I took the clutch system next for restoration, and the situation seems to be bad: One of the steel plates (if not both of them) that is working against the friction plate is bended. The pressure plate has deep scratches in it.
I need help with info regarding the allowed thickness of the pressure plate (p/n 21 21 0 070 163), as I need to know if I still can sent it to grinding. I also need to know the allowed tolerances of the friction plate thickness.
Thank you in advance. Michael.
This information would be in the Workshop Manual. If you don't have one, it contains full specs.
SHOP MANUAL R51/3 R67 R67/2 AND PARTS MANUAL R51/3 R67/2 R67/3
The sections on engine rebuild and electric trouble shooting and adjustment are quite good. There is useful information here that is not in the /2 manuals. The shop manual section is in English, the parts manual section in German. 121 pages. $26.
There is also info here about the similar /2 clutch:
D. Measuring /2 BMW motorcycle clutch backing plate.
E. Measuring the /2 BMW motorcycle clutch friction plate.