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Hi Everyone,

I am new to biking and need some advice. I bought a 1994 Honda CR125R and after getting it home and getting from one side of my property to the other the piston blew.  (Guess the guy who sold it got rid of it just in time) After pulling the head to replace the piston I see it's stamped 53.95mm. My question is would I be okay ordering a 53.94mm or do I need the same 53.95mm?  Any info would be greatly appreciated and thank you.

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Blew? I'm not sure what that means. 

Take off the cylinder. If the piston came apart then parts went into the crank and you may as well count on splitting the case and replacing the bearings. I'd put in a new crank kit. 

If it just seized then you might be able to just put in a new piston. You should take the cylinder to a machine shop or motorcycle service shop and have it looked at. They can measure it correctly, inspect it for damage, and check it for round. Based on their measurement you will be able to get a piston that has the correct clearance. Piston clearance specs change from one type of piston (manufacturer) to another. 

Good luck!

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Hi Everyone,
I am new to biking and need some advice. I bought a 1994 Honda CR125R and after getting it home and getting from one side of my property to the other the piston blew.  (Guess the guy who sold it got rid of it just in time) After pulling the head to replace the piston I see it's stamped 53.95mm. My question is would I be okay ordering a 53.94mm or do I need the same 53.95mm?  Any info would be greatly appreciated and thank you.
Stock size is 54mm. You'll want to hone the cylinder walls at minimum before replacing the piston. Best bet is to buy a slightly larger piston (54.5mm or 55mm) and sending the jug to get bored and matched to the piston, then honed to get the crosshatch pattern. Also get new rings while your at it. May need to play with jets or at least a/f ratio afterwards.

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