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YZ 125 Piston Problems!

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My bike has a standard piston in it, when running its making a slapping sound. so when i took the head off, I noticed it had about 1 mm of play side to side, I need to buy a new one but im not sure what to do.. should I buy/Do i need to buy a slightly bigger piston, and bore my bike out to a 127? just hone it out and put a bigger piston? im really stuck here. I really dont want to spend alot on it as Im also getting my bottom end done, which is gona eat up alot of my money. Im just looking for the least expensive way to fix my top end.

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eek,

how does the cylinder walls look? how bad is the damage?

are you sure the piston is standard?

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1mm is trashed Dude. Bet your just seeing the movement of the piston with worn skirts. Realy need to pull it down and check the cyl and replace the top end. Check the cyl from top to bottom and realy mic the middle good to see if its out of round.

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the Cylender walls look fine, No damage. no skore marks, none on the piston either. thats why im puzzled, if its slapping around the way it is when i move it with my finger than i dont know how notings damaged. and yes its a stock piston. I just dont know what to do like what size piston to get, how to actually check to see if the bore is messed up, weather to hone it, or bore it, really not sure. like everythings fine, crank, rod, cyl, everythings in good shape.

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I would take the piston and cylinder down to any local shop and ask the mechanic to take a quick look at it. In my early days of fixing bikes, I learned a lot by doing this. Some shops are more helpful than others, most will help you, knowing you will likely buy the parts from them if they are friendly. It will only take a mechanic 15 seconds to measure the bore and look at your piston and tell you what needs to be done.

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I would take the piston and cylinder down to any local shop and ask the mechanic to take a quick look at it. In my early days of fixing bikes, I learned a lot by doing this. Some shops are more helpful than others, most will help you, knowing you will likely buy the parts from them if they are friendly. It will only take a mechanic 15 seconds to measure the bore and look at your piston and tell you what needs to be done.

Fantastic advice !!

a. you may learn something

b. support the local shop

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ok guys, went back and looked at the Cyl, I waaay over estimated the Gap, its about half a mm of play or less. none the less its still slapping around and im not sure what to do about it. I'll bring it to the shop though and see what they say.

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