TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: Bowtie316 on July 01, 2014, 11:22:50 AM
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My buddy had his motor apart so we checked the port timing on it. It's a 310 trx9 port match power valve machined cylinder. Short rod motor, no spacer. The exhaust came out to 187.5 which is about what I would expect, but the transfer was only 120. Actually for the transfers, the entire port(s) were low, as in the bottom of the port was 2mm below the top of the piston. Is this normal? I would think it should be flush with the top of the piston at BDC. Sleeve was perfectly flush with the top of the cylinder and the port matching sleeve to cylinder is fine so the sleeve didn't move.
Does anybody have any ideas?
Would he gain anything with a few more degrees of transfer timing? It runs good now, just maybe a little soft on the bottom and tends to run a bit hot.
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not sure if thats normal because i never seen a esr cylinder but i dont like the idea of trans floors below the piston top and certainly wouldnt intentionally set one up like that. 120 is pretty low. of all the engines ive ever messed with none of them have been that low. 124 i think is the lowest ive ever seen but i have almost no experience with 250r stuff either. if your intention was to raise it 2mm thats quit a bit. you could put something about 2mm under your spacer and check timing then youll know for sure. why the floors are lower than piston is hard to say as theres a number of reasons why it would be like that
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My buddy had his motor apart so we checked the port timing on it. It's a 310 trx9 port match power valve machined cylinder. Short rod motor, no spacer. The exhaust came out to 187.5 which is about what I would expect, but the transfer was only 120. Actually for the transfers, the entire port(s) were low, as in the bottom of the port was 2mm below the top of the piston. Is this normal? I would think it should be flush with the top of the piston at BDC. Sleeve was perfectly flush with the top of the cylinder and the port matching sleeve to cylinder is fine so the sleeve didn't move.
Does anybody have any ideas?
Would he gain anything with a few more degrees of transfer timing? It runs good now, just maybe a little soft on the bottom and tends to run a bit hot.
Does ESR make a sleeve for a about a 4 mm stroker crank?
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maybe thats what they did. used a 4mm sleeve . sounds plausible anyways
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I would expect the port to be taller if it was for a +4 stroke. It's normal size, just lower than I think it should be.
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im not sure dude. call esr and see what they say. floors 2mm lower is alot. something dont sound right about that.
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if the port is 2mm lower than the piston at BDC then more than likely this was setup as a +4 stroked cylinder. When you stroke the crank the crank will travel 2mm lower and and 2mm higher in the bore. Stroking the crank also adds a little more port timing to the exhaust duration and about twice the amount to the transfers duration
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I wish now that I would have measured the port heights and distances from the top of the cylinder. I don't think ESR offers a 310 for the +4 stroke, I know they do for the 330. I might try to get the ports measured and try to get ahold of Eddie. I'll post some pictures up too if I get it back apart.
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was 187 with the valve open ?
lets assume you degreed it correctly. 120 is very low for any type of high performance engine. not what i would expect from a trx9 port. plus the floors are 2mm lower than piston. somethings goofy
i havent degreed my ktm250 but i did trace the ports onto paper and the transfers are damn near the same height as a stock cr500. 72stroke on the ktm and 79 on the cr5. cr5 is 124 trans, if the 72stroke ktm are nearly as high that would put the ktm 128 ? 130 ? i dont know but theyre tall. its a bone stoke mx engine with power valve. your esr 310 should be similar i would think
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was 187 with the valve open ?
lets assume you degreed it correctly. 120 is very low for any type of high performance engine. not what i would expect from a trx9 port. plus the floors are 2mm lower than piston. somethings goofy
i havent degreed my ktm250 but i did trace the ports onto paper and the transfers are damn near the same height as a stock cr500. 72stroke on the ktm and 79 on the cr5. cr5 is 124 trans, if the 72stroke ktm are nearly as high that would put the ktm 128 ? 130 ? i dont know but theyre tall. its a bone stoke mx engine with power valve. your esr 310 should be similar i would think
It's a PV cylinder without the PV option added, it has a plug in it currently, so yeah, basically open.
I agree it seems low, the fact that the bottom of the port is below the top of the piston seems to confirm that it's low. I would have expected around 126°. Does anyone know how many degrees a change of 2mm would be? I would check but the only one I have torn down right now is a +4 mil stroker and would be different.
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I wish now that I would have measured the port heights and distances from the top of the cylinder. I don't think ESR offers a 310 for the +4 stroke, I know they do for the 330. I might try to get the ports measured and try to get ahold of Eddie. I'll post some pictures up too if I get it back apart.
