Ricco Posted June 25, 2017 Share Posted June 25, 2017 My Yamaha RS125 is throwing out white smoke when I start it up, and for the first few miles of a ride, before clearing up. It's using gearbox oil. Seems the right hand crank seal has gone. Does anyone know if the seal can be replaced by removing the clutch assembly, or is it an engine out job and split the crankcases? Thanks for any replies. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 25, 2017 Moderator Share Posted June 25, 2017 Engine out. It is technically possible but in the normal scheme of things either the crank seals have gone then pulling the rubbish/air through the crank seal does for the bearing. Or the bearing has gone and the seal cannot do its job because of the movement. Best advice is change out the crank seals and bearings. Link to comment Share on other sites More sharing options...
Ricco Posted June 25, 2017 Author Share Posted June 25, 2017 I was hoping to not hear that, such is life sometimes! There's no obvious bearing noise at the moment. I bought the bike following it being laid up for 2 years, I guess that's what did for the seal. I haven't done many miles since I bought it. Do you think attempting to change the seal with the engine in situ would just be a waste of time? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 25, 2017 Moderator Share Posted June 25, 2017 if your lucky your bearing will be good and your seal will just be worn or hardened, if you think your bearing is good and you cannot see any movement in the crankshaft, go for it, it's save some work but if it doesn't work you'll have to delve deeper....this is what you want hear eh Link to comment Share on other sites More sharing options...
Ricco Posted June 26, 2017 Author Share Posted June 26, 2017 OK thanks, I have the manual, I guess that will describe how to check for crankshaft movement. Link to comment Share on other sites More sharing options...
kawman Posted July 23, 2017 Share Posted July 23, 2017 Not trying to hijack your thread, but I have the same problem on a 1971 CT 175. What kind of tool will I need to remove the drive gear to replace the seal? TIA Link to comment Share on other sites More sharing options...
blackhat250 Posted July 23, 2017 Share Posted July 23, 2017 No special tools, , the clutch basket Nut, can be removed wuth a rattle gun/socket, a clutch tool will help hold it, slacken the primary gear nut first, or you"l have to jam the crank, [ without the gear/clutch] . , screw self tappers ito old seal and pull out, Link to comment Share on other sites More sharing options...
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