75/5 motor races, no reason

schrader7032 · Post by **schrader7032** » Fri Aug 28, 2009 7:12 am

Jim -

Does the engine/tranny behave normally in other situations...like going up a hill? What about taking off in first gear from a stop? Is this the only time that the engine racing happens?

Well, it really comes down to only a few things that could possibly be wrong. If the engine is racing and you're still going the same speed then it could be the clutch, the tranny, or the final drive. Have you recently changed fluide in the tranny or final drive? Any largish metal chunks on the magnetic drain plug? There might be some grey fuzz which is normal.

I'm thinking primarily two places...the output from the tranny and the clutch/input splines. Try and remove the rubber boot from behind the tranny...take the clamp off one side or the other. Peel the boot back enough to see the four bolts that connect the tranny output to the driveshaft. Make sure they're all tight.

The second area is the clutch and its connection to the tranny. How many miles on the clutch? If the clutch were slipping, I would also think the engine would race in higher gears when trying to accelerate. When was the last time you did a input spline lube? The spinning clutch disk transmits it's motion to the input shaft on the tranny through a splined end of the shaft. These splines need lubing every so often, maybe every 15-20K miles. If they don't get lubrication and wear away significantly, then the clutch disk will spin freely and not turn the transmission, thus you go nowhere.

My guess it's one of these two areas.

Kurt in S.A.

VBMWMO · Post by **VBMWMO** » Mon Feb 15, 2010 2:53 pm

on a 1973 R75/5 the motor races for no reason. going down the road and all of a sudden the engine is producing twice the RPM. have checked the throttle cables to see they did not jump out of the adjustment nuts on the top of the bings... jim

bmweuro · Post by **bmweuro** » Thu Jul 22, 2010 4:44 pm

Clutch slipping, pinion nut on the rear drive, flange nut on the end of the driveshaft loose, or if it is a low RPM issue it could be your advance springs.

1eugene445 · Post by **1eugene445** » Sat Aug 07, 2010 6:07 pm

My slash 6 used to race after starting, and it turned out to be the cable for the choke was sticking in the fast idle position. YOu might check to be sure the choke is not causing the problem.
Gene