TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: jcs003 on February 03, 2017, 06:00:02 PM
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I have used weisco, wossner, and pro-x on my two strokes and recently did an engine with vertex. I wanted opinions after I did the work. the engine is together, so there is no turning back. reason i chose this piston is, KTM uses vertex as their OEM, and KTM are one of the only two stroke innovators.
please share your opinions and experiences.
Thank you,
John
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I always used a pro x never had issues. Its a heavier piston so my thought is it will last longer then a piston with less material . an at the time of getting into 2 stokes i seen a fair share of broken wiesco piston which help me make the decision for pro x.
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I always used a pro x never had issues. Its a heavier piston so my thought is it will last longer then a piston with less material . an at the time of getting into 2 stokes i seen a fair share of broken wiesco piston which help me make the decision for pro x.
The recent issues with the wiseco ring locating pins pulling out made me stay clear. I have a wossner in my 250r for 2 years now and compression only dropped 10 lbs, with a lot of abuse.
just to be clear. this is all based on the cylinder being bored and honed correctly to match the clearance issues needed.
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Following this thread as Neil is porting a cylinder for me and asked me if I wanted a cast or forged piston for it. And I have no idea. I have always ran wiseco pistons in my quads with no major issues. I do run 24:1 oil ratio though and race fuel in all my quads
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Following this thread as Neil is porting a cylinder for me and asked me if I wanted a cast or forged piston for it. And I have no idea. I have always ran wiseco pistons in my quads with no major issues. I do run 24:1 oil ratio though and race fuel in all my quads
I always run 32:1 and race fuel. I feel this is helpful in engine life, per neil and jerry.
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32 to 1 hp2 oil and a pro x piston same bore for 18 years. Changed piston 2x 1 at 8 years with a ton of hrs an the other piston was still good until the lower rod bearing came apart. Stock 87 crank
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I have not ran vertex, although i am sponsored by them. I have talked to a few friends at vertex and they swear that they are the real deal. I know my 4 poke will have vertex in it next go round. They come with an anti friction coating like wosner as well.
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The key I stress, which ever piston you get, either one needs to be set up proper by the bore man.
Wiseco has had that pin problem in the past, but that problem is long gone. Wossnor went through that same problem as well, with one of mine & I was lucky enough to get a replacement free. They as well have solved that pin problem.
Problem with the pin, with just a hole drilled in, once the pin is pressed into place & piston in an engine & running, pressure was building up & pushing the pin out of place, so what they did, after the pin hole drilled in, there was a little V notch put into the hole to let the pressure out, pin problem solved.
A forged piston, for any & everybody using the engine, bore to piston clearance needs to be set at 0.0030, or else they will end up seizing the engine.
Now for a pro like rider, been on 2 strokes for many years & that rider going to break the engine in a proper way & then heat the engine to the proper temps before blasting off on it, knowing full well the jetting is spot on before they ever put their foot on that kicker, then the piston to bore clearance maybe can be set up a bit tighter, but that operator has got to be strict each & every start up to detail.
Now a cast piston, most know that the cast piston dont grow as quick from the heat as the forged pistons do, so the bore man can set them quite a bit tighter piston to bore clearance than a forged. A cast piston, like if that same pro like rider was going to be operating this engine, bore could be set up as close as 0.0010 with the same attention to detail from the rider just like with the forged.
Pretty much the difference, between the two types of pistons so far as durability, is dependent on the bore clearance it is set up at & the attention paid to the carbs jetting & the care that the operator will provide for that engine.
Compression wise, the forged piston, can stand quite a bit more higher compression than the cast & for a good amount of time/use. Not saying the cast piston cant survive fairly high compression, just that it wont last as long if hammered on regular. I've seen many in high compression set up, the piston would crack right across the top of the wrist pin & engine still running ok, just not like as when first built.
There have been engine builds, where the cast piston set up tight, compression not to high & it out live the forged pistons. There are many riders/racers out there will have nothing but a cast piston in their engines. To each their own I guess you could say, but with either piston, the bore man is the most important part alone with the person tinkering on the carb jetting.
