1978 Rm 100

[OldBustedandBroken]

Any clues- I've rebuilt a 78 RM 100 and the bike wont move- starts and runs great. Removed the 70 tooth rear sprocket and replaced w/ a 59 tooth, but wont get out of its own way.

Clutch not slipping, not missing, just wont go fast. Maybe 15 mph tops in all gears. Do I need a lower tooth count on the sprocket?

 

[originaldirt]

Stock was 14f / 57r. Somewhere near there should get you some speed. Sounds like the motor is not "coming on the pipe". Check for air box restrictions, exhaust restrictions, carb opening fully, timing set correctly, piston facing the right direction (oops), brakes dragging, etc.
OriginalDirt

 

[OldBustedandBroken]

Original- At an idle she sounds great- like it should- revs up, no misses. No air filter, no silencer. Loud as he** so I expect no exaust restrictions. Rolls easy- so I dont think the brakes are dragging. I'm thinking clutch, figured the timing was right as it starts, idles and revs pretty. Thanks for the reply.

 

[dirt bike dave]

The lack of a silencer may be a big part of the problem. Shortening the pipe can just kill your top end power. FWIW, I had an old TC100 Suzuki where the end part of the pipe (the stinger) could be easily removed. Just by taking that stinger off, the bike lost all top end power but still ran fine at low rpm.