Greg,The only K75 that came with the “standard” Fichtel Sachs forks were the K75 C and K75T. These had 7″ of travel and (poor) dampening in both legs.Prior to 8/91 all K75Ss and K75RTs came with the Fichtel Sachs Sport forks with dampening in only the left leg and 5″ of travel. The later (89-90) Cs may have had the Sort forks
After 8/91 ALL K75s came with the Showa forks with dampening in both legs.
The Fichtel Sachs forks were 41.35mm (1.628″) in diameter with a bulbous dust cover on top of the slider.
The Showa forks were 40.95mm (1.612″) in diameter with a standard lip seal at the top of the slider.
Lee, I am starting my first dive ever into repairing/servicing the front forks and fork components on a 1987 K75S. I am desperately searching for the expertise that you obviously have with K bikes as noted by your comments on the forum.
The problem is a hands off lower speed wobble. l often checked for minor wobbles while riding at lower speeds with my hands off the bars and had NEVER experienced a wobble in the previous 34 years of ownership. After a major service, performed at my local authorized BMW dealer, I discovered the wobble on the first subsequent ride. When bringing it in with this new complaint, they never identified a cause, nor a cure.
I have scoured what I can find online with regards to this problem on the old K bikes, but there is not a ton out there. The first step was wheel bearings, which I removed and replaced with no change. The most pertinent video reference I could find was a specific 3 part series from a person named Frank that does go into detail on the problem, but the videos are very hard (for me) to follow as a reference or guide although it is very interesting with the fork alignment discussions.
I am the original owner of this K75S and bought the bike at CC Cycle Salvage in Corpus Christi TX in Sept 1986. Very early model, I think #238 (probably thanks to your research) of all K75S’s to come into US. It has never been in an accident nor a higher speed slide, and certainly no impact to the front end.
I do not have a ton of mechanical experience, but have retired, have the time, and I am building more confidence in jobs I wouldn’t have attempted in the past.
My primary manual is the Clymer I bought probably in 1989/90 as it is the 1985-1989 K75&K100 Service/Repair/Maintenance manual. My secondary reference is the Haynes that covers the K100 (2 valve) ’83-92 and the K75 ’85-96. I’m not too thrilled with either, especially the pics in the Clymer, but the Clymer definitely goes into a much greater detail.
Here are a few questions for you if you please:
Which is your favorite manual for the K75S?
I have seen the fork discussion, and others, that you have contributed your expertise. I am almost 100% positive I have the Fichtel – Sachs in the original ‘S’ configuration as my L fork has the “S” (with 3 integral dots) stamped on the slider, not near the fill cap on the tube. The right fork does not have the “S” stamp on the slider. Both of the risers have “Brembo” stamped on the slider near the brake mounts, and the fork slider serial numbers are sequential, 1 454 325 and 1 454 326.
My current issue is I am trying to remove the fork top cap, page 380 if you have the Clymer manual that I do, and I can’t compress the top cap by hand far enough with a socket/drift to remove the snap ring and start removing the internal components….to get the slider to a paint shop. I don’t think I missed a step in the manual as I’ve read it probably 20 times, so do you have any suggestions to get the slider off the fork tube?
Lastly, there seemed to be an inordinate amount of fluid in the left fork, which is the “sport” fork with the shorter travel. Any fluid in these forks was changed at a dealer, or at a guy named Stan’s shop in suburbia Philly. Stan was a hard ass, but he used to race Beemers and he was an excellent mechanic.
I am going to measure the amount of fluid after it is fully drained. If the fluid level was too high, could that be a potential cause for a wobble? Also, I am not too familiar with fork fluids, but the drained fluid looked good, not cloudy or stinky, and was a purple color. Any ideas of the brand/viscosity with that color?
Any help would be greatly appreciated! Also, more than likely this is not the last communication from me. Thanks for your time Lee, Ross V Velardi