Neil
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I use Wiseco in all two strokes
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nice to hear wiseco got their issues figured out.
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I have used Wiseco for many years. Never had an issue regardless of the oil ratio. I've ran them from stock size all the way up to 363cc now. They have performed very well. The key, as Neil mentioned, is making sure it has the proper clearance for that TYPE of piston. I ran a ProX piston once as well. Nothing wrong with it, I just prefer forged pistons over cast. Looking at it from a metallurgical point of view, forgings tend to be stronger than castings in basically ever aspect. With that said, your original questions was about Vertex. I have never ran a Vertex piston, but would be willing to give it a go.
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The key I stress, which ever piston you get, either one needs to be set up proper by the bore man.
Wiseco has had that pin problem in the past, but that problem is long gone. Wossnor went through that same problem as well, with one of mine & I was lucky enough to get a replacement free. They as well have solved that pin problem.
Problem with the pin, with just a hole drilled in, once the pin is pressed into place & piston in an engine & running, pressure was building up & pushing the pin out of place, so what they did, after the pin hole drilled in, there was a little V notch put into the hole to let the pressure out, pin problem solved.
A forged piston, for any & everybody using the engine, bore to piston clearance needs to be set at 0.0030, or else they will end up seizing the engine.
Now for a pro like rider, been on 2 strokes for many years & that rider going to break the engine in a proper way & then heat the engine to the proper temps before blasting off on it, knowing full well the jetting is spot on before they ever put their foot on that kicker, then the piston to bore clearance maybe can be set up a bit tighter, but that operator has got to be strict each & every start up to detail.
Now a cast piston, most know that the cast piston dont grow as quick from the heat as the forged pistons do, so the bore man can set them quite a bit tighter piston to bore clearance than a forged. A cast piston, like if that same pro like rider was going to be operating this engine, bore could be set up as close as 0.0010 with the same attention to detail from the rider just like with the forged.
Pretty much the difference, between the two types of pistons so far as durability, is dependent on the bore clearance it is set up at & the attention paid to the carbs jetting & the care that the operator will provide for that engine.
Compression wise, the forged piston, can stand quite a bit more higher compression than the cast & for a good amount of time/use. Not saying the cast piston cant survive fairly high compression, just that it wont last as long if hammered on regular. I've seen many in high compression set up, the piston would crack right across the top of the wrist pin & engine still running ok, just not like as when first built.
There have been engine builds, where the cast piston set up tight, compression not to high & it out live the forged pistons. There are many riders/racers out there will have nothing but a cast piston in their engines. To each their own I guess you could say, but with either piston, the bore man is the most important part alone with the person tinkering on the carb jetting.
Neil
This needs to be in a sticky [MENTION=87]havinnoj[/MENTION]
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Just got a new wiseco piston & getting 2 more in the near future.
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I would add to what Neil said and say that the clearance amount would also be dependent on the size of the piston. Any piston for a 350cc or larger needs to be at least .004 clearance. I believe guys running pumas use .005 for clearance.
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I would add to what Neil said and say that the clearance amount would also be dependent on the size of the piston. Any piston for a 350cc or larger needs to be at least .004 clearance. I believe guys running pumas use .005 for clearance.
Yes common sense would would say that the clearance # would change slightly with the piston size. It is a factor to take into consideration vs sticking to a common number that you have heard repeated.
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John, how did you find a Vertex piston for your 250r? I couldn't find where their website showed one. I like some of the technology they are using in their piston. The silicon content to decrease thermal expansion so the bore clearance can be tighter and decreasing piston skit wear. Then the use of the Molybdenum Disulphide coating to also reduce overall wear. Not sure if they are up to snuff or not, but they certainly have some intriguing tech they are using.
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I dont know about that loose of a piston clearance guys, not on a Pro-x cylinder & Wiseco piston.
