I ordered a wiseco top end kit for my 03' CR250 and right after that I noticed that my service manual says to match the piston code (A or B) to the cylinder code(A or B). They do this to correct manufacturing tolerences. I didn't see any choices when I ordered the top end kit so how does wiseco get around this? Do they just make it somewhere in between A & B and hope it works. I guess you have to buy OEM pistons to get perfect clearance specs. I do have a digital caliper so I will make sure it is within spec before installing.
Wiseco Pistons not as good as OEM???
- Thread starter JD-250
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JD-250 said:
If you are measuring with a caliper you have no hope of ever measuring it accurately enough to know if you are getting it within spec. You need a micrometer and a proper bore guage.
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- #4
Rich Rohrich said:
Why do you say that? My digital caliper is accurate to .01mm. So measuring the cylinder bore and then the piston should tell me what the clearance is. Besides, a digital caliper is what eric gorr recommends using so If it's good enough for him, it's good enough for me.
jmics19067
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- Jan 22, 2002
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while you might be able to measure the piston with the caliper there would be no way to measure where the cylinder actually wears.The only thing you are going to measure is the very edges of the cylinder where the ring doesn't ride.
Typically forged pistons(wiseco,oem KTM etc) are stronger than cast pistons (Vertex,oem Japanese etc) but recquire more clearance.The forged pistons will expand at a greater rate with heat than cast,thats why it is more important to follow a heat cycling break in period and proper warm up each time you start the bike with the forged piston. In the more common forms of neglect I tend to see more "cold seizures" with wiseco and more broken skirts with cast.
Typically forged pistons(wiseco,oem KTM etc) are stronger than cast pistons (Vertex,oem Japanese etc) but recquire more clearance.The forged pistons will expand at a greater rate with heat than cast,thats why it is more important to follow a heat cycling break in period and proper warm up each time you start the bike with the forged piston. In the more common forms of neglect I tend to see more "cold seizures" with wiseco and more broken skirts with cast.
JD-250 said:
Why do I say that? Because you can't get a caliper deep enough into the bore to measure in the correct area of the bore. Even if you could an experienced machinist would have a tough time getting an accurate read on the bore or piston with a caliper , for the average guy at home it's pretty much hopeless if you are looking to measure the difference between an A and a B sized piston. If all you are doing is looking for a "it's close enough" type general clearance measurement then a good caliper is better than nothing, but you are much better served in the long run by having it measured correctly by a shop or a local machinist who has the proper tools. Piston clearance in a two-stroke is really important for power and long term reliability so doing it right is worth the effort. :thumb:
JD-250 said:
Just a quick FYI as long as we are on the subject. Eric Gorr uses a $700 Mitutoyo bore guage that measures in micons and an equally expensive/accurate micrometer to measure pistons in the engines he builds and the cylinders he handles. He does not use a caliper for work like this and he never has.
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I can measure about an inch deep from the top or bottom of the cylinder. Hopefully that is enough to measure where the rings slide.
Rich: I never said eric uses a caliper for his services, it is what he recommends using to measure the piston for the do it yourself guys. It's listed right on his website under "top end rebuilding". Thanks for the info though.
Rich: I never said eric uses a caliper for his services, it is what he recommends using to measure the piston for the do it yourself guys. It's listed right on his website under "top end rebuilding". Thanks for the info though.
I thought I understood what you were talking about when you mentioned the caliper JD...and assumed you meant measuring the piston. But I think even if you get an inch from the top, I don't see how you can accurately measure the bore.
Back to the original question though, since I am also interested, how does Wiseco make one piston work for both cylinders? If nobody here knows JD, I guess we could call Wiseco.
Back to the original question though, since I am also interested, how does Wiseco make one piston work for both cylinders? If nobody here knows JD, I guess we could call Wiseco.
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JD-250 said:
Unfortunately it isn't far enough down, which was kind of my point. I know you are hoping otherwise, but you really do need the right tools to get any sort of useful measurement.
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James said:
The Wiseco is forged rather than cast and requires slightly more piston to wall clearance then the cast OEM piston. The piston is sized to fit the smallest OEM cylinder with adequate clearance.
Does that possibly result in a rattle in the "B" cylinder?
Also, out of curiousity, why does it seem like the Wiseco when new makes less noise than a new bikes cast piston? Does Honda not take advantage of being able to run a tighter fit with cast?
Thanks Rich!!!
Also, out of curiousity, why does it seem like the Wiseco when new makes less noise than a new bikes cast piston? Does Honda not take advantage of being able to run a tighter fit with cast?
Thanks Rich!!!
James said:
Eric has put more Wiseco pistons in more engines than anyone in the US, and he isn't getting any complaints. :thumb: Seriously, they have proven to be very quiet and reliable.
That has certainly seemed like the case in the last couple of years. :cool:
Rich, how does the newer GP pistons wiesco is pumping out compared to the older design pro-lites? I had one of the GP pistons in my YZ and it was great, just curious if you know if the GP pistons are getting the new forging process only and if it would make'em more desirable. My KX is gonna need a new top end soon, trying to decide on getting one of those ore the pro-lite style cause the GP's don't have the piston port window's.
