JOHN@NCSUVM.BITNET (09/16/85)
Looking for Info, Does anyone out there still have or know anything about the Yamaha RD series bikes.. I've just rebuilt a 75 RD350 and the left cylinder wants to lock up when a run at sustained high speeds.. The boring was done by the local dealer ( ripoff artists ) and I'm running a one size larger mainjet in the carbs to keep it from freezing up right now... Everything else is Stock... If anyone has any ideas, HELP ME... Over the past 5 years I've owned 6 of these style bikes and I've never had this trouble... John DeBoskey ( That's ME! ) John@NCSUVM.BITNET Ral, NC...
wilson@convex.UUCP (09/27/85)
From what you describe my first guess would be that the piston pin/pin boss
fit is too tight in the problem cylinder. The fact that it takes sustained
high speed running to sieze the piston usually indicates that there is a
localized heat source causing the problem. Lubrication (or lack thereof)
problems often cause one of the piston rings to spot weld itself to the
cylinder resulting in a narrow, well defined scratch in the cylinder wall
while problems like the one you have will display a much wider mark. If
you have such a mark and it happens to be on the left of right side of the
cylinder, I'd go for a new piston pin and maybe a piston too.
Stuart Wilson
Convex Computer Corp.
Richardson, Tx.
{inhp4,allegra,uiucdcs,ctvax}!convex!wilson