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Rebuilding the front forks '76 R90/6

plehman

plehman

New member
The problem
I notice on a sharp bump a nasty clunk from the front forks. I've adjust and tightened the steering head (80 lbs on that center bolt!) and checked all obvious sources for looseness. I've been told it might be the bumpers inside the spring/shock assembly. These I've ordered and am going to dive in. Pull out the spring, replace the bumpers (big on bottom, smaller one up top), replace the fork fluid and all will be well. In theory.

Question
I can't find a good DIY on this procedure. The Haynes manual is alright, but vague (trying to cover so many models). I looked for a Snowbum article, but couldn't find a step by step on the inner parts.

Any suggestions?
thanks
 
I found an article on the IBMWR web site for overhauling the fork on an R100/7. The fork on your R90/6 would be virtually identical to the /7. It's easier to do the work on a bench, but you can do it with the yokes and fork tubes left in place. Be sure to read over the entire article at least twice to get a solid grasp of what is being described.

http://www.ibmwr.org/r-tech/airheads/fork_overhaul.shtml
 
For me, the hardest part of the whole procedure is removing and re-installing the fork legs back into the triple clamps. If you plan on servicing the steering bearings, then remove both fork legs, otherwise one at a time works. As James suggested, doing it on a bench makes life easier on the back. Cut up a used soda/beer can to use as shim'guide for reinstalling the damper rod to collapse the rings. If you are removing and reinstalling the lower leg bottom cap, use some gray sealant on the threads when reassembling(just a little). I generally use a can of brake cleaner per fork leg to blast away all the debris from the bottom bumper and general cleanup of the parts. Overall it is not a difficult job, I've done a set in an afternoon, but then I've done a few. Good luck and let us know how it went.
 
rebuilding front forks 76 R 90/6`

Step 1, If you haven't done so already join the Airheads Beemer Club (www.airheads.org)

Step 2, contact MA Airmarshal Tim Hille, not too far from you.

Step 3, attend one of their frequent Tech Days and get lots of help and instruction to properly do the job. Their next Tech Day is upcoming Jan 6th.

Friedle
Airhead #46
NY AM
Airheads BoD
 
Friedle said:
Step 1, If you haven't done so already join the Airheads Beemer Club (www.airheads.org)

Step 2, contact MA Airmarshal Tim Hille, not too far from you.

Step 3, attend one of their frequent Tech Days and get lots of help and instruction to properly do the job. Their next Tech Day is upcoming Jan 6th.

Funny, I just did that a few weeks ago. And they did a demo of this procedure at the last meet. I'll be there next time.
Click to expand...
 
Out on the bike in the cold today. I'll read the suggested articles a few more times and give it a try next weekend.

Thanks a lot for the suggestions.
 
plehman said:
The problem
I notice on a sharp bump a nasty clunk from the front forks. I've adjust and tightened the steering head (80 lbs on that center bolt!) and checked all obvious sources for looseness. I've been told it might be the bumpers inside the spring/shock assembly. These I've ordered and am going to dive in. Pull out the spring, replace the bumpers (big on bottom, smaller one up top), replace the fork fluid and all will be well. In theory.

Question
I can't find a good DIY on this procedure. The Haynes manual is alright, but vague (trying to cover so many models). I looked for a Snowbum article, but couldn't find a step by step on the inner parts.

Any suggestions?
thanks
Click to expand...

Hi Phleman,

You can take a look at these write-ups on the procedure. The forks for the /5 and RS are essentially the same as your /6.

I strongly suspect one, or both, bumpers have dissolved.

1973 R75/5

31 BMW 1973 R75/5 Install and Align Front Forks

31 BMW 1973 R75/5 Rebuild Front Forks

http://brook.reams.me/bmw-motorcyle...t/31-bmw-r755-replace-steering-head-bearings/

1977 R100RS

31 BMW 1977 R100RS Remove Front Forks, Handle Bars, Steering Stem, Fork Lock

31 BMW 1977 R100RS Replace Steering Head Bearings, Rebuild Front Forks


I hope this helps.

Best.
Brook Reams.
 
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