Took the piston out of the motor and it label 8996a on the top, Never seen that number before any idea on what size this is. I thought it was a 68mm piston, but did ESR have number like this?

Robert

I've used ESR pistons, they usually just have the arrow on them... I would just measure w/ a pair of digital calipers!

Robert- I assume that's not from one of our motors. Since I figure you'll check back here, I forgot to mention that those pistons we were running came from Rocky Mountain ATV- good prices on the wiseco pro-lite...

Robert that sounds like a cast number to me. measure it with a dial gauge.
Kenny

the piston is 68mm when I measure it. Just never seen the piston without the size stamp in the middle of the piston like wiesco does. Brandon, no this motor was a spare one I sold to another guy and race this past weekend and was to lean., but your motor is running just fine.

Robert

What is the MM size on a STOCK bore 250 ? :confused:

66.40 mm stock bore