Clutch Pack Work - Bolts?

[Mike V]

I wanted to get some opinions on clutch work. I'm getting ready to remove the entire clutch assembly on the 81 R65 restoration project. The motor is out of the bike and the last step in the restoration. I'll be replacing the main seal, and oil pump seals before I start the top-end-job. My question is about the 6 Clutch Housing Cover Bolts, pn 21 2 11 338 680. I've heard both ways about these, some say replace some say it's not necessary. I've never been into the smaller 81 and newer clutch assemblies but doubt there's much difference than the earlier models. Just want to make the right decisions the "first" time. Any opinions on this? And, torque specs? Unless specifically otherwise directed, my comfort level is quite high with Oak's Top End Manual.

[Rob Valdez 79 R65]

All I know about these fasteners is, when it came time to remove the clutch assembly from my '81 donor engine, I stripped out two of the heads!  I didn't know that was possible on an allen type before.

I would replace them for that reason, alone.

I think the threads could stand multi-use, however.

I am hesitant to recommend a torque value.

Justin has a universal table around here, somewhere.

Here it is:
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1223906519

[Bob_Roller]

Replace the six bolts, and the lock washers as well .

Last time I was into the clutch assembly, I settled on 15 ft/lb .

Anything appreciably over this, will get you a stripped out bolt head .

General consensus is between 10-15 ft/lb .

Don't be overly surprised, if you strip a bolt head when you remove the original ones .

You can drill the bolt head off quite easily, with the swing arm completely removed from the bike, even easier, with short drill bits .

[nhmaf]

Yes, replace the bolts & washers.  You will also want (3) somewhat longer bolts   (around 1.5" long will probably be OK) so you can evenly get the cover tightened down against the diaphragm spring.
I also used 15 ft-lbs of torque on the bolts.   As with many things, bring the torque up on them all in a couple stages and do it in a cross pattern to keep things EVENLY squeezed.


IF you go to our wiki section, under Repair->Transmission-Clutch Replacement you'll find a mostly complete article by me on how to replace the clutch assembly, etc. complete with pictures.

Oh, hopefully you have BLOCKED THE FRONT OF THE CRANKSHAFT before you pull the flywheel and replace the rear main seal - if the crank nudges forward and that internal thrust washer inside the engine case drops out of position - you're in for a long and expensive fishing expedition!

[Mike V]

Thanks Guys...great useful information as usual, and follows what my assumptions were. Just to verify, I have a good piece of 1x2 I've fabricated to block the crank with (even a spare bolt & dbl-nut against the inside of the cover works well) and I have a home made flat steel flywheel lock I've built for that operation. Looking forward to the home stretch here on this project. It's been a long time coming and I'm anxiously awaiting sharing some final photos when the motor gets back in the frame and fuel in the tank. Then it's party time!

Vroom!

Mike V. / San Diego

[Bob_Roller]

If you don't happen to have a flywheel lock, I've tried this, and it's works for me .

There's a lip, or shelf cast into the engine case right where the flywheel resides, you can put a large flat blade screwdriver in between the teeth on the flywheel, and then turn the flywheel to put some pressure on it when it contacts the engine case, and it will stay in place while you remove the clutch bolts, and the fly wheel bolts .

Put it on the left side for loosening the bolts, and on the right side to tighten all the fasteners up .

[Mike V]

I wanted to share this information with all of you I received from Oak this morning on the subject of clutch assembly and bolt torque in regards to my original post.  Hope this helps, I have a firm plan now, thanks guys, all of you ...

From Oak>

Re: 1981 R65

"Quote"

Mike:

The R65 clutch bolts have always been a subject of controversy. To save duplication I am copying a previous inquiry with my reply on the same subject and sending it herewith to you. This was already published in AIRMAIL. My opinion has not since changed any.
<snip>
The torque figures for the R65 clutch to flywheel bolts were never published in the official BMW shop manuals. I checked that out in my manual. I also had notes clarifying what had happened. They originally had allenhead screws, then  changed to hex head. I suspect the allenheads were a failure for proper torque setting. The figure supposedly for the hex heads is typed in at 13 to 17ft-lbs. I highly suspect 17 ft-lbs is far too much even for high strength 6 mm bolts.

I would suggest you are doing it OK with a lower torque and using blue loctite.If I had to rework a R65 clutch that is exactly what I would do. The bolts may withstand up to maybe 12 or so ft-lbs without undue stress provided they are high strength,(which they likely are) however there is no sense taking risks. Apparently the factory sensed a problem changing the bolt design and simply failed to follow through with exact correct torque figures. But common sense prevails. I would suggest 11-12 ft-lbs with blue loctite, using the hex head bolts..For the R65 bolts I would use new ones. For the old bolts of 8 mm standard clutches they should be reuseable...      

[nhmaf]

Hmm.


I didn't use loctite on my bolts, but did put a small bit of permatex antiseize to help with corrosion protection.   They went to 15 fl-lbs on my torque wrench without any signs of snapping, creaking, etc.
So far, 3K+ miles on the new clutch parts and no issues.

[Bob_Roller]

In case you're wondering, the allen head bolts, are grade 8 bolts, they're pretty strong, so I know 15 ft/lbs won't do any harm to them .

[Semper Gumby]

OK guys.  I thought the only trouble was with the smaller bolts on the 1979 and 1980 heavy flywheel clutches with the small 6mm bolts.  There was no torque published.  The lighter late model clutch of the 1981 and onward had the 8mm bolts and the published value (in the Clymer) should be OK.

I thought we had decided that no more than 10 ft-lbs with some blue locktite was needed on the 6mm bolts.