There is a rattling noise coming from the gearbox area on my K100RT when it is cold, once the engine warms there is no noise. The bike performs nicely with no vibration other than what I would think is normal. I have replaced the rubber cushions in the alternator drive coupling which were pretty worn and the noise is still there. I mentioned this to k75cster and he said it is probably the output shaft rivets coming loose as this is a common problem on early bikes that only have six rivets the later bikes having twelve. There is about 40mm backlash when you move the rear wheel back and forward with it in gear. What is needed parts wise to convert to the later set-up and which model bikes would have the upgraded parts?

Steve the movement at the rear wheel is well within normal in fact very good.
It sounds like the rivets may be loose. Alby had a thread here about him fixing the rivets but I am not sure if it was finished.
Try this link http://k100rt.aforumfree.com/t3750-output-shaft-rivet-repair-lets-get-serious

Hi Rick,
Thanks for your reply, the link was very interesting. The reason I asked about the models which have the upgraded parts is I know where there is a 1100LT engine and transmission that I can buy if it has the parts I need. I think the engine has a bad cylinder which is strange as it only had 39,000kms on it when it stopped.

i think he still has the rattle and an exploratory surgery is to be performed soon

he has replaced the out side roller bearing in the alternator drive coupling shaft ...some while ago with positive results ....but we are thinking that it may have caused some more wear on the inboard side of that sprag clutch idler assembly . and the needle rollers on that shaft as well ...stay tuned for updates from our eager friend .

cheers alby !!

The 12 rivet shaft was first used on K100RS4V (-90), later fitted on all other models.

You can check your rivets by undoing the right engine cover and swing it out at the rear.
Watch the rivets while turning the rear wheel forth and back (in gear).

Your noise could also be caused by worn tension mechanism at the rear of the "drum" with the rivets.
This is a narrow toothwheel and big circlip at the rear of the bigger toothwheel.

What does that toothwheel actually do? I will remove that cover and have a look and see if there is any play in the rivets.

STEVE1959 wrote:What does that toothwheel actually do?

Taking up the play between the toothwheels.
Here you see a picture of a worn circlip in that mechanism, from CF`s rebuild page.
The rebuild page you find here.

Control/reduction of backlash and the associated noise when it occurs.