TRX250R.ORG
Workshop => Carburetor, Intake, and Exhaust => Topic started by: PorP on August 08, 2020, 08:36:27 PM
-
Folks, new here. To summarize, Tony Kellner (Barry hawks mechanic) was my mechanic when I raced gnc /gncc on 450rs. I also had a 250r at this time and bought one of the 86 ported cylinders he had left over from hawk to run on my 87 250 with spacer for 265 cc's of monster power. That lasted 2 hours before the counter balance bearings went out and broke a case. That was 2010. The quad sat as is without motor until this past month [fuel was drained from tank and carb).
2 months ago I bought the case i needed, all new bearings and seals for motor including water pump, new stater, coil, countenance, cdi, professionally rebuilt crank with hot rod and more. I rebuilt the entire motor, put that same rust-free top end on it and inspected the carb to make sure there was no gumming.
The thing started in 3 kicks, had a fuel leak from the petcock and it rev'ed high with no throttle which I pulled the kill. I fixed the petcock and adjusted the slide to where I can hear it hit the bottom of the carb like I would on my 450r's.
Today now the tank is fixed, i start it in 3 kicks. Take it for 1/4 mile down the road and back..... it won't rev out, doesn't seem right at anything past an 1/8th throttle (always feels like the choke is on) . I change the cdi to make sure but it won't start cause the plug is so fouled. Put a new plug with the oem cdi and it is smoking like a chimney from the exhaust, blueish. Went back to the plug an hour later, all the foul was completely dry, didn't have the glisten of tyranny oil.
I'm running amsoil interceptor about 45:1, a PJ36 carb which is the same as i raced with for the PJ haters. Same jetting as when she dropped the counter balance.
I've got a good 4k sunk into this rebuild, which is already a full leager/pep 250r. Before I sink more I am hoping this forum can help.
I am an avid mechanic, I am not a pro.
That said,
I read right side crank seal can cause this, the seal is definitely not damaged, can i have pounded it to far in? Is not touching the bearing though?
Could it be the o rings in the carb dried up like they did in the petcock? Note the carb is not leaking.
Did I drop the slide to far down?
Possibly something else?
-
Welcome to the forum bud.
First thing I would do is a leak down test. That test will tell you if either crank seal is bad or if you have any air leaks in your engine. Then after that I would check your reeds, and all the ignition system . Download the manual off this site if you don't already have one.
Good luck with the resurrection!
Loren
-
Sounds like air issue or a rich issue. Reeds good? Air filter clean? Air box lid on? What jetting you running now?
-
Thank you for the replies.
It is definitely rich, fouled the plug in 1/2 mile on the road. I checked the reeds while reassembling, they are good. Entire ignition is new, I verified all components provided proper resistance per the shop manual.
I do not have a leak down tester. I'm going to pull the carb today but didn't change jetting from when it was running good.
-
also, I run a twin air with no lid, a full LRD adjustable exhaust.
One note i found odd, when i did the compression test the first time I got 155psi but forgot to hold WOT, I did it again WOT and got the same reading. I know 155 is not great and have rings on order but 155 should be plenty to run well.
-
So wet fouling the plug tells me that you are too rich, but you were running this exact jetting before so that is odd. The compression is way low for sure. I built my leak tester from pvc and a gas test fitting all from home depot. Then I used a plug for the exhaust. I think I have $25 in it.
I wonder if maybe your float needs adjusted? I would have to check the manual for verification, but I believe it is 16mm from the carb body to the mold line in the float. You could be filling the carb with gas and it's getting into the cylinder.
Loren
-
It's running rich, but why. Is it getting too much fuel? Not enough air? Something else is being burned with mix, like trans oil. Something blocking the exhaust. Poor combustion, poor spark.
155 psi on a race motor is low. Is your gauge good? The Schader valve and orings can go bad. If you gauge is good, you might have found your issue. poor compression will cause a poor burn.
I also highly suggest having/building a top end leak detector kit. They can be built pretty cheap and are a super useful tool to have.
Side note, is Kellner still around? Haven't heard anything about him since the hawk days.
-
16mm float level is correct but make sure you don't have the spring depressed in the spring loaded needle when you check the level.
-
I will make a leak tester....
I was just getting ready to check float height and then I broke the choke of in the carb when I was removing the bowl screws.... having a splendid weekend so far.
There is something definitely wrong with the floats though, they are sagging 24 or 25mm, way out of spec.
I run tame prox piston (9:1 if I remember right) and stock head in it, I don't like messing with race gas because I like going to hatfield mccoy. I think 155psi is in spec for stock, correct? Thought the manual said 170 +/- 15. All that said, am I really that far out at 155?
