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Well fist things first i dont really know much about 250r's since this is my first one after trading my rm250 for it. so bear with me.

Well i decided to tear down the motor since i only had about 110psi of compression. everything looked good visually and i was getting 2.62in (66.54mm)all around the the cylender so im guessing its been bored .02 over but the top of the piston says 50mm. I dont understand that.

the rings on the piston are square and i was told if they where worn they would be rounded on the edges. is that wrong?

my main question is that could i get by with just honing the cylinder and putting new rings in. Im trying to get this ready for a race at the end of this month and dont have a lot of time or money. i plan on upgrading to a bigger bore later on anyways so it dosnt have to last forever i just want it to be running strong when i race till i get the money to upgrade
 

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.5 is .5mm which is .020" over. 1mm = .040"
You need to have your cylinder more accurately measured straight & round, using a good dial bore gauge.
JT
 

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You should have it mesauered like John said. In the mean time. Post pictures of the piston top and sides.
Up grading to a bigger bore beyond what it needs to clean up is just a good way to lighten your wallet, unless your going significantly bigger usually well past the standard range of pistons available.
 

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More good advice from another knowledgeable newbie; it’s refreshing to have all of this new blood.
For big bore conversions; Like iceman said, at least a 3mm oversize for any power boost. Back in the day, we always would bore Honda 4 strokes 3mm over. The most the standard Honda cylinder would go.
 
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