A) Upper left photo shows how pipe clamp is used to depress the metal plug in the top of the fixed tube.
B) Upper right shows assembly in clamp, with 1" PVC fittings (described below) to prevent the damper rod from compressing while the top metal plug is depressed.
C) Lower left shows the detail of the lower end 1" PVC fittings.
D) Lower right = detail of the ABS pipe and coupler used to tap in collar and seal.
E) What I don't show is what you have to do if you put oil in the shocks before putting them back on the bike. Put the assembly in the bar clamp, and place another rubber-faced clamp on the fixed tube, immediately above the tube to tube dust cover. Then screw down the bar clamp, with a piece of wood, large nut, etc., on the top metal plug. Run it far enough down that you can slip in the little retainer clip and into its slot.
There are a number of sites describing BMW fork seal changes, but I found them somewhat confusing and were not specific for this motorcycle. After doing this job and making some mistakes, I thought I'd post this online to make this maintenance more straightforward. Description is for one fork at a time. The "fixed tube" is the tube that is attached at its upper end to the bike. The "sliding tube" is the heavy aluminum part that attaches to the wheel and slides up and down on the fixed tube. Other than standard tools, you will need the following: a 1 & 1/4" PVC coupling, with its internal stop rib filed out, and, a 17" length of 1 & 1/2" ABS or PVC pipe, that is reamed out with a hole cutter bit, to 41mm (1 & 5/8"). Note: light wall PVC may do the trick without having to be reamed, but I couldn't find any. If you decide to remove the fixed tube before removing its top plug, you will also need a 1" PVC coupling with a 7" length of 1" PVC pipe inserted into it.
1) Get the bike stabilized with front wheel off the ground.
2) After removing the front tire/wheel, the ABS sensor, brake caliper, and fork cross-brace, place an oil pan under the tube end. Remove the small fork oil drain bolt , then remove the damper bolt in the very bottom of the fork tube. Oil will start dripping out.
3) There are two ways to expedite oil drainage: a) slowly pump the outer tube up and down, but be aware that oil will vigourously spurt horizontally from the small oil drain hole - keep your pan held right under it to avoid a big oil mess; b) up at the steering head, remove the dust covers on the top of the fixed tubes. Then with big muscles and three hands, depress the metal plug downwards (you're pushing against the main spring) then use a knife tip or similar to get behind and pry out the thin retaining ring. Slowly allow the metal plug (it's spring loaded!) to come up and out of the tube. Oil will drain rapidly then. You may need to replace the rubber O-rings on the plug.
4) Remove the dust covers at the top of the sliding tube. Reach down in with knife, pry out, and remove the retainer ring.
5) Rather than removing the forks at this point, just use the outer sliding tube as its own "hammer", pulling down sharply, which will effectively remove the old seal, then the outer tube will slide right off. Then slide the 41mm ID metal washer off. Look for and remove the metal cup that's down in the bottom of the tube (into which the end of the damper rod fits).
6) Do all the cleaning of the slider tube, inside and out, that you wish to do. Put the metal cup back in, or set it in a place where you won't forget it as you put everything back together.
7) Loosen the clamp bolts (3 total) at the steering head and below the forward cowling, being careful not to let the fixed tube slide out and damage itself on the ground. Slide the fixed tube down and out, keeping its top upwards until you are ready to spill out the various inside parts.
8) Remove those inside parts, if you wish, for cleaning, and gently clean the fixed tube. Then replace all the parts. Also, there are two copper collars/bushings on the fixed tube, one lower and one upper. They should both be removed for cleaning, then replace only the lower collar.
9) Slide the fixed tube into the sliding tube, making sure that the damper rod goes into its retaining cup down in the bottom of the sliding tub. Replace the oil drain bolt and the damper rod bolt a bit more than finger tight (I found no reason to change out the copper washers).
10) Now slide the upper copper collar down the fixed tube. Slide the 41mm washer on over it. Slide your 1 & 1/4 PVC coupler down the fixed tube, followed by the reamed length of pipe, and tap the copper collar down into place using your soft hammer on the upper end of the piece of pipe. Remove both the pipe and coupler, then slide your new seal (with a tiny amount of oil on its inside) down into place (spring side of the seal is upwards). Replace the coupler and pipe, and tap the seal into place. Now, don't forget to place the retaining clip in, above the new seal. Finally replace the dust cover.
11) At this point, I found it easier to put the 610cc of 10wt (OEM is 7.5wt) fork oil in, before mounting the forks back in the bike, BUT, you can install the forks back in first, saving the headache of having to clamp your assembly with a bar clamp. Then use a longer funnel to pour the fork oil in. See photos below. Note that if you re-install the forks first, set their top ends 2mm - 3mm above the steering head, then moderately tighten the clamp bolts. Either way, the metal plugs that go into the top of the fixed tube must be re-inserted, muscled down, and the retainer clips replaced into their grooves. Replace the dust covers.
12) Before torqueing the upper clamp bolts, put the axle into its place, finger tight. That insures everything is lined up while you torque the three (six total) top-end clamp bolts to 21nM. Now replace the crossbrace and torque bolts to 10nM (please check you specs first - this value is not clear in BMW manual). Replace brake caliper to 40nM and replace cables/ brake line in their guides; ABS sensor bolt to 6nM; oil drain bolt to 9nM, and damper rod bolt to 20nM.
13) Replace the wheel and torque the axle to 80nM.
Now you should be ready for the test ride! Did I leave anything out?