Does the sleeve match the aluminum along the top of the transfer ports? or does it hang down approximately 2 mm below the aluminum port roof?
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Does the sleeve match the aluminum along the top of the transfer ports? or does it hang down approximately 2 mm below the aluminum port roof?
The bottom of the port matched up perfectly. I can't remember if I looked at the top.
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did you talk with esr. wondering what they have to say about it
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ESR said it happens sometimes on these cylinders but that it was nothing to worry about.
It also blows out base gaskets, this is the third time. Surfaces are flat, and the last time we put high-tack on it, it lasted longer but still blew out. Could this be related?
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you said the floor was 2mm below the piston top. did you measure that or just eye ball it and guess ? if a cylinder is setup for a specific stroke, specific piston, specific rod etc etc, its hard to believe it can be 2mm off. not that youll lose 10hp or anything but it sounds like their castings arent very accurate at all. which is pretty sad considering they probly put quit a bit of time into it. then again i have to question how much time was invested after hearing of the coolant issues at the exh side. i think we already discussed this stuff. if your unsure the design will be sufficient, call in some experts to get a second opinion
doubt the base gasket issue has anything to do with your piston not level with the transfer floors. havent had any of mine blow out but bought used bikes with them blown out. generally on every engine i do ill put a few dimples along the thin section around the outside transfer area. 99% of the time i use a sealer also. this is only my way of doing it. you may have to find your own method, thats pretty much what i did. never had a base gasket blow on me. never had one leak either. only time i ever had a gasket problem is when i used some junk material from the hardware store on the reed block and it leeked. learned my lesson. after that day oem gaskets is the only thing ill use unless its a specially project and the cylinder needs to be at a certain height then ill either stack honda gaskets or use klingersil at what ever thickness i need
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you said the floor was 2mm below the piston top. did you measure that or just eye ball it and guess ? if a cylinder is setup for a specific stroke, specific piston, specific rod etc etc, its hard to believe it can be 2mm off. not that youll lose 10hp or anything but it sounds like their castings arent very accurate at all. which is pretty sad considering they probly put quit a bit of time into it. then again i have to question how much time was invested after hearing of the coolant issues at the exh side. i think we already discussed this stuff. if your unsure the design will be sufficient, call in some experts to get a second opinion
doubt the base gasket issue has anything to do with your piston not level with the transfer floors. havent had any of mine blow out but bought used bikes with them blown out. generally on every engine i do ill put a few dimples along the thin section around the outside transfer area. 99% of the time i use a sealer also. this is only my way of doing it. you may have to find your own method, thats pretty much what i did. never had a base gasket blow on me. never had one leak either. only time i ever had a gasket problem is when i used some junk material from the hardware store on the reed block and it leeked. learned my lesson. after that day oem gaskets is the only thing ill use unless its a specially project and the cylinder needs to be at a certain height then ill either stack honda gaskets or use klingersil at what ever thickness i need
No we didn't measure the 2mm, it's just what it looked like. And with the transfer timing low it seemed about right.
Eddie suggested the use of an oem gasket, said they were better than what he sent. I was just curious if low transfer timing could cause excess crankcase pressure pushing the gaskets out.
Thanks for the idea of dimpling the surface, that should help.
As for the porting, I think he is going to send it off to another builder to have a look and raise the transfer ports up where they should be.
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2mm is alot. .080" approx. maybe it just looks like 2mm but really its much smaller ? either way, if the cylinder was designed for your stroke,rod,piston then theres no reason the window floor shouldnt be even or very close to even with the piston top. depending whats going on with the rest of the cylinder , stacking some gaskets in conjunction with porting might be a good option. who ever you send it to should be able to get it sorted out if they know what theyre doing
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It was a lot, going my memory it was around half the thickness of the sleeve. And the transfer port timing was low by the same distance, like the entire transfer slid down. He will have it apart again for new gaskets, I will try to post some pictures and get good measurements.
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We got it apart last night and measured, the lowest drop was 2.18mm and the largest drop was 2.54mm. This is measuring from the top of the piston at BDC to the bottom of the transfer ports. It's hard to get a good picture but the exhaust port is the same way.
(http://i851.photobucket.com/albums/ab73/bowtie316/20140919_190013_zps8df2e16c.jpg) (http://s851.photobucket.com/user/bowtie316/media/20140919_190013_zps8df2e16c.jpg.html)
(http://i851.photobucket.com/albums/ab73/bowtie316/20140919_190103_zpsa84dac3a.jpg) (http://s851.photobucket.com/user/bowtie316/media/20140919_190103_zpsa84dac3a.jpg.html)
Eddie said this was normal and not a problem. While it may be normal to him, it doesn't seem right to me, I think at the minimum we should get the port roof up where it's supposed to be.