I set my daughters 330 up 0.0025, on an old junk resleeved Pro-x cylinder, I had got out of my shop trash can in 2004. I broke it in myself for several days. I did do, the heating process on the piston before I had the cylinder bore & fit. That engine ran from 04 to 07 TT racing & only thing touched on it was a head dome replace from me cross threading the plug.
That engine build, was during the time, there were so many saying you cant make those big bores stay alive. I put everything I knew into building it & it did live.
I have a paper somewhere, listing all the hours, gallons of race gas/oil mix, number of laps that engine endured at local & national TT race events through all those years & it was staggering what it totaled out to be.
During that time, she won an AMA National open class TT championship with it as well, so it was not a trailer queen, that old R was seriouslly beat on.
Neil
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I'm not exactly sure what the cutoff would be for using .003 clearance pertaining to the piston size though, Neil. 330cc may be just under that threshold. I do believe exactly what you said about you engine and respect you opinion, but I had a different experience.
I had my first 363 piston set at .003 (technically .00295 by the bore man).This was using a Wiseco pro lite piston. I ran through 10 cycles on the engine prior to even getting on it and riding it. Then I rode it gently for the first time varying the throttle no more than 50% throttle. The engine was running plenty rich and plenty of oil. During the first ride it seized at 50% throttle. Tore it down, and it had a picture perfect four corner seize. Bore was too tight. And I use an amazing bore man. Nobody babies their engines more than me during break in. The four corner seize pretty much tells the story. I then checked with Wiseco and other engine builders. The cumulative recommendation was .004 clearance for that size and type piston. So I had the piston honed and ordered a new piston. Bore man set it up for .004 exactly and it ran fine ever since. That doesn't make this gospel, just been my experience.
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I'm not exactly sure what the cutoff would be for using .003 clearance pertaining to the piston size though, Neil. 330cc may be just under that threshold. I do believe exactly what you said about you engine and respect you opinion, but I had a different experience.
I had my first 363 piston set at .003 (technically .00295 by the bore man).This was using a Wiseco pro lite piston. I ran through 10 cycles on the engine prior to even getting on it and riding it. Then I rode it gently for the first time varying the throttle no more than 50% throttle. The engine was running plenty rich and plenty of oil. During the first ride it seized at 50% throttle. Tore it down, and it had a picture perfect four corner seize. Bore was too tight. And I use an amazing bore man. Nobody babies their engines more than me during break in. The four corner seize pretty much tells the story. I then checked with Wiseco and other engine builders. The cumulative recommendation was .004 clearance for that size and type piston. So I had the piston honed and ordered a new piston. Bore man set it up for .004 exactly and it ran fine ever since. That doesn't make this gospel, just been my experience.
i dont see much correlation between piston size and cold piston clearance. what it boils down to is the amount of expansion of the piston vs the amount of expansion of the cylinder. if you needed .004 to keep from seizing, that suggests to me that the amount of expansion was quit different between piston and cylinder. the old 500cc plated cylinders only called for .002 cold. piston/cylinder expansion must have been very similar
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one other thing, i dont care who bores the cylinder, you can bet your bottom dollar im putting my bore gauge in there to double check the work
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i dont see much correlation between piston size and cold piston clearance. what it boils down to is the amount of expansion of the piston vs the amount of expansion of the cylinder. if you needed .004 to keep from seizing, that suggests to me that the amount of expansion was quit different between piston and cylinder. the old 500cc plated cylinders only called for .002 cold. piston/cylinder expansion must have been very similar
A plated aluminum bore has a thermal expansion rate very close to the thermal expansion rate of a pure aluminum bore. An iron sleeved bore in an aluminum casting has the thermal expansion rate of a solid iron cylinder but close to the weight of an aluminum cylinder.
The thermal expansion rate of aluminum is almost 2 times that of iron. Because of this fact, plated aluminum cylinders typically run tighter piston to cylinder wall clearance than when using the same piston in a iron sleeved aluminum cylinder to get the same operating clearance in a running engine.
I will go into more detail on this subject when I have more time.