how much can a 85 250r cylender be punched out to???

[jd267]

my jug is 0.025 over 0.10 of an inch.... and its still pretty clean had 150psi im rebuilding the bottom end and top end and dont no if 75mm is over kill??? whats the max they can be punched out at???

[Yamaha_Rules69]

You mean yours is bored to the first oversize, .25 mm. The maximum size it can be bored to using the stock cylinder and sleeve would be to 69.5mm. Thats 3.5 mm bigger than the stock piston. I wouldnt recommend boring it that much bigger than it is now, that would just be a wast of a sleeve/jug. If it needs to go one size over to clean it up because of scoring, etc, than do that, but dont bore it that much over thinking its going to give you lots of power, because it wont. If you want the power, look into porting the cylinder, aftermarket carb and pipe, reeds/intake block, shaving the head, or installing a big bore kit with matching parts. There are lots of options you can do to the 250r, and boring wont give you near if any of the power you are looking for when compared to these other mods. Good luck.