in the 70s and there have been several variations over the years. Lots of aftermarketeers have offered offset bore carburetors. Today we have this shape patented and the predictive technique used to design it. PSI actually was infringing on our patents a year after they saw an SC at the hillclimb in Jackson. So as gentlemen we offered Bruce Kahlhammer a licensing arrangement to continue selling the V shaped venturi they had started using, (not the early D shaped big air they have patents for) however after some rude discourse we ultimately had to serve them with a cease and desist order. Turns out the design they had didn't work all that well and they weren't selling enough to really matter. You'll note they had large scallops cut into the venturi to diminish laminar flow and frankly were going in the wrong direction. I'm not sure they are even still in business, which is too bad, they had some pretty cool stuff at one time.
Bruce did spin out back then. Went through a divorce, then a group remade Scorpion brand snowmobiles and ordered ALL the production motors from Bruce and didn't pay or went belly up. Sad deal. Last I knew he out in Utah playing with mountain sled heads.
Odd thing about patents, they don't stop anyone from using it. It just gives you the right to take them to court and fight
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Bruce did spin out back then. Went through a divorce, then a group remade Scorpion brand snowmobiles and ordered ALL the production motors from Bruce and didn't pay or went belly up. Sad deal. Last I knew he out in Utah playing with mountain sled heads.
Odd thing about patents, they don't stop anyone from using it. It just gives you the right to take them to court and fight
It's all true unfortunately and a shame.
Scorpion never had a chance though. Can you say Cannondale? Too much too soon, the Genesis engines were a work of art though and I had an 890 that is still racing today. PSI is in a small building near Ogden Utah. I didn't want to fight with Bruce, as I highly respect the man and knew of him when he worked for Aaen, we were hoping they would just play ball and we all sell better carburetors. Understandably I think he is pretty embittered by his loss, you may recall they had just built a huge facility in Wild Rose Wisconsin before it all went down.
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................Odd thing about patents, they don't stop anyone from using it. It just gives you the right to take them to court and fight
Some other things most people do not understand about patents and the patent process is:
A patent is not a guarantee that the idea or device that is patented functions as the unique features claims in the abstract. The patent office does not test the ideas or device during the patent search or during the patenting process. If a patent is granted it gives the patent holder the legal right to stop someone else that may reproduce the idea or device for financial gain.
Sometimes an original patent holder has a device that works really well but does not know how or why (scientific process involved or the appropriate way to use the device) the device worked. Due to the claims made in the abstract (why it works or how to use it) some one else can be granted a patent on an identical device if the new patent holder can prove that it can be used in a 15% different way or prove the claims made in the original patent were not accurate.
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Furthermore this was also the cause of the intermittent flooding issues that you were dealing with prior to the seizure. After your rebuild and necessary clearancing of the manifold I would also inspect your SC to see if any damage has occured the the fuel inlet needle/seat.
The flange of the SC was touching the RAD valve from 6 to 10 o'clock as marked in black sharpie in the picture. There is a sharp burr there where the aluminum was push back into the SC bore.
(http://i57.tinypic.com/apleb.jpg)
Are you saying I should pull the Allen bolt that holds the needle/seat in there to look at it or just check for flooding before hooking the carb the the motor?
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The flange of the SC was touching the RAD valve from 6 to 10 o'clock as marked in black sharpie in the picture. There is a sharp burr there where the aluminum was push back into the SC bore.
(http://i57.tinypic.com/apleb.jpg)
Are you saying I should pull the Allen bolt that holds the needle/seat in there to look at it or just check for flooding before hooking the carb the the motor?
Who taught you those incredible sharpie skills, Tony? :excitement:
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The flange of the SC was touching the RAD valve from 6 to 10 o'clock as marked in black sharpie in the picture. There is a sharp burr there where the aluminum was push back into the SC bore.
Are you saying I should pull the Allen bolt that holds the needle/seat in there to look at it or just check for flooding before hooking the carb the the motor?
Easier to just gently pull the wire bail from around the needle and slip the needle out. Look carefully with a magnifying glass at the tapered end of the needle for a heavy ring where the needle has been seating/impacting the seat, then check the spring plunger on the top of the needle for return tension. If all good, take a pen light and look down into the brass seat, the edge leading into the inlet where the needle rests should be reasonably sharp without a large chamfer, look for rotational type impacting or hard wearing. There should be little to no ring on the needle, brass smearing or galling down in the seat. If there is I would recommend replacing it. The frequency being transfered into the little parts and pieces at 8-9000 rpm is severe.
And of course cut and file the burr out of the venturi, then I would flat sand the end of the venturi, even at the angle it is worn, won't hurt it. You can do this on a piece of plate glass and a sheet of 220 grit sandpaper.
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The needle/seat was damaged so I put the new 40mm SC in and rode for an hour to break in new piston and rings. After refueling I was going to try some small hills. Got stuck 3/4 of the way up and had to go back to the bottom. Tried again but when I got to the same spot/soft sand the rings were siezed. I am guesiing this piston needed a little more break in time. Plug was fine and seemed rich enough. Whats it look like?
(http://i60.tinypic.com/15n4phx.jpg)
(http://i57.tinypic.com/2505pjo.jpg)
Smartcarb suggested going with a slightly richer metering rod.
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Tony, the 2nd smartcarb came with too lean of a needle for that engine setup due to an error by Tom not recording information about this engine being heavily modified from stock, right? It normally would have come with a richer needle if he had recorded the correct information, right?
