my cylinder/piston #'s

well i just picked up my cylinders and pistons from the machine shop. everythings in inches.

pistons 1-4 measured 2.596 inches.

piston standard is 2.5956-2.5965 service limit is 2.590 (makes no sense to me)


block 1-4 measured 2.599-2.5995

block standard 2.5984-2.5992 service limit is 2.602


this is like radio instructions to me, anyone tell me if i need to bore my 903 to a 1015 and get a piston kit? or can i put a set of rings? thanks Joe

kz1k wrote:

well i just picked up my cylinders and pistons from the machine shop. everythings in inches.

pistons 1-4 measured 2.596 inches.

piston standard is 2.5956-2.5965 service limit is 2.590 (makes no sense to me)


block 1-4 measured 2.599-2.5995

block standard 2.5984-2.5992 service limit is 2.602


this is like radio instructions to me, anyone tell me if i need to bore my 903 to a 1015 and get a piston kit? or can i put a set of rings? thanks Joe

you're pistons are fine they get smaller as they wear out thats why the service limit is a smaller number than they measure now. the block is on its way out. At about $70 each you could just resleeve it to the stock bore.

sounds like a piston kit/bore is in order.

pistons 1-4 measured 2.596 inches.


block 1-4 measured 2.599-2.5995

Subtract these two above and that gives a piston to cylinder clearance of over .003" which sounds a bit loose to me (?)

bountyhunter wrote:

pistons 1-4 measured 2.596 inches.


block 1-4 measured 2.599-2.5995

Subtract these two above and that gives a piston to cylinder clearance of over .003" which sounds a bit large to me (?)

thats what the machinest said. 3 thou. then with honing i would add another thou.

Sounds like you got it under control!

DoubleDub wrote:

Sounds like you got it under control!

hey man, i got the bike for free, what di i expect?:woohoo:

.004" is looser than I would prefer to run for clearance. Good ballpark is .001" for every inch of cylinder bore. I'
d set up with .002 on the end cylinders and .0025 on the inside pair.

JMO