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[QUOTE="mattyp, post: 1275034, member: 87282"]
hey guys i'm new to these forums, looks like a nice solid community.  Anyways, i have a 2000 YZ 125 that toasted the top end a matter of probably 5 hours of riding time after it had been rebuilt, i bought it in this condition for a really cheap price, and the guy has receipts for the rebuild at a local reputable shop (so it was more than likely done correctly).

When i went to tear down the top end i instantly noticed that the piston had some scoring on the exhaust side, and the ring is melted to the piston on that side, i cant get it off the piston AT ALL  :yikes: .  The other issue that i ran into is the cylinder is scored on the exhaust side and also has a little chunk missing on the intake side.

i was wondering what would have caused this problem as i dont want to have the cylinder re-plated and rebuild the top end and have the same problem happen.

I checked out the reeds and they look OK.

I was thinking it could be a dirty carb maybe or even improper fuel/oil mixture.

I am really at a loss here as to what could have caused the problem, so id appreciate your input greatly, thanks! :nod:
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