-
2ndmoto,
I'm not sure on Kellner, maybe 2011 was the last time I used him? Andy Lagzdins and I became good buddies, his shop was in Baltimore (a lot closer for me) so I started using Andy when I needed help, until he closed up shop and moved to cali.
-
If you were jetted for a hi compression motor before and now have changed to low compression you will need to rejet.
-
Top end, piston, exhaust, airbox/ filter and jetting are all the same exact parts from the last time it was running good.
The only thing changed is the spacer plate, I didn't port match it cause I got too excited but I can't imagine that would cause an issue this big.
-
How thick is the spacer? Should be .190" if your just running an 85-86 piston on your long rod crank. A healthy fresh engine with a stock TRX head gasket will normally be 180psi +/-. Same exact engine with an ATC head gasket will be 200psi +/-. Both mine are 205psi with stock cylinders, wiseco 66.75mm pistons, 86 heads & ATC head gaskets. One is all 86 & the other is an 86 bottom with 89 cylinder & hotrods lr crank.
-
I would get the carburetor sorted out then see what happens.
-
How thick is the spacer? Should be .190" if your just running an 85-86 piston on your long rod crank. A healthy fresh engine with a stock TRX head gasket will normally be 180psi +/-. Same exact engine with an ATC head gasket will be 200psi +/-. Both mine are 205psi with stock cylinders, wiseco 66.75mm pistons, 86 heads & ATC head gaskets. One is all 86 & the other is an 86 bottom with 89 cylinder & hotrods lr crank.
It is 5 mil, 4.87 on my calipers and a trx gasket
I've not heard of the atc gasket thing? Do you run 93 octane with that much psi?
At best if 180, I wouldn't expect 155 to make it so the bike sputters all the time and won't rev out, not optimal performance but I would still expect some perform. Am I wrong?
-
I would get the carburetor sorted out then see what happens.
Funny you say that, the pin was 1/2 way out of the float, that's why it looked so weird.
It's all apart now including the choke I broke this morning.
It's got 50 pilot, needle is 2nd slot from the bottom and the main is 168.
-
Both mine are on straight race gas but I could get away with 50/50 mix race/non-eth super.
-
Both mine are on straight race gas but I could get away with 50/50 mix race/non-eth super.
You had my attention for a minute. Race gas isn't readily available at hayfield mccoy, I gotta be able to run super at most.
And the way hayfield is set up with the ability to ride paved road into town, the truck (or hotel) is start and end, you get gas and food in the different towns the trails take you to.
-
Shoot I'm running 48/178 on my son's mildly ported cylinders with the needle in the middle.
Loren
-
I must have not messed with the needle before....
Ps, when i was in the slide, i found 2 clips on the needle, i don't know if this is a common pj thing, i never heard of it.
Between that, the floats and the broken choke, i just bought a 38mm air striker. It's supposed to be here Friday so I will update next weekend....
-
Shoot I'm running 48/178 on my son's mildly ported cylinders with the needle in the middle.
Loren
What altitude (out where do you live), Loren? I can explain the pilot I think? A lot of racers ran rich on the pilot to prevent detonation. A lot of racing is WOT and no throttle and on the binders. Being rich in pilot helps lube the cylinder when you have a hand full of clutch and a foot full of brake.
On the 168? Can't explain? It was 10 years ago... so with a grain of salt.... i feel like I must have done a 4th gear plug chop? It would be abnormal for me to not chop the main.
-
Oops sorry I forgot to mention my elevation and I didn't notice where you are riding. We ride from sea level to around 3,500 feet. I understand the big pilot for sure. I have had a few MX two stroke dirtbikes and they always have a rich pilot circuit. Which is not the best for trail riding in my experience. But for MX racing it makes sense like you said you don't want detonation!
Loren
-
Oops sorry I forgot to mention my elevation and I didn't notice where you are riding. We ride from sea level to around 3,500 feet. I understand the big pilot for sure. I have had a few MX two stroke dirtbikes and they always have a rich pilot circuit. Which is not the best for trail riding in my experience. But for MX racing it makes sense like you said you don't want detonation!
Loren
Thanks for the reply Loren!
Now that I had some time to think on it, the other thing that makes jetting so complicated are riding types, when i do go to hatfield, my dad rides a ute so I almost never see the main in 5th or 6th.... when i race, I'm mainly 2nd, 3rd and maybe some in 4th. If you plug chopped in 5th or 6th... (or if i did) I'd probably end up leaner on the needle and richer on the main.
