piston boring specs

[revoarcher]

I am boring out my FE 290 .25mm and was wondering if anyone knows the proper piston-bore dimensions? What is the minimum and maximum piston to bore dimensions or do I just have them bore it .25 over standard dimensions and that is close enough? I am asking because when I had my snowmobile bored out the machinist wanted the piston and the proper manufacturers clearances so he could measure them and bore the cylinders to the exact dimensions.

[Nicky]

give him the piston and tell him three thousandths clearance. he should be able to take it from there.
Nick

[revoarcher]

Thanks I was looking on the net and found some info for a 91 and it said piston to wall clearance of .0006 in to .0018 in that would be under .003 to just over. would this be the same for the fe 290 because I don't want to bore it out to much? I would like to keep it as tight as possible without it being to tight. Would .002 be to tight?

Thanks for the help!

[Nicky]

I just went through all of this with my 290 and .003 was the number I wouldn't go any less. you may have a chance of it locking up. .003 is the total clearance. so that would be one and a half thousand per side. The Machinist will bore it .003 more than what the piston measures