25 CC

[KellyVB 75R90S]

As most of you know, I have owned the R90S for over 30 years and put thousands of miles on her. She even has an Iron Butt Certification. The bike belonged to my brother before me, there has never seemed to be any oil in the swing arm, even when he owned it.So I finally decided to find out how much there was actually in it as i'm servicing her for a Tail of the Dragon run in June. SO, I drained the final drive and the swing arm, the was some in the swing arm. Every time I have filled it up with 5 oz I also filled the final drive up as well of course, which after reading on Duane's site I find out why the back brakes have NEVER been any good, (There soaked with oil from the overfilled final drive\]) I filled up the swing arm again with 150cc of oil and let her set for 2 days. Checked it and there is only 25cc in the swing arm, the rest has gone into the final drive. Is this a quick fix or do I need to just put 25 cc in and fill up the final drive to normal and go on my way, keeping in mind that it has always been like this? (30 years +)

Thoughts??

[Major Softie]

You need to replace that seal. The good news is: you will probably retain rear brakes from now on.

[KellyVB 75R90S]

Ok, so the question is, how hard is it to change? have any of you changed one? can i do it my self?

[Duane Ausherman]

You must seal up all three paths from the swing arm into the final drive. Only one of the three is an actual seal.

[KellyVB 75R90S]

The oil actually leaks into the final drive almost as soon as it is put in, so wouldn't that be the shaft seal. having a hard time understanding the other 2 paths you talk about. I know its not going in the transmission. What special tool do i need to get the ring out? Part#?? . I was looking at the parts breakdown and it shows the shaft seal goes in after the ring.

[Duane Ausherman]

That may well be the major leak, but still one must seal each path, or you will be going back in later to seal the slower leaks.

Sorry that I don't know how to make it more clear.

[KellyVB 75R90S]

I think I understand, you say I need a special tool to remove the threaded ring. Where can I get one? can I make it? Need to get this done fairly quickly.

Thanks
Kelly

[Airbear]

To get to the seal you need to hold the splined 'clutch hub' to remove the nut ...



The tool you need can be made from a discarded driveshaft with a bit of cutting and welding. Here is a fine one made by ME109 ...



The torque setting for that nut is listed at 150-165Nm in my Clymer manual.

[KellyVB 75R90S]

Cool, what about the threaded ring? Don't I have to remove that? I know that takes a special tool, where can I get it or can I make that as well? I know someone here has done this job.Please chime in here. If I take the final drive into someone what might it cost to have this done??

Thanks
Kelly

[Airbear]

Kelly, I haven't had to replace the seal, just re-torque the nut. But looking at the exploded diagram in my Clymer it looks like the the seal is outboard of the threaded ring. Ok, just checked further and It is part 5 in this Max BMW fiche image:



If you are just replacing the seal it is really only a few minutes work for somebody with the tools, so maybe take your FD to a shop. You would also replace the paper gasket when re-installing.

I have no idea about the other two paths for oil that Duane mentions. Perhaps he will chime in.