Hi hope someone can help 'cause this is driving me nuts. My son managed to blow his Yamaha Jog rr engine up. We have totally rebuilt it with new crankshaft, bearings both ends, piston and rings, cylinder head etc also put on new variator rollers, new exhaust, all gaskets renewed etc. The problem is that the engine now runs fine and the back wheel runs free and fast all the time the bike is on the stand. As soon as he tries to ride the thing the power is rubbish on the flat and the slightest uphill bit is a nightmare almost stops. We have tried everything we can think of and can't figure this one out. Someone please help need to get him mobile again fed up with being a taxi!!!!!
chanses are the belts sitting cocked (the variator spacers not in the right places) if everythings assembeled as it was befor with no jetting changes the only thing that can be at fault is somthing during the build. look over everything 3 times as often the complicated mind dismisses the petty problems
by new rollers, did you replace with the same weight? also when you fitted the crank did it spin freely? somtimes a few good smacks each end of the crank free the pressure on the mains and let the motor spin more freely. thats clutching at straws though.
