Clutch issues

[stubmw]

Hi all. Just stripped the clutch down on a 1978 engine (heavy flywheel) to grease input gearbox splines and check general condition of everything in there. The bike does have a grabby clutch, although cable and adjustment is all good. So i thought I'd delve a bit deeper.
On inspection all the components seem in very good condition and all mesurements are within spec. I see the white dots from the factory on cover plate and flywheel were at 90°apart  and not 180° and couldn't see one at all on the pressure plate! Any thoughts?
But, the main issue is, upon reassembly  I'm torquing the hex bolts up evenly on the cover plate to Haynes recomendation of 23Nm - 17 lbf ft and, oops they start to shear off!! These are new bolts, M6, 10.9, 10mm spanner, high tensile. Have i been supplied with the right ones? Is this torque  setting right? Is my torque wrench bad i wonder! Any help greatly received.   Stu

[Barry]

17ftlbs does seem to be the recommended value but it's awful high for an M6 bolt even in 10.9 quality.

If you look at standard torque tables for an M6 10.9 you'll see a figure of 11 or 12 ftlb at the most and that's for dry threads.  I'd be inclined to use that as a maximum figure.

[stubmw]

17ftlbs does seem to be the recommended value but it's awful high for an M6 bolt even in 10.9 quality.
My thoughts too Barry. Looks like I'll  be doing them up by hand.

[wilcom]

I looked up those bolts on Snow Bum's site and sure enough your issue is addressed. Snow Bum sure uses a lot of words, but if you take your time almost everything is in there....... finding it is another issue LOL


From: http://bmwmotorcycletech.info/clutch.htm

".The early R65 and R45 had smaller clutches than the larger engines did.  The 1979 & 1980 had 6 x 1.00 mm CLUTCH bolts.  The amount to torque the clutch bolts to the flywheel is NOT listed in early BMW literature; & is wrong in some later literature.   There is some confusion over this.  BMW originally had Allen head bolts, then later went to hex head bolts.  I suggest using the hex head bolts. Some published figures are as high as 17 foot-pounds for the clutch bolts (any style).  That is WAY too high, even for high strength bolts.  I suggest 88 inch-pounds (7-1/2 foot-pounds) for the 1979-1980.   Use clean & dry threads, then coat before assembly with a light amount of Loctite BLUE.   It is possible that up to 10 foot-pounds is OK, but that would be for high grade bolts only.   Any book figures you see that say 17 foot-pounds, or 15 foot-pounds, are WRONG!"

[stubmw]

Thanks wilcom for finding that, that's all the info i needed. I do seem to get lost in snowbums writings,  although i didn't check this specific  issue out there,. He is a great source for information.
 I'll get some new bolts tomorrow and try again.
 

[stubmw]

Clutch went back together with new bolts. Forgot to say earlier, the clutch disk was a bit glazed so i scuffed it up a little and it's  working 100% better, no grabbing and running well.