1983 BMW R100RS Rebuild: Replace Fork Seals, Install Slider Dust Covers

When I bought the bike, the forks had both rubber fork gaiters and torn rubber fairing boots. But, I can’t turn the forks lock-to-lock as the gaiters interfere with the fairing boots. I think this is dangerous so I’m going to remove the gaiters and the fairing boots and install the black rubber cups on the fork sliders. I will wait for when I do the complete tear down of the bike to replace the fairing boots. I also replace the fork seals since I have to do all the work needed to get to them and I don’t know their condition.

You can read about how I did that work here:

The fork oil was about the color of the Mississippi river and there was a bunch of it captured by the fork gaiters, so it was well past time to replace the seals and add fresh fork oil.

Fork Seals Leaking Fork Fluid

Fork Seals Leaking Fork Fluid

I decided to leave installation of the fairing boots for when I rebuild the bike. They are very difficult to attach to the fairing holes with the fork tubes installed. I think this will go a lot easier when I have the front fairing panel off the bike and can get clear access to mount the rubber boots.

Old Fairing Fork Boot

Old Fairing Fork Boot

New Fairing Fork Boot

New Fairing Fork Boot-I’ll Install it Later

I had a very difficult time removing the fork top nuts. Someone likely used an air impact wrench to put them in. I had to get an 800 Ft-Lb wrench to break them loose. Why do people overly tighten things!!!!!

Impact Driver (800 Ft-Ibs) Needed To Remove Top Bolts

When It’s Stuck, Get a Bigger Hammer: Impact Driver (800 Ft-Ibs) Needed To Remove Top Bolts

I installed the black rubber dust seal caps with the felt dust wiper on the inside. I learned you have to keep pushing the felt and packing it into the groove until the diagonal cut ends meet. That way it keeps itself tight against the fork tube. And DON’T OIL IT. That just traps grit and dirt in the felt wiper gumming it up.

Fitting Felt Wiper Into Fork Slider Boot

Fitting Felt Wiper Into Fork Slider Boot

Felt Wiper Installed in Fork Slider Boot

Felt Wiper Installed in Fork Slider Boot

After this work was done, I rode the bike for a couple of shake down rides. It runs pretty well. There are some burned out bulbs in the clock and volt meter and the odometer isn’t working, so I will get those sorted out next. Unfortunately my attempt to fix the odometer only broke it further, so I sent it to Palo Alto Speedometer to repair my clumsy attempt. Sometimes I have to have the pros clean up my mess.  Oh well, live and learn.

8 thoughts on “1983 BMW R100RS Rebuild: Replace Fork Seals, Install Slider Dust Covers

  1. Brook – Do you have (or have you) worked on sliders that have the oRing and glued in slider bottom? I have an 83 R80 RT with this type of slider. I’ve seen a post (Digger’s Motorrad Adventures) where he replaced the oring and re-glued the slider bottom.

    I am concerned about longevity of this repair and wanted to ask you what your thoughts are on this topic.

    Jim

    • Hi Jim,

      I’m not sure I understand “glued in slider bottom”. Is that the metal plug at the bottom of the fork slider (part# 31 42 1 231 506) that the treaded end of the damper rod goes through that is secured with a nut to attach the slide to the damper rod? If so, it’s threaded and is not glued.

      I have had no experience with glue on the forks sliders.

      Best.
      Brook.

      • Hmmm… What digger explains in his post is that, on some models (like mine), the slider is actually a hollow tube. The bottom of the slider is a separate aluminum disc which slides into the slider behind and oring and is glued in by the factory with a nearly permeant adhesive. He has good photos on his post show the slider with the slider bottom removed.

        I’ve also read posts from owners who have had this adhesive fail and the disc spins when trying to loosen or tighten the bolt securing the damper rod. This, of course, creates a leak from the bottom of the slider.

        If you would you like to read the thread form Digger it’s here…

        http://www.diggersmotorradadventures.com/2020/04/fixing-r80gs-fork-leak.html

        I took some pictures of the bottom of my slider to show you but I don’t see a way to attach to this reply. They are essentially the same as digger has posted so no great loss.

        Jim

        • Jim,

          Ah, now I see. The G/S fork is the same as the one on my current R80ST project. That said, the R80RT fiche on MAX BMW shows two types of forks, the type used on the R100RS and the type used on the R80 G/S. Looks like you have the same one I have on the ST. That said, I do not plan on removing that plug.

          Best.
          Brook.

          • So you didn’t powder coat the sliders? That was my plan but doubt the o-ring or adhesive would survive the oven.

            Thanks for your input.

          • Jim,

            I have not powder coated those sliders on the R80ST as they are natural aluminum. I did have mine vapor blasted.

            If your R80RT sliders are black, you could rattle can paint them with brake caliper paint, such as provided by Dupli-Color at any auto parts store. I have painted black sliders this way in the past and they came out very nicely.

            Best.
            Brook.

            Best.
            Brook.

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