xljimmy
10-09-2005, 09:43 PM
I have a atc90 that smokes so I took motor apart yesterday and rings look good. The piston was skuffed around skirt but didnt think it was bad enough to smoke like it did. Then I measured piston, 53.34mm. Bore was 53.95mm. Stock is 50. I think somebody bored it and through a piston in it. Neither was that worn looking and it has little more then .50mm clearance. There wasnt even a ridge on top of cylinder. I dont know the tolerance but that seems like alot to me. I didnt think it could be bored out that much either and cylinder is very thin. It is a 90 cylinder because it says 89cc on it. Hopefully it is usable yet. Taking it in to machine shop tuesday I hope. How far can the be bored?