-
Oops sorry I forgot to mention my elevation and I didn't notice where you are riding. We ride from sea level to around 3,500 feet. I understand the big pilot for sure. I have had a few MX two stroke dirtbikes and they always have a rich pilot circuit. Which is not the best for trail riding in my experience. But for MX racing it makes sense like you said you don't want detonation!
Loren
Thanks for the reply Loren!
Now that I had some time to think on it, the other thing that makes jetting so complicated are riding types, when i do go to hatfield, my dad rides a ute so I almost never see the main in 5th or 6th.... when i race, I'm mainly 2nd, 3rd and maybe some in 4th. If you plug chopped in 5th or 6th... (or if i did) I'd probably end up leaner on the needle and richer on the main.
You are missing or misunderstanding a very important and basic fact about carburetor tuning. The engine and the carburetor does not know what gear you have selected while you are riding. Anytime the throttle position is in the range of approximately 3/4 to wide open, the main jet is the circuit that is metering the majority of the fuel flow into the engine at that instant. When you position the throttle wide open in any gear the main jet is being used. A carburetor is throttle position sensitive not transmission gear sensitive.
My most common error I find when tuning Keihin carburetors for customers is: They have too large of a pilot and the diameter of the straight portion of the needle is too large and or the slide cutaway is too lean. This error in carburetor tuning theory or lack of a large needle and or slide selection causes them to keep increasing the pilot jet size to take the lean bog or hesitation when suddenly opening the throttle from an idle. This error in theory by oversizing the pilot will overlap into the throttle positions where the slide cut a way and straight diameter portion of the needle should be controlling the fuel flow at less than about 1/2 throttle position.
Moving the clip on the needle cannot affect the fuel metering until the tapered portion of the needle is changing the fuel flow area between the needle jet and the needle. On most Keihin carburetors, on two strokes, the start of the taper is not exposed until about 1/2 throttle opening.
Another common problem guys have when recommending jetting specs. on Keihin carbs with buddies that have similar engine packages is: The needle jets and needles are made of brass/bronze and they ware rapidly. This ware causes the need to use a different needle to get identical fuel metering. I wish Keihin aftermarket needles used the hard anodized aluminum needles like they supply to the OEMs for their CRs, YZs, etc. It has been my experience that using similar metals for the needle and needle jet or in any design of parts that contact each other is a common engineering error of freshman engineers or intentionally controlled by the marketing departments to limit the life of their products.
-
Jerry,
I think i understand (didn't know the needle part) i'm aware the atv doesn't care which gear.
But what I think i also understand (or maybe not? ) is rpm and time. Because this is not a sealed environment, i believe venturi effect is impacted by piston speed. To say i believe venturi is maximum at max rpm. And the time piece is that window of max venturi effect in 4th gear is pretty short.
-
Installed the air striker with 50 pilot, 175 main, needle 3rd clip and floats adjusted. Same problem.
So other things I think might cause this.
I installed a dynatehc cdi, it sparks during the kick. Oem cdi sparks after the kick is done, like .25 or .5 seconds after the kick is finished. Oem spark is louder and shaper, but it won't start on this cdi.
When i dropped the counter balance bearings, it broke the CB holder. I replaced it with a boss racing adjustable timing holder. I got no instructions, so I set it to 0 degrees advance assuming that it correct.
Do I need to advance the timing and run the oem box?
-
I installed a dynatehc cdi, it sparks during the kick. Oem cdi sparks after the kick is done, like .25 or .5 seconds after the kick is finished. Oem spark is louder and shaper, but it won't start on this cdi.
Do I need to advance the timing and run the oem box?
I have had a lot of problems with the Dyna tech CDI boxes. They typically act like the main jet is too rich. I have also had a few OEM CDI boxes act real rich and will kick back real hard when kick starting. The Honda CDI boxes that kick back real hard have a timing curve malfunction and have the ignition firing around 45 to 50 deg before TDC.
Have you removed the ignition flywheel and checked for a sheared flywheel wood riff key?
You should not need to advance the timing if the wood riff key and OEM CDI box are good.
-
0 degrees should be fine. Something is up with your cdi, I recall mine pulling spark through the kick. Would be nice if you could get your hands on a known good one.
Let's start checking things off the list. Did you do a leak down test? Grounds are good? Low resistance between points? Check the spark plug cap and coil.
-
Jerry,
I think i understand (didn't know the needle part) i'm aware the atv doesn't care which gear.
But what I think i also understand (or maybe not? ) is rpm and time. Because this is not a sealed environment, i believe venturi effect is impacted by piston speed. To say i believe venturi is maximum at max rpm. And the time piece is that window of max venturi effect in 4th gear is pretty short.