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The most important thing when setting up the cylinder is to make sure the exhaust port and transfer open at the correct time.
when you add a + 4 stroked crank the cylinder will gain a bunch transfer port duration. You don't just slap a 2mm spacer under the cylinder like everyone thinks.
You need to put a degree wheel on it and come up with your port timing durations to determine if the porting is correct.
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The most important thing when setting up the cylinder is to make sure the exhaust port and transfer open at the correct time.
when you add a + 4 stroked crank the cylinder will gain a bunch transfer port duration. You don't just slap a 2mm spacer under the cylinder like everyone thinks.
You need to put a degree wheel on it and come up with your port timing durations to determine if the porting is correct.
I did, see the first post, exhaust was 187.5 and transfers were 120. The 120 kind of backs up our thoughts on the port being low.
And I certainly don't plan on cutting it 2mm blind, the plan was to degree it to maybe 125 or 126, scribe a line, and send it to somebody with the tooling to do a proper job.
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if you add a 1mm you will be around 124.5 and 190exh, i dont think you want to raise it anymore
Otherwise send it out to a shop to be ported to the specs you want for your application
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somebody probly already mentioned it but i think what you have is for a +4 crankshaft. perhaps esr uses that cylinder for the standard stroke and the +4 to kill 2 birds with one stone. if using it on the standard stroke like your doing, if probly requires a different dome than the +4 that sits 2mm lower so the squish clearance is in the normal range.
if your using a +4 cylinder with a standard stroke crank then yes it would be normal to see the floors sitting low. but if the cylinder was originally intended for a standard stroke then no it wouldnt be normal to see low floors. so in a sense he is right about it being normal, but if you look at it in a different perspective, who would intentionally use a +4 cylinder on a standard crank. unless im missing something but this is what it appears to me
alot of people use +2 or +4 cranks with standard cylinders (and grind the windows to where they need to be) but rarely the other way around like what your doing
if you would of noticed your banshee with the +4 crank in the standard cylinders. the piston drops below the floors which is just oposite of what your friend has.
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if you add a 1mm you will be around 124.5 and 190exh, i dont think you want to raise it anymore
Otherwise send it out to a shop to be ported to the specs you want for your application
We wouldn't touch the exhaust, just bring the transfer up where it should be with that exhaust duration.
My trx7 port 330 was around 187 and 125 IIRC, I would have to check my notes to be sure.
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somebody probly already mentioned it but i think what you have is for a +4 crankshaft. perhaps esr uses that cylinder for the standard stroke and the +4 to kill 2 birds with one stone. if using it on the standard stroke like your doing, if probly requires a different dome than the +4 that sits 2mm lower so the squish clearance is in the normal range.
if your using a +4 cylinder with a standard stroke crank then yes it would be normal to see the floors sitting low. but if the cylinder was originally intended for a standard stroke then no it wouldnt be normal to see low floors. so in a sense he is right about it being normal, but if you look at it in a different perspective, who would intentionally use a +4 cylinder on a standard crank. unless im missing something but this is what it appears to me
alot of people use +2 or +4 cranks with standard cylinders (and grind the windows to where they need to be) but rarely the other way around like what your doing
if you would of noticed your banshee with the +4 crank in the standard cylinders. the piston drops below the floors which is just oposite of what your friend has.
I certainly understand what the extra stroke does, this cylinder was purchased brand new from ESR for a standard stroke. If my buddy would have noticed this before running it, it would have been sent back. Eddie said it happens sometimes and is normal, he didn't want to fix it. Regardless of why it is like that, he wants to have it fixed (the transfer timing that is) and is the next step I suppose. He just doesn't want to spend the full 450 for a port job.
Don't take any of this the wrong way, this thing still runs strong and has held up well. Mine also runs very good for a little ole 330.
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Believe it or not but 188/120 was pretty common porting setup from allot of builders back in the day because the stock cylinder is right about 120 on the transfers and everybody would just raise the exhaust because it was the easiest.
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Believe it or not but 188/120 was pretty common porting setup from allot of builders back in the day because the stock cylinder is right about 120 on the transfers and everybody would just raise the exhaust because it was the easiest.
I can believe that. I can even do the exhaust myself.
Is there much to be gained by fixing the transfers?
