Originally Posted by STYLNLT
Jack Oil you say. Is there a specific density or brand recomendation?
Top Up Shock Remote-Preload Oil
(Simple shock rejuvenation)
I read about this on the BMW Sport Touring Website. Aparrently quite a few BMW riders realized that their remote rear shock preload adjustment did not have the range it once had. The hydraulic preload adjustment circuit (which is independednt of the damping oil in the shock) seems to lose oil over time. Nobody can explain where the oil goes but someone figured out how to fix it.
The adjuster on my 95 GS had a lot of slack in it when the suspension was unloaded and I had wished for more adjustment range when I carried a heavy passenger. However, I had never compared the adjustment range to that of a new bike, so I was blissfully ignorant of what was missing.
Once enlightened, the repair is almost trivially simple. Here's what to do:
Back off the adjuster all the way.
If you can reach it, it is much easier to break the banjo bolt (arrow) loose before you unbolt the preload adjuster (circled allen bolt)
Once the adjuster is removed, turn it upsidown and remove the banjo bolt and hose. Be careful not to lose the copper sealing washers. Hold the hose up while you work on the adjuster so the oil in the hose won't drain.
Push the piston down and top up the oil. Some people have used hydraulic jack oil. I used whatever was handy.
This is how much adjustment range was recovered. In these photos the adjuster is turned until resistance just begins, indicating that preload pressure is being applied to the spring. Before this repair, it appears that I should have had it set on HIGH just to get STD preload. HIGH preload was unobtainable even with the adjuster bottomed out.
This was an extremely simple, easy way to rejuvenate the shock preload adjustment. The whole operation took less than twenty minutes, including taking the photos. (I still have no idea where the original oil went.)
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