R100 Clutch pushrod too short?!?

[20774]

Post #16 shows what appears to be a part number "...242-372". From what Snowbum wrote on this page in the red box at the top:

http://bmwmotorcycletech.info/clutch.htm

This part beefed up and eventually the part number was 21-21-1-338-722. So given that you have the older part number, my thought is that you have the less beefier clutch parts. I tried to follow Snowbum's part number changes, but I get a little lost.

 

[CaptDistraction]

Post #16 shows what appears to be a part number "...242-372". From what Snowbum wrote on this page in the red box at the top:

http://bmwmotorcycletech.info/clutch.htm

This part beefed up and eventually the part number was 21-21-1-338-722. So given that you have the older part number, my thought is that you have the less beefier clutch parts.

Now my eye is focused on that red box on Snowbum's page. It does seem as if I have at minimum the earlier, beef-less, clutch carrier (nee "flywheel"). I cannot be sure about the other parts without finding part numbers on them. It is clear that in this situation Snowbum would suggest I replace everything:

"If you are overhauling a 1981 model with original parts, it is a VERY good idea to replace all the parts that were later updated ...which is nearly everything!"

Unfortunately, that is not an option for me.

Also, while I am glad to have learned this about the uniqueness of the 1981 clutch package, I don't think it gets me closer to solving the pushrod mystery. All of these parts worked together on this bike before it was taken apart. The only thing that was changed was the actual clutch disc - the one that was removed was used a core (it was near its wear limit) and traded for a refurbished one. As you can see it was all assembled correctly. Beef-most or beef-less version aside, the pushrod should have remained the correct length - the length required to make contact between the diaphragm spring and the clutch lever on the back of the transmission.

I also noted that Snowbum states (in RED) "During early production of the 1981 bikes, some bikes had factory installed washers between the carrier & cover. Those are NOT to be used when replacing these parts." I do not know if he means do not put the washers back when reassembling the original parts, or if he means when reassembling one's newly purchased completely new upgraded clutch parts. I'm sure he definitely means the latter, but I don't know if he means the former as well...

 

[AntonLargiader]

Did you ever measure the thickness of the friction disk?

 

[pglaves]

OK Now let us see all of yhe throwout bearing assembly pieces.

 

[CaptDistraction]

Did you ever measure the thickness of the friction disk?

The worn friction disc that was replaced was 5.1 mm thick. The one that is installed now is 6.3 mm thick.

 

[CaptDistraction]

OK Now let us see all of the throwout bearing assembly pieces.

Please see the first pic in post #5. If that is not what you are referring to, or if there is something else you want to see, just let me know. Thanks!

 

[CaptDistraction]

I feel like it would be useful for anyone pondering this problem to see the transmission output shaft. It is also a good excuse to bump this discussion back to the top of the forum, as there has been no action here in a little while

 

[20774]

The transmission input splines look pretty good. So, if you were to input the clutch pushrod at this point and position the aft end approximately where it should be, how much of the pushrod sticks out past the input splines?

 

[AntonLargiader]

The stock pushrod is about 225mm long... My wooden replacement shows that I would need a pushrod that is about 260mm long to fully engage the clutch actuating lever on the back of the transmission.

That doesn't make sense. The installed pushrod only has about 12mm (depending on clutch wear) of forward room before it bottoms out against the flywheel. There's no room for a pushrod that's 35mm longer. Does your pushrod taper stop against the spring center, or has it worn its way through?

You can mock the parts up yourself to see, but the correct fully-assembled position of the rear tip of the pushrod is roughly in the middle of the cover bore.

You do not have the latest flywheel. Yours has gaps between the clutch mounting ears and the ring gear mounting ears, while the later one (722) is more of a continuous stamping with webs that connect the ears.

 

[AntonLargiader]

Have you learned any more about this?