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well if the cylinder was intended for a standard stroke then im stumped why the floors are so low. bad casting perhaps. would like to hear esr's explanation for it. im sure the engine will still run fine but making them floors so low just isnt something that you would do intentionally. im sure esr knows why but it sounds like theyre not talking
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Cometic does sell base gaskets in different thicknesses, factory is .018-.020 so if you tried a .040 or a .060 it will increase the port timing without any grinding and if you do not like it take it out and go back.
but by doing this the compression will drop. So eventually you would want to optimize your head setup also
bumping the transfers up will normally build more mid range power
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well if the cylinder was intended for a standard stroke then im stumped why the floors are so low. bad casting perhaps. would like to hear esr's explanation for it. im sure the engine will still run fine but making them floors so low just isnt something that you would do intentionally. im sure esr knows why but it sounds like theyre not talking
I believe the transfers are so low because Eddie is working with a single casting that he is trying to cover all the bases with.
remember he is tring to please the woods guys, MX guys, the duner guys and the drag guys. All which have slightly different port timing. Then you have 3 different strokes 72, 76 and 77 which throws a huge curve ball when you try to build a woods or MX style motor, the port timing very high with the long strokes.
i am building 2 cr500 based ligers motors for low and midrange power and both them have the transfers setting below the piston at BDC
They are like this because its the only way to do it without welding the exhaust port's roof to lower it. Neither customer wanted the added expense or risk involved in doing this.
Liger cylinders come from CP in a drag style port setup with 196exhaust 128 transfers by adjusting spacer thickness I was able to adjust the Trail bike build down to 188 exh and the SuperMoto bike build down to 192 but on both cylinder I am grinding the transfer ports back up to where they need to be.
the split between the exhaust port and transfers is set by the casting and as a engine builder you have to do what it takes to make it work.
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bumping the transfers up will normally build more mid range power
That is one thing this 310 is lacking. Thanks for the info.
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I believe the transfers are so low because Eddie is working with a single casting that he is trying to cover all the bases with.
remember he is tring to please the woods guys, MX guys, the duner guys and the drag guys. All which have slightly different port timing. Then you have 3 different strokes 72, 76 and 77 which throws a huge curve ball when you try to build a woods or MX style motor, the port timing very high with the long strokes.
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thats what i figured. cover all the bases with one casting. but if your going to use one casting for multiple strokes dont you think its better to cast it for standard stroke with low timings then you can take the ports in any direction you want depending what crank you use and what the engine will be used for ? im sure esr was trying to make it easier for the end user and make it as much of a plug and play as possible by eliminating some of the cylinder grinding but im not sure you end up with ports in the best location by doing it this way. although i see his point of view by trying to make everyone happy
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I know Arlen told me that Esr cylinders are cast for stock stroke and its difficult to make one work on a stroker. Either the transfer ports end up too high with a spacer or you have to run the piston up out the top and cut the dome thin. That is if you want it to have any midrange at all.
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seems like we're just going round in circles here. i dont see why the floors would be hanging low if it was cast for stock stroke. makes no sense at all. unless the casting design was muffed. i can see no other explanation.
what rsss said sounds like a more plausible senario. use one casting for several combinations
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I don't think it needs to make any sense. Eddie said it happens sometimes, I think that means that it's a casting flaw. Regardless of the cause, we're going to try to make the best of it.
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The exhaust port floor below the piston crown is perfectly normal. Graham Bell stated that the exhaust port floor needs to be even with or below the piston crown at BDC or high speed gas flow will be disrupted.
Just something to think about before you start altering trans or exhaust duration, you need to keep in mind the amount of blow down degrees the engine will have.
With your current timing of 187.5 and 120, you have 33.75 degrees of blow down. Which in my opinion is to much for a mx style engine
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some of what them old books said has proven to be inaccurate today 30yrs laters. they were on the right track with a few things but keeping the exh floor level or below the piston isnt one of them.
hell jennings and bell couldnt even agree on what determines a specific engine speed. ive got all them old books and frankly most of the info is useless imo
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bowtie while your at it you may have a gander under the piston to make sure theres not a huge hole out the exh port. real small hole wont cause much harm but keep it to a minimum the best you can. completely sealed off would be even better
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We have another esr 310 TRX9 apart right now and the bottom of the ports are all flush, as were both of my esr 330 cylinders so I know it's not "normal". I'm not worried about the bottom of the ports, just want to get the transfer timing corrected.
He has it scheduled in with Jeff at FAST for correction. There isn't much talk of FAST on here, but be is big on bansheehq and we have seen one of his stock cylinder 250r's run and it ripped.
Good point [MENTION=146]udontknowme[/MENTION], I don't think it is enough to cause a gap with the stock stroke but we will make sure.