Vintage BMW Motorcycle Owners

Hey out there!
I bought a 77 RS from an estate and the PO had told me the clutch was slipping. The bike is a very low mileage bike so it sat for a long time. When I removed the clutch I found all the parts looked and measured like new except the pressure spring which measured too low. I replaced everything just to make sure and checked the rod and bearing and they looked good. I drove the bike normally not looking to test the clutch (roll on the throttle in 5th at 75mph) for 3000 miles to let everything bed in. The other day while on my morning ride at 75 mph in 5th I felt the clutch slip going up hill. I checked all adjustments were right on, took the clutch arm off and the bearing is good and the rod is free. I have noticed it does not take much pressure in the clutch lever to release the clutch.
Has anyone ever come across a flywheel the is too deep? I can not find a spec for it in any of my books.

Thanks for reading all this, Jim.

Have you adjusted the clutch cable and free play per Tom Cutter's procedure:

http://www.rubberchickenracinggarage.co ... stment.pdf

Yes and put in a new cable.

When you say "...it does not take much pressure in the clutch lever to release the clutch" what does that mean? Does that mean that when you grab the hand lever and just begin to pull it back, the clutch releases? Or are you saying that it takes very little finger pressure to pull the handle back? Can you get behind the transmission and push on the back of transmission lever easily with your hand?

Was thinking...any chance the pressure plate is in backwards?

Thanks for the reply’s.
First the pressure plate is in correctly.
Second while riding on the freeway I can just pull in the clutch lever a tiny bit and it will release.
The complete action of the lever is somewhat easy compared to my old R75/5 and about the same as my 83 RS that I have been riding since 95. (I know they have completely different assemblies)
I’ve had the transmission out twice now everything was replaced with BMW parts. There are no oil leaks or anything to make it slip.
I’m positive there is no hang up of the release parts to keep any pressure on the plate so I am hoping to get the depth of a known good flywheel to compare mine with.

Thanks, Jim.

If you pull the lever in a bit and you feel the clutch release, that doesn't sound right...not enough free play. What I would do is go to the back of the transmission and screw the adjuster on the lever there out a bit which will give you more free play at the hand lever. Then try riding again. If you give that a try, let us know how it works out.

I’ve tried that as well as the 2 different methods of clutch adjustment 1, the 201 mm and 2mm at lever and S.B. Method for the older airheads with first contact at 90 deg of the arm and 2mm at lever. I also have given more free play to see what happens so I do not think it is related to any of the release parts.

Thanks, Jim

I'm not sure what the "S.B. method" is. You say that is supposed to be first contact when the back of transmission lever at 90 degrees. The way I remember that geometry is that the lever behind the transmission should be parallel with the rear cover when you are half way through the movement at the hand lever. That would be the point of maximum leverage when pulling the clutch in. See page 57 of the file:

https://vintagebmw.org/library_data/Doc ... b89ce1.pdf

I think 2mm at the hand lever is too little. If I remember correctly, it's more like 5mm. That's what is it on my /7.

If you've increased the free play at the lever past 2mm to more like 5 and you still get clutch slipping, then I can only think something internally is wrong. Something is not letting the disk be squeezed tight enough to keep slipping.

Kurt, Thanks for the help.
You are right about the 90 deg adjustment I was having a senior air head moment. S.B. Is Snow Bum.
I think if something in the release parts was hanging up my free play at the lever would increase. Also if the piston was sticking the bearing would not last very long.
I am going to try the adjustments one more time just to be sure but I am hoping someone can give me the depth of the flywheel to check against mine if I have to pull it again.
The bike has had this problem before me so after replacing all of the clutch parts and running it for 3000 miles and it still slips something is very weird and I have to find out what it is.

Thanks, Jim