Replacing the fork seals or dust seals on an R1150 is pretty easy, and should only take 10-15 minutes. This is how I did it on my 2001 BMW R1150GS without removing the front wheel or forks from the motorcycle.
Tools I used:
The new dust seals on the left and the oil seals on the right. I paid about $15 for each seal on bikebandit.com.
This is the order of all the parts in the fork tube on the bottom, left to right: washer, oil seal, retaining clip, dust seal, *not shown fork nut 14mm*, fork cap
1) put the bike on the center stand to make the front wheel easy to move around.
2) Remove the re-usable ziptie holding the brake or clutch cable depending on which side.
Press the tab back towards it to pull it apart.
3) Remove the cap on the top of the fork with the flat blade screwdriver by inserting it into the slot
4) Using the 14mm socket and 22mm wrench, remove the nut on the top of the fork tube. I used a 7/8” as shown below.
5) Push the fork slider into the stanchion and then pull it out. The front wheel will freely move side to side to make this very easy.
Have a rag handy as the slider will likely drip fork oil as you pull it out. Wipe it clean, and set it aside in a safe place where it won’t be scratched.
6) Use the flat blade screwdriver again and remove the dust seal on the top of the stanchion.
Both of mine were split and cracked (and leaking). I’d recommend replacing them along with the oil seals.
8) With the needle nose pliers, pull out the retaining clip
9) With the seal puller, remove the oil seal.
If you don’t have a seal puller, get one. It makes this part take five seconds (literally) with no damage to the fork tube versus trying to lever (and bend) with a screwdriver or something else. I bent two different screwdrivers, but didn't get the seal out. I've also read you could screw wood-screws into the bad seal and pull it out with a pliers. The seal puller did the job for me.
the leaky oil seal aka fork seal
position under the fork seal
pull up slightly and it will pop right out
remove the seal
the damage to mine is clear here:
new fork seal aka oil seal below:
this is the top view:
this is the bottom view:
10) seat the new seal with a socket. A little fork oil on the seal makes it easy to start by hand. Make sure to insert it with the bottom side down.
Get a socket that is the same diameter as the outside of the oil seal, and that fits inside of the tube. You want to push on the hard outside, not the soft inside of the seal. I used a 3/4” to 1” impact adapter I found at harbor freight. A 34mm or 1 3/8” socket might also work.
Put an extension on it and pound it home.
11) reinstall the retaining clip
12) install the new dust seal by pressing it into place
13) use the 3mm allen wrench and remove the little bleed screw near top of the fork slider
be careful not to lose or damage the tiny o-ring
14) push the slider all the way into the fork tube and then pull it back up to the top yolk in its final position. Air should rush out the bleed hole. I repeated this twice.
15) replace the bleed screw and hand tighten until snug. This is a small screw, so be careful not to over tighten.
16) Replace the nut. Using the 14mm socket and 22mm wrench tighten. If using a torque wrench, tighten to 45Nm.
17) Replace the top cap and re-usable ziptie.
18) Repeat on the other side.
19) Go for a ride!
If you want to also replace the fork oil, use BMW fork oil grade 7.5 and put 15.8 oz. of fluid in each fork.
Other R1150GS Guides:
