A quick ‘How To’ install the fork seals.
You can pop the old seals out with a screwdriver or something else to pry them out. Just be cautious you don’t score or damage the inside of the fork leg/lower.
First make sure the fork lowers are clean.
Then sit the fork seals flat onto the top of the fork tube. It helps if you have a large socket, or something similar to help drive them in. I happen to have a 36mm socket that fits the diameter of the seal pretty good. It might be better if it was 34 or 35mm but it still did the trick.
I placed the socket over the seal, and tapped it in with a hammer. Here is a photo of the job with the seals about half way in:
Here are the two fork lowers with the seals fully inserted:
On the /5 BMWs, there is a chrome horseshoe that acts as both a fender mount and a lower fork brace. The studs that connect the fork brace to the fork sliders are part of the slider and can potentially leak. One of mine has slowly leaked on my /5 for years and i haven’t around to fixing it yet.
For this bike rebuild, i noticed that out of the 2 sets of fork sliders (4 sliders from 2 bikes), one leg was leaking terribly due to all the dried oil residue down the front of the fork slider.As i was disassembling the second set of forks, one of those studs came out instead of the nut coming off… so i got to thinking (and got some advice from some BMW pros), i should re-seal all the studs to be safe.
The tools needed for the job are:
The original 13mm nuts.
2 13mm wrenches
a long 13mm socket would help too
channel locks or pliers
a heat gun
and some RED Locktite
Here is the fork leg with one of the studs removed:
Double nut to remove the old stud. Tighten these two nuts tightly together:
Inspect the threads of the studs. Out of the 2 sets of fork sliders, i had about 6 good studs. 2 were too rusty or bent to reuse. After inspection, i did a quick cleaning on the wire wheel to clean up the threads.
I then replaced the nuts on the longer threaded end of the studs. I pinched the middle part of the stud that is not threaded in a vice and tightened the nut as much as i could.
Then i wrapped part of the fork slider with a rag and clamped it in a vice.
I used a heat gun to heat the fork slider to get the metal to expand. I spent a good amount of time heating the legs to a very hot temperature.
I then added red locktite to the threads of the stud and inserted the stud into fork slider by using the nut and a 13mm socket to tighten it into the slider. I went as far as i could, as fast as i could before the slider cooled down.
*** But please look into the fork slider (flashlight helps) and make sure you don’t drive the stud too far into the leg where it will hit the fork tube. If the stud goes too far, it will prevent the slider from operating properly on the fork tube, or severely damage the fork tube.
When the fork slider cools down, and with the use of Locktite, it should create a nice tight seal around the stud and not leak again.
A photo diary of the internal components of a /5 BMW motorcycle fork leg.
I plan on rebuilding these forks entirely. Good thing too. The rubber is completely rotted in some spots and it has over 10 years of fork oil sitting in these legs. NASTY stuff.
I snapped these photos partly for the blog, but also for my own memory when it comes time to replace many of these parts and reassemble everything. But when you Look At This, please excuse the beat up linoleum floors in my garage.
Feel free to comment or ask any questions. I didn’t plan on this being a ‘How To’ post but more of a photo of the pieces and parts involved in the forks. But the post ends up being a bit of both…
Please note, i removed the entire fork assembly from the frame. The fork rebuild can be done while still attached to the bike. When i go through the reassembly, and mount them to the triple tree, i will have to perform a strict alignment procedure to make sure the forks are installed properly. A misaligned set of forks can cause some harmful results to the rider. I will be sure to post my realignment procedure when the time comes. In the meantime, for reassembly, please refer to Duane Ausherman’s site on fork alignment:
Also, please note that i drained all the fork oil prior to starting this procedure.
I removed the upper chrome fork cap with the BMW tool
I then removed the upper fork bolt that secures the fork leg to the top triple tree and maintains pressure on the internal fork spring. I believe it is a 36mm nut and it can often be secured very tightly. I recommend getting a 38mm socket and a breaker bar for the removal process. The BMW fork wrench is often too small and you can not get the leverage needed to get that nut loose. Before i had a 36mm socket, i remember removing these nuts extremely difficult.
I snapped the following photo so i can remember that the nut had a washer, and the size of the spring spacer. Some models do not have a washer between the nut and the triple tree. And some spring manufactures like Progressive supply a PVC piece of pipe to cut down to size for spring tension. A longer size will equal more tension. I will probably stick with the spacer that the bike has on it. It’s a nice aluminum spacer vs PVC.
The pinch nut for the lower triple tree needs to be removed and then the fork tubes should slide out from the triple tree.
The springs were taken out and the fork legs removed.
You need to grind a flat edge on either side of a 13mm socket. Then install a hex (Allen) wrench in the hole of the socket. Hold the Allen wrench in place and loosen the nut. This will separate the chrome fork tube from the lower fork leg (lower fork slider).
I really need to invest in a good circlip tool. I have bought a few and they never seem to have the correct tension for the precision needed in removing and installing circlips.
The circlip needs to be removed from the bottom of the chrome fork tube.(FigureA)
Then you need to unscrew the lower threaded ring from the base of the fork tube. I used needle nose pliers to fit into the small holes of the threaded ring. (Figure B – though the /5 ring looks different)
Here is a shot of the first stage of my fork disassembled.
I already unscrewed the threaded plug from bottom of the dampener rod.
This photo shows how to remove the upper dampener piston.
Photo of entire fork components… in order of their removal.
Close up of the lower dampener rod’s threaded plug, spring and ball.
Close up photo of the orientation and order of the upper dampener rod and the upper piston for the dampener rod.