Piston to cylinder clearance

[ridingred336]

Hi my name is mike and i am new to this forum. I just picked up my first 250r its a 86. I have the top end apart and it was bored over to 67.25mm with a wisco piston. When i measure the piston to the cylinder it is at .006 is this to much clearance? Any help would be great thanks.

[C-LEIGH RACING]

To me it would be, because I consider it time to rebuild at less than 0.005

If your measuring the old piston & then the cylinder bore & compairing the two & coming up with that clearance, it is probably ok, because what you need is the measurement from a new 67.25mm piston to know how much wear is in the cylinder bore.

Wiseco piston, new bore, 0.0030 piston to cylinder.
A cast piston, you can run piston to cylinder bore clearance a lot tighter than a forged.
I have set them up 0.0010 to 0.0015 before to make them last.
Either one though, you need a good long break in process.
Neil

[machwon]

Sounds like its a used bore and piston? I'd check the bore against a new piston, don't forget to measure the pistonat the bottom.