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Tony, the 2nd smartcarb came with too lean of a needle for that engine setup due to an error by Tom not recording information about this engine being heavily modified from stock, right? It normally would have come with a richer needle if he had recorded the correct information, right?
Yes, Corey went back to the build sheet and could see no reason why I would need a richer metering rod. Apparently Tom does not consider a 431cc 2 stroke a modded motor. The build sheet has a place for mods to consider when building a carb for it. I would guess the whole big bore thing is overlooked. After reading the thread Corey said the carb would have shipped with a richer metering rod if he had known what motor I was running. All he sees is 250r on the build sheet.
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LOL. Yes, I do believe a 431 big bore would be count as a "mod" for a 250r. I think that qualifies.
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rode for an hour I am guesiing this piston needed a little more break in time. .
thats about 55min more than you needed. most likely your a/f ratio still isnt right. never assume your piston clearance is correct either. regardless who assembles it. always double check for yourself.
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thats about 55min more than you needed. most likely your a/f ratio still isnt right.
That's the general consensus. I have lots of clearance now that the molten aluminum has been sanded off the rings. :lol:
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you might have to take the bike to someone with equipment that can check a/f ratios through the full throttle range. i dont really see any other way to get it sorted out.
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Tony, the 2nd smartcarb came with too lean of a needle for that engine setup due to an error by Tom not recording information about this engine being heavily modified from stock, right? It normally would have come with a richer needle if he had recorded the correct information, right?
OK let's do a little review so we can all understand what is happening here and avoid any more costly mistakes. Tony was given a loaner carb to try, after installing it had a sticky float issue. He started calling our tech service line, where he was advised how to handle the float issue and some basic tuning tips. From there a persistent mid range stumble showed up and we started chasing things around to determine the cause. My guess is our service technician was guiding him through proper float bowl settings thinking we had a capacity or fill rate issue. None of that worked so we likely went on to metering rod selection and started stepping up richer. All this by the way working with a non alpha customer using a borrowed SC and supplying parts to help Tony get his modified engine dialed. We love you guys. Anyway it was finally discovered that the carburetor was indeed hard rubbing (inside the intake boot) and likely the issue all along. Some pictures were posted and the plug showed a nice light tan and apparently at or near a perfect burn which we are all used to seeing with an SC. The piston on the other hand is not happy at all and shows localized over-heating, yielding of the exhaust edge and chunking off.
It's clear the carb touching the intake caused the fuel to turn to a highly aerated froth along some frequency (mid range) causing the carburetor to deliver pre-aerated mixture to the engine at those points and burned the piston. Alright, in the meantime another carburetor is ordered but nothing I have is specifying this is going onto this same engine we spent a couple months trying to dial in and had a reasonable expectation of what metering rod it should come with. This is clearly our fault for not requesting enough information. Notwithstanding on the other end, had I the earlier carburetor and several metering rod variants in my hand, a brand new bored, ported custom engine needing broken in and several months of plug readings. Intuition would have led me to the richest rod I had already been running. I am reasonably certain from looking at your plug the .074 MR is very close to what you will need with this engine. The .080 MR, which is our standard issue for 300 class stock to lightly modified dirt bikes will not work and your piston has brought that to your attention. When we receive your original carb back we can validate these things and make sure we are correct. The new 40 SC you have will require the richer rod for best performance and to protect your engine. Sand of course is the hardest loads there are and any engine will want more fuel under these conditions.
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OK let's do a little review so we can all understand what is happening here and avoid any more costly mistakes.
Yep, that is a good summarization. Thanks Corey for your help. I was beginning to have fears of ever getting this thing going correctly when I had to pull start the bike. Got the .074 MR in and idle set last night. Hope to head to the dunes today to break the piston in. Ha ha, even started 2nd kick after getting the rings unstuck! That was surprising.
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Cory when will the next round of cast carbs be available ?
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Cory when will the next round of cast carbs be available ?
Tim, you might have to PM him on that one. Just thinking out loud. All went great with the SC today. If the MR is rich I really did not notice it. The carb works great down low where we were all having problems. I really need to get the shearer inframe puma pipe on this bike. Thats my next mod. The frame is cracked and I have the new one waiting for a frame swap.
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Tim, you might have to PM him on that one. Just thinking out loud. All went great with the SC today. If the MR is rich I really did not notice it. The carb works great down low where we were all having problems. I really need to get the shearer inframe puma pipe on this bike. Thats my next mod. The frame is cracked and I have the new one waiting for a frame swap.
Ok will do !
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Cory when will the next round of cast carbs be available ?
Tim, I have been waiting to answer hoping to give my best information. We have solicited numerous vendors and have narrowed down the quotes and will selecting a new casting vendor in the next few days. Trusting the result will be higher quality castings in much higher volumes. We will resume cast SmartCarb production within six weeks of the selected shop taking our work. The process involves checking the quality and this time creating tooling for the 36 and 40mm sizes in addition to the existing 38 mm castings. We will announce our expanded production as soon as it begins, including a release date for the 36 & 40 mm sizes.
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Thank you . I have a 38 cast that I have very pleased with. I plan to get another.
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We will announce our expanded production as soon as it begins, including a release date for the 36 & 40 mm sizes.
We will be patiently waiting. I would like 2 more 40mm.