Posted November 4, 201014 yr Hi all. This bike is a 1992 YZ80D and it blows crank case oil out of a bypass hose when it's under load. Anyone hazard a guess as to what the fix might be before I start taking things apart? I've never had one of these apart, but will have to shortly if my daughter wants to keep riding this thing. I have an owners service manual, but it lacks a diagram that might reveal how pressure is building in the crank case under load to blow out oil. It's getting worse so I'll have to do something about it this winter to have it ready for spring. Any insight people here might have to offer would be welcome. Ian Edit - Crank case... not crack.. save me!
December 6, 201014 yr Hi all. This bike is a 1992 YZ80D and it blows crank case oil out of a bypass hose when it's under load. Anyone hazard a guess as to what the fix might be before I start taking things apart? I've never had one of these apart, but will have to shortly if my daughter wants to keep riding this thing. I have an owners service manual, but it lacks a diagram that might reveal how pressure is building in the crank case under load to blow out oil. It's getting worse so I'll have to do something about it this winter to have it ready for spring. Any insight people here might have to offer would be welcome. Ian Edit - Crank case... not crack.. save me! Check oil level , if not overfilled then it is likely to be a worn crankshaft seal , you may as well do both sides . OEM Yamaha ones are expensive but better than pattern ones. Bob
December 6, 201014 yr Author Check oil level , if not overfilled then it is likely to be a worn crankshaft seal , you may as well do both sides . OEM Yamaha ones are expensive but better than pattern ones. Bob Thanks Bob. Got it on the oil level.
December 6, 201014 yr Hi clocker" the piston rings must be worn also "crankcase pressure" is caused by blow-pass [ compression] down side of rings, better inspect while stripped, rebore might be on the cards, measure at skirt of barrel. [you need sizes from workshop manual] ,,,
December 6, 201014 yr Author Hi clocker" the piston rings must be worn also "crankcase pressure" is caused by blow-pass [ compression] down side of rings, better inspect while stripped, rebore might be on the cards, measure at skirt of barrel. [you need sizes from workshop manual] ,,, As I understand it the two chambers have no connection, but if they do and it continues to spew cankcase oil I'll be sure to check the rings and bore, thanks.
December 6, 201014 yr As I understand it the two chambers have no connection, but if they do and it continues to spew cankcase oil I'll be sure to check the rings and bore, thanks. Ah" its a little two-stroke "
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