K-Bike Alternator Drive Rubbers

By Don Eilenberger
April 1996

Went and did the drive rubbers (we'll call them goobers for clarity) on my K100RT last night - I think the results were what I hoped for, but won't know until later today when I take it out on the road.

Approx time:

Special tools needed:

  1. Metric allen-drivers are good things to have, with 3/8" drive and 2" and 6" extensions
  2. Normal metric sockets
  3. Normal metric allen wrenches
  4. Phillips and regular screwdriver
    In addition - for lily gilding, small stainless brush
    for cleaning aluminum surfaces, sandpaper (120 grit is good)

Parts needed:

  1. Rubber drive goobers (3 needed - cost ~$2/each/US
  2. Replacement nuts or washers for any you are likely to drop.
    In addition - for lily gilding, can of Wurth Silver
    wheel spray paint. Can of black glossy spray paint.

Step 1. Remove everything in the way of the alternator

  1. Remove battery side panels
  2. Disconnect ground lead from engine
  3. Take one end of seat holder-open off - so you can open the seat a bit further (lift off seats - this doesn't apply)
  4. On right side of bike - remove pin holding computer in place.
  5. Slide computer towards left side - disconnect main connector (this is much easier than how the book tells you to do it - thanks to Corky Bessette for this tip).
  6. Remove computer
  7. Remove plastic housing computer is held in.
    *LILY GILDING - take housing to laundry room sink and
  8. Search for any of the four rubber thingies the housing sits in - they will travel to the same corner of the garage the little red tubes that come with spray cans like to hang out in.
  9. Remove battery holddown (two long phillips screws)
  10. Remove wires from positive side of battery
  11. Remove battery vent hose L fitting from battery
  12. Remove battery from frame
  13. Remove battery tray from frame (on early bikes, you must disconnect the rear brake reservoir from the battery tray - it can stay connected to the master cylinder). Four 10 mm nuts hold the tray in place
    *LILY GILDING: You can now clean up and paint the
    battery tray and the battery holddown.
  14. Move coolant overflow tank out of the way (you don't need to disconnect or drain it - but try to keep it upright more or less)
  15. Remove plastic side cover over alternator - two allens
  16. Disconnect main connection from alternator - this plug pulls straight out towards the rear of the bike (it looks a bit confusing - ask me how I know!)
  17. Remove 3 large allen bolts holding alternator in position (one is more or less hidden between alternator and starter)
  18. Pull alternator towards rear of bike and remove from bike
  19. Remove old goobers
    *LILY GILDING - at this point, you can clean everything
    in sight. I'd resist painting the alternator, but a good
    cleaning with a stiff brush is in order. Do not allow
    dirt or metal particles to get inside - this would be
    a bad thing. Also a good time to check your brush length..
    two screws on white part with transistor on it. See
    books for acceptable lengths (this part is a common
    Bosch part - used on all newer bosch alternators - it
    can be purchased from sources other than BMW moto dealers)
  20. Lightly grease new goobers (I used silicon vacuum grease - they should now last forever)

Step 2

Assembly is the reverse of above.. check the alignment of the new goobers with the 3 fin drive flange on the bike - there are cutout marks on the alternator portion to help you line it up (this isn't mentioned in any manual I've found, but was obvious to me once I tried to figure out HOW to line them up).

When done, start bike and listen to quieter engine! (at least it seemed like this to me at 12AM last night..)

Step 3

Reset clock if you have one when done.


Don Eilenberger