Oh, and I own a few K75s. It is a medical condition known as K pox.
Dave, I think I may also have a case of K-pox, I already own two K100RS bikes, one of which was in running order when I bought it, in fact my Younger brother rode it 1,000 odd KM to where I was supposed to pick it up a week of so after he left it. Sadly that didn't happen so by the time I did get it home on a truck, it was a non-runner. A pity because I wanted to use its electrics and engine to get my other one running, it is a beauty as it was parked up under hessian bags when it was only a few months old in the late 80s and there it sat untilthe parents of the owner began to make preparations to go to a retirement home. It looks immaculate, sadly though the rats got into the wiring and nested above the engine causing an amazing amount of damage, hence my intention to do an engine swap.
Today I have accepted custody of another non-runner, this one has been in the hands of someone I know for nearly 10 years, it has an interesting fault - connect a battery and turn on the ignition and it blows the hall effect transistors to smithereens. Over the years he has had a number of attempts to correct this, including the most recent one yesterday. He rang me to say "take this piece of $hit away please".
So yes, I think I have K-pox.
Which brings me to the point of this post.
My Haynes manual only covers the models 1983~1987 and I do note it is probably brimming with Mr Haynes' usual typos, inaccuracies and other nonsense (more on this in the next post).
According to my manual K75 and K100 forks have the following metrics:-
Travel
K75S and any model with "S" suspension - 135mm
All other models - 185mm
Stanchion OD - 41.325 ~ 41.350mm
Lower Leg ID - 41.400 ~ 41.439mm
Fork Oil capacity
K75S and any other model with "S" suspension - 280cc
K100 and all other K75 models - 330cc
K100RS/RT/LT - 360cc
Recommended fork fluid
A bloody long list which includes the following fluids that I know the characteristics of - BP Aero Hydraulic, Shell Aero Fluid 4, Spectro SAE10 (for competition use only supposedly).
Given that these things are so very similar to R65 forks internally I am goign to start with a 50/50 mix of Castrol Fork 5 and Fork 10, I will be very surprised if that isn't in the ball park. For someone who weighs less than my 130kg I'd start with 100% Fork 5 and see if that suits.
And lastly.
I changed the wheel bearings and wasn't that a revelation. After years of performing strange acts and mouthing incantations to change airhead wheel bearings, the K-bike front bearings were a revelation.
Sealed ball bearings with an internal spacer. It took me all of ten minutes to change both bearings (luckily I own a set of expanding blind bearing pullers). So quick and simple I found myself in disbelief that BMW would stoop to doing something the easy way.
Yes, they will not last the moon-and-back-several-times distances that the Airhead wheel bearings last, but 10 minutes too swap out bearings is hard to beat.
Of course Mr Haynes made note of the fact that you are supposed to heat the wheel before basing bearings out or in. I decided to give them a love-tap and see what happened before putting on the thinking cap to work out how to uniformly heat something of that size to 100 degrees centigrade. Fortunately both bearings came out easily and there was no damage to bearing bores. I do know about the requirement to heat early airhead hubs, but this is a far more massive casting.
So, got to look at a friend's bike that is making funny noises and if I get home early enough, I might assemble the K-100 forks.
