Hi, my dad has recently purchased a BMW K75 RT 1991
motorbike and sidecar. It only says it has done 24,000 miles but I’m not
doubts!



It has a bad knocking noise between approx 1000 - 2000 revs; then goes
completely. From research; from this site and the web I have come to the
conclusion the spring needs replacing on the anti-backlash gear on out put
shaft in the engine.

I have spoken to a BMW dealer recently who was leading me to believe that it
was the out put shaft in the gearbox, although I think he is wrong. As
all the gears select perfect and with the clutch pulled in I can still hear a
slight knock.

I am considering doing the job myself I have worked on many Japanese, British
and Harley's in the past, if I could find someone cheap locally I would let
them do it due to time.

I am considering doing the work with the engine still in the frame, I
understand that I will need to remove the sump, gearbox and bell housing, I
know the engine will need to be supported as there will only be 2 bolts holding
the engine at the front of the frame and the bike will need to be stabilised
some how!
Q: Has anyone tried this? Did it work? Should I replace any other parts
while it is in bits?

Many thanks
Alf

Alf,

You are looking at a K100 site. We will help you, but also don't want to confuse you.
The K75 doesn't have the same type of output shaft. It doesn't have the bell and rivets (good thing).
Yes it could be the output shaft but from my experience I would recommend to do the job with the engine out of the frame.
Unless you tilt the bike upside down, it could be a very difficult surgery.
Removing the engine from the frame will take you only a few extra hours and believe me it will make the job easier.
FYI, here is a schematic of the K75 output shaft.


Bert