Keyser Soze Posted September 4, 2009 Report Share Posted September 4, 2009 I picked up 2 1993 YZ 125's for 100 bucks. One is a parts bike, the other looked like it just needed rings. I went ahead and picked up a piston kit, T-shee honed the jug. Rode it for about 10 minutes and compression dropped. It looks like a tiny peice of metal beat up the piston and the ring was chewed up. Everything on the top end looks good. The guy that had the bike before me had the exact same thing happen. Do I need to split the cases and look for the metal thats causing the problem. It seems to me it would be nearly impossible for something from the bottom end to slip past the rings. I look for something broke on the top end, everything looked good. The piston still looks usable. I'm ordering rings and going from there. Any way to get around splitting the cases? Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted September 4, 2009 Report Share Posted September 4, 2009 Does that have exhaust valve (power valve)? There is a needed clearance between valve and piston. Very easy for junk to be sucked/blown up through transfer ports.Might also check that there isn't any junk in the pipe. Quote Link to comment Share on other sites More sharing options...
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