I am not sure what you mean by venturi effect. Are you saying that the suction of the main jet is at a maximum at the maximum RPM? If so, the suction or what many guys call the signal strength, is at a maximum when the air speed flowing over the needle jet shroud is at a maximum.
The maximum velocity over the needle jet shroud is a function of where the torque and power peak occur. Maximum air flow through the carburetor usually occurs very near the torque peak. On narrow power band two strokes, the torque and power peaks most often occur at about the same RPM, so signal strength is at a maximum at the power peak. On a 250 cc single cylinder two stroke that is designed to produce maximum acceleration, the torque peak will often occur 1000 RPM or more before the power peak. Air flow at maximum RPM (in the over rev RPM range) is seldom very high because the engine is loosing torque and power rapidly after peak power occurs.
-
Jerry,
Ya the engine is a complete rebuild including the crank, woodruff key is installed. My problem is primarily on the main, it seems to idle fine. I've read what you said on the dynatech cdi, the oem vdi issue is new to me though.
Ya, venturi is the air flowing from large opening to a small opening and then to a larger than small opening, it creates the vacuum on the jets.
-
0 degrees should be fine. Something is up with your cdi, I recall mine pulling spark through the kick. Would be nice if you could get your hands on a known good one.
Let's start checking things off the list. Did you do a leak down test? Grounds are good? Low resistance between points? Check the spark plug cap and coil.
I was out of town this week until Friday and didn't build the tester yet.
I had a no spark issue for a week that ended up being a bent pin in a plug, because of that everything electrical has been resistance checked and checked good in accordance with the shop man.
-
p.s. Jerry,
You described what I'm seeing on both cdi boxes including the oem box which I think is sparking real late, there is a lot of kick back on it. It's almost as a capacitor (or something) is going bad and not passing the signal right away to the coil. I'm assuming your comments on oem boxes are older boxes that have gone bad? If so, that's my case.
Any recommendation here for cdi boxes? I only bought the dyna tech because I couldn't find new oem and it was the more expensive option (I wrongly assumed cost = quality).
-
Jerry,
Ya the engine is a complete rebuild including the crank, woodruff key is installed. My problem is primarily on the main, it seems to idle fine. I've read what you said on the dynatech cdi, the oem vdi issue is new to me though.
Ya, venturi is the air flowing from large opening to a small opening and then to a larger than small opening, it creates the vacuum on the jets.
Fuel jets will have vacuum on then anytime air is passing over the hole that connects the jet to the airflow passageway through the carburetor. A true venturi is a optimally shaped reducer, placed in the air flow passageway, that is used to raise the velocity where the diameter is at it's minimum. The increase in velocity at the fuel discharge hole, places more vacuum on the jet than it would have without the venturi. Air flow through the carburetor is always reduced even with the best designed venturi.
If you have not removed the flywheel to check for a sheared key I would do it just to eliminate that one possible cause of the timing being severely advanced. The spark being delayed after the engine is coming to a rest is not uncommon. The capacitor in the CDI box was charged on the previous engine revolution, but was slowing down as the piston approaching TDC and the trigger bump on the flywheel is approaching the pickup. The crankshaft may not have had enough momentum to make the leading and trailing edge of the trigger bump completely pass by the pickup coil. The crankshaft rotates enough to pass the leading edge of the trigger bump and then the compression slowly pushes the crankshaft backwards so that the leading edge of the trigger bump passes the pickup again triggering the spark. The spark is normally triggered when the trailing edge of the trigger bump passes by the pickup.
If the flywheel key is good, borrow a CDI box off of a good running bike and see if it rums correctly.
-
I'm sure someone on this site can ship you a known working OEM CDI so you can test that.
-
I'm sure someone on this site can ship you a known working OEM CDI so you can test that.
That would be awesome.... willing to pay all shipping and rent.
-
I stripped the cylinder off it today, no oil in the base. Just anti freeze (cylinder still had some in it after i drained) and a little gas mix, just enough to smell.
I think the base is sealed good.
I did have a little gas mix on the gakets to the intake and base gasket.... not sure if that's normal.... i think maybe running this rich?
I found 2 more cylinders for it though while I was rummaging through parts... i found a heavily ported and bored pro works 88 cylinder and a what I think could be an untouched 85 cylinder with original paint, sleeve, no porting and the original inspectors mark in the intake. Pretty excited about that later one.
Also found a stache of old race parts i had, asv levers, quick release tank fittings, sparks full exhausts, lots of other stuff and a complete sparks 485r (450r bored) motor. That motor has one of John Natalie's sparks heads on it from his championship 2005 year. I forgot I had it and it ended up being too much to race with.
