What causes blowby? When I last removed the cylinder of a 1999 CR125 (highly modified for kart use) I see a brown blowby mark (fairly large) above the exhaust bridge. Is this because the piston is rocking after TDC and causing the ring to come away from the cylinder? I see no blowby through the ring gap (which is now .020") Also lots of brown under the ring on the piston. Piston clearance is 0.004" measured in the skirt area with a feeler gauge.
