YTM200 piston ?
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The biggest possible size is 70mm for the original 200 cylinder.
You have to install a bigger sleeve, if you want 70.5 (or bigger) piston.
The biggest possible size is the 73mm piston from Wössner piston. These pistons should be also available in the US.
-> You can contact me, if you can not find a US-reseller/dealer for Wössner.
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Please use the service manual. Everything is written into it.
It doesn't matter which piston do you use (original or high compr.), the procedure is always the same.
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1,761 Posts
What kinda cc's would it be with a 73mm bore? Just curious...
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How much wear do you have on the cylinder? I know that I could get away with a hone but that's because I only have 3700 miles on my 2010.
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So I could turn my 200 into a 233cc beasty with a re-sleeve?! Is the mouth of the stock case wide enough to accept a 73mm piston? If so, I may have another winter project? Has anyone done this before? Is this or a 72mm bore the set-up of the european 225's?
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The overbore shouldn't be expensive.
My customers are paying for a +0.50mm oversize 46 Euro (~60 USD).
If one a customers would go to the same shop (a really good shop), he would get it cheaper (not much, but a bit cheaper).
75 USD (55 Euro) is OK, not a really good price, but OK.
My customers are paying for a +0.50mm oversize 46 Euro (~60 USD).
If one a customers would go to the same shop (a really good shop), he would get it cheaper (not much, but a bit cheaper).
75 USD (55 Euro) is OK, not a really good price, but OK.
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1,761 Posts
A bore around her is around $55. Shop around.
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764 Posts
Yes, you can do it with this tool, but.....
Only a professional should do it.
You need the exact rpm and up/down movement to get the perfect cross-grinding.
The other problem is to get the same diameter on every position.
A friend of me told me about a new honed cylinder, but the form was like an egg not a circle.
Only a professional should do it.
You need the exact rpm and up/down movement to get the perfect cross-grinding.
The other problem is to get the same diameter on every position.
A friend of me told me about a new honed cylinder, but the form was like an egg not a circle.
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6,740 Posts
.5 mm larger diameter is only .25 mm removed from the cylinder wall. .25 mm is a very little bit! I will think about it and maybe practice on a junk cylinder if I can find one.
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Yes, it's just 0.25mm, but the bore must be exact.
The tolerance must be 0.01mm, not bigger or smaller.
Do you have a micrometer gauge?
If not, forget it.
The question is:
-> Do you want to save a bit money?
But you have the risk, that your piston could die after some miles?
- too small piston clearance -> piston squeezing -> new piston, new bore
- too big piston clearance -> low compression, exhaust gas into the crank case -> new piston, new bore
The result, you will have to pay much more money and you will have a lot of trouble.
-> Or do you want to pay a bit more money?
But you will get a perfect result.
The tolerance must be 0.01mm, not bigger or smaller.
Do you have a micrometer gauge?
If not, forget it.
The question is:
-> Do you want to save a bit money?
But you have the risk, that your piston could die after some miles?
- too small piston clearance -> piston squeezing -> new piston, new bore
- too big piston clearance -> low compression, exhaust gas into the crank case -> new piston, new bore
The result, you will have to pay much more money and you will have a lot of trouble.
-> Or do you want to pay a bit more money?
But you will get a perfect result.
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1,761 Posts
Touche' Tony, touche'.
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Grab a spare cylinder and practice doing .25mm bores on it. When your confident, go for it. It's not rocket science, just make sure to practice and get the cross-hatching right with different drill speeds and the plummeting speed into the cylinder. Don't try to do it with a hand held drill!
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