This could simply be an adjustment problem. The previous owner may have adjusted the clutch too tight, and there was a great story here a couple months ago about a clutch that was totally fried because of poor adjustment.
I have to release the clutch lever almost all the way out before
the clutch catches. It's a 3 1/2 hour drive to the nearest
BMW dealer or days wait for mail order. So that I don't have to
wait too long after I tear into my engine, I'm trying to decide
if I can acquire the necessary parts before hand. I figure I
need a new clutch plate. The way I see it the material has
worn so thin that there is little to catch. Any chance that the
pressure plate will need replacing as well? I recognise I need
to install new tranny bolts (10mm). Any comments or suggestions
from others that have renewed their clutch are appreciated.
I'm riding a 1973 R75/5 ...
There is a bolt on the rear side of the engine that controls clutch cable tightness, along with the screw adjuster on the bars. The clutch cable runs from the actuating lever on the left handlebar down to an actuating lever on the back of the transmission. The bolt adjusts the position of the lever on the back of the trans.
The general procedure is to screw the handlebar adjustment all the way in, then use a wrench to set the clutch so that there is at 1/2 to 1" of play in the clutch lever. Tighten the locknut on the adjustment bolt, then fine-tune the clutch with the adjustment up on the bars. You must leave a little slack in the clutch cable, or you too can eat a clutch quickly.
If your clutch is not functioning properly, either slipping in high gear, not disengaging fully (making it hard to get into first gear), or engaging abruptly, you may need to adjust the clutch activation lever on the transmission. On the back side of the transmission, there is a pivoting lever that sticks out on the right side of the bike and connects to the other end of the clutch cable.
With the clutch fully engaged (i.e. hands off the handlebars!) this lever should be sticking out at right angles to the bike, parallel to the rear cover of the transmission, and should meet the clutch cable at a 90-degree angle. If it is not, then loosen the adjuster on the handlebar end of the clutch cable. Take your wrenches and loosen the locknut on the adjusting bolt, near the center of the transmission cover, on the pivot lever. Turn the bolt to set the clutch lever so it meets the cable at a 90-degree angle, then tighten the locknut on the adjusting bolt. Do not over-tighten these pieces.
Now go back to the handlebar adjuster, and set it so that there is a little play in the clutch lever on the handlebar. The clutch lever on the handlebars should have at least 1/2-inch of free play at the end.
Take it for a trip around the block, and make sure that the clutch disengages fully when you are stopped, and engages fully and does not slip when you are in 4th or 5th gear and apply full throttle. If the clutch is slipping under full throttle, you need to screw in the handlebar adjuster to increase the free play. If the clutch will not fully disengage, and the gears grind when you try to shift out of neutral, then you need to screw the adjuster out and reduce free play.
Ars longa, vita brevis.