When they talk about boring out a cylinder, is it per side or on the diameter? And is .020 in inches or mm?

 

<div class="FTQUOTE"><begin quote>When they talk about boring out a cylinder, is it per side or on the diameter?</end quote></div>
Diameter.
<div class="FTQUOTE"><begin quote>And is .020 in inches or mm? </end quote></div>
Depends on who your talking to. I always talk in inches. Common sizes over in the US for automotive is 0.010, 0.020, and 0.030. A lot of people that deal with motorcycle engines talk overbore in MM.

 

Ok thanks. So, if I buy a wiseco piston that is .020 over, and my bore right now is stock at 74mm, then I would bore it out to 74.508mm. I do realize to not bore until I actually measure the piston.

 

when you bring your jug to the machine shop they measure the piston then measure the cylinder...they do some math taking into consideration the piston to cylinder wall clearence and go from there. its actualy easier to do then explain. they will need to know what the piston to cylinder wall specs are.

 

It might not be a bad idea to take the cylinder in to the machine shop (if you don't have inside micrometers). It might only require .010, or if its badly worn or damaged, it might need 030...