Sorry about all that... got excited I found so many memories.
-
Nice to find old parts. Sounds like you have a good stash.
You are narrowing down possible issues. Seems like it is pointing towards ignition
-
Nice to find old parts. Sounds like you have a good stash.
You are narrowing down possible issues. Seems like it is pointing towards ignition
I think so, I just popped the flywheel like Jerry said to make sure the key wasn't broken or I didn't goon-up when I installed it. Everything was fine.
CDI is the only thing left that I can think of.
-
Also, on another note... and probably wrong section but I already got this one going.
I'm want to replace the piston, my calipers are telling me 67.75mm ish. Is this a 68mm?
And also, just noticed my rear shock bumper dry rotted, is there some you recommend for rebuild? I haven't had shocks built/ rebuilt since Laz passed away, looking for someone as reputable.
-
Pistons typically go by .010" bore sizes. .010" = 0.25mm. so it is a 67.75mm piston
-
I have been out of there suspension side of things for a while. Norm had a guy do a rebuild for him recently. I have not heard the race report on it. Check out Derisi Racing. I dealt with Santo many years ago and he was a stand up guy
-
I have been out of there suspension side of things for a while. Norm had a guy do a rebuild for him recently. I have not heard the race report on it. Check out Derisi Racing. I dealt with Santo many years ago and he was a stand up guy
Right, I totally forgot about Santo.
And thanks on the piston. I did a quick search and couldn't find one. I'll be more dedicated now that I know what I need.
-
Update, I cannot find a 67.75mm piston. Prox and wiesco do not make them.
Is this a "some' year cr piston?
-
They might have phased out the .010" bore sizes. You can still find rings for the 67.75, but it doesn't look like piston kits are available
-
They might have phased out the .010" bore sizes. You can still find rings for the 67.75, but it doesn't look like piston kits are available
That piston is garbage. Top ring broke and overlapped in the same ring groove. Also looks like the top of the piston was starting to melt.
Thanks 2ndmoto.i wasted your time, apologies. I cleaned the top of the piston and found the part #. It's a 68mm wiesco.
Maybe I should have paid more than $50 for digital calipers?
-
Pistons typically go by .010" bore sizes. .010" = 0.25mm. so it is a 67.75mm piston
Measure the bore. If the piston measures 67.75 it is probably a worn out 68.0 mm piston. The piston's largest diameter is usually the bore size minus the piston to cylinder wall clearance. If the bore size is 67.75 the piston's largest diameter should be around 67.65 to 67.70mm
-
Pistons typically go by .010" bore sizes. .010" = 0.25mm. so it is a 67.75mm piston
Measure the bore. If the piston measures 67.75 it is probably a worn out 68.0 mm piston. The piston's largest diameter is usually the bore size minus the piston to cylinder wall clearance. If the bore size is 67.75 the piston's largest diameter should be around 67.65 to 67.70mm
Thanks Jerry. The part# verified it's 68mm. I did measure the bore.... on my calipers it was coming up 67.85-67.9.
I then measured a brand new 66mm piston at 65.75.
My calipers just seem to be .25mm off at the bigger measurements despite being zeroized.
-
Glad you found it
-
Well, I'm making 185-190psi on this new top end. Waiting on the new cdi now. Hopefully that fixes it.
Otherwise can I use a cr cdi with the trx flywheel and stator?
-
Have to run cr stator and flywheel. Also need a stator plate
-
Hey folks, I haven't touched my R in a year due to life changes.
But I got a leak down tested, Found it was leaking from the rear cylinder base bolt threads on the left side. Leaking as fast as I can put air in. I got it in the sunlight and found a crack that runs along the cylinder bolt. I am assuming it is cracked in the inside too.
Question is, can this be repaired with welding? Worried about crank clearance. You guys know as well as me left cases are hard to find so looking for other options.
I do have a pic of the crack but can't remember the hosting service I used.
-
Hey, we all know things happen but welcome back. Take a picture with your phone and store it. Make a reply and then hit the attachments and other options icon. Next choose a file to attach from your photo library.
Joe
-
Billet cases have been recently released if you want to go that route.
Joe
-
You can zoom in, that crack runs to the top. I do not see the crack on the inside but based on how it's leaking, pretty sure there is a crack behind the crank.
-
You can zoom in, that crack runs to the top. I do not see the crack on the inside but based on how it's leaking, pretty sure there is a crack behind the crank.
Joe, I saw that, but they are like 2/3 the cost of a fresh built complete motor. Unless you are talking about a different product?