2001 YZ426 Cylinder Markings

Hey, I am redoing my top end and found these markings in the cylinder.

Does anyone know what the mean?

I just installed a standard size piston on a little worn cylinder.

I haven't run it yet.

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They don't mean anything to anyone outside the factory.

 

There is only one size piston available from Yamaha because the bore cannot be resized.  When you imagine the cylinder wearing to a larger size, bear two things in mind: The most it is allowed to wear before it needs to be replated or replaced is .002", and the wear only happens in part of the bore.  If you put a larger piston in to fit the loose part, it would be too big for the rest of the bore. 

They don't mean anything to anyone outside the factory.

There is only one size piston available from Yamaha because the bore cannot be resized. When you imagine the cylinder wearing to a larger size, bear two things in mind: The most it is allowed to wear before it needs to be replated or replaced is .002", and the wear only happens in part of the bore. If you put a larger piston in to fit the loose part, it would be too big for the rest of the bore.

Thanks for the info Gray.

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