1982 model R100RS fork rebuild.

[SteveD]

I'm planning on taking the front end off in the next month or so. The gaiters are stuffed and a fork seal has a slight weep.

Whilst I have it all off, is there anything internal that may be worth replacing? Right click, view image for the whole picture. Cheers.

[ME 109]

I don't think there's a lot to wear out in our forks Steve.

My forks don't have 19,11,20,21 ?
My forks are very basic inside. That's interesting considering the closeness of build between our bikes.

[chasbmw]

There is a BMW upgrade for these forks, I will send you details, all parts except for 1 are available from BMW, improves forl action and removes the clunk. C

[SteveD]

I don't think there's a lot to wear out in our forks Steve.

My forks don't have 19,11,20,21 ?
My forks are very basic inside. That's interesting considering the closeness of build between our bikes.

Yeah, it is, but they are in different years I s'pose. As per the fiche you should have #11(we know they're not always right though), #18 goes to 5/81 and #'s 19, 20, 21 are from 11/82.

Chas, I'll look forward to the info. Cheers.

[chasbmw]

Steve send me your email, to $$$$$$$$chas.newall@googlemail.com¥¥¥¥¥¥¥¥¥, I will send you scanned doc.

[SteveD]

Steve send me your email, to $$$$$$$$chas.newall@googlemail.com¥¥¥¥¥¥¥¥¥, I will send you scanned doc.

Done. Thanks.

[barryh]

There is a BMW upgrade for these forks, I will send you details, all parts except for 1 are available from BMW, improves forl action and removes the clunk. C

Chas

Having an early version of that basic fork design I have a particular interest in mods to the damper valve body and valve washer. Would the "details" be service bulletin 2082 or is it the Mike Fishwick write up. Just wondered if there is something else around that I'm missing. I had no idea parts were still available from BMW and ended up making my own shims and modified valve washers.

[Phil_J]

chas Barry
I have a 1982 r100rs an have that clunk on low speed bump where can iI find info on the mods

Phil

[barryh]

Phil

This type of fork can suffer from noise for 2 reasons . One is if the the damper valve body had free play in the bottom of the stanchion (Mine did). That can be eliminated by shimming or the later sprung valve body. The other source of noise is a topping out clunk. On my forks I determined that this was due to insuffient rebound damping as the fork approaches full extension. As the rebound damping orifice which is positioned 25mm below the damper piston falls below the damper valve washer the oil has no where to go except by leakage past the washer. This is supposed to act as a hydraulic bump stop but in my case the clearance between the damper rod and the washer bore was too great at 10 thou to have enough effect. I have been able to eliminate the clunk by reducing this clearance to 6 thou. I also made the valve washer thicker to reduce it's travel from 40 thou to 20 thou and added a bevel on the top edge. All of this was home made based on the changes in the attached BMW service bulletin.

Edit: It seems pdf files are not allowed. I'll see if I can figure out a link to it.


Ok click on this link (but it's secret so don't tell anybody) and scroll down a little to bulletin number 31 009 83 - 2082-Front fork noise.

https://www.bmwmc.net/bulletinsearch.as ... etinnumber


Here's a detail of the changes to the washer dimensions.

[Phil_J]

Thank for that Barry Looks like a job for this winters service


Phil