I've got a weird noise on my k100 I'm wondeing if someone can help point me in some direction on getting it sorted. Basically had a short ride today 3 miles get some brake fluid all fine. Then on the way back this noise started. I'd recently replaced the shaft so have pulled that to see if it was the problem but the shaft is still fine.

The bike will accelerate fine and go through all the gears fine however just get this horrible and worrying noise. Its my only form of transport until my other k100rs is on the road (input shaft seal failure).

Anyone able to possibly point me in any direction to get it sorted ?

TheJoker wrote:The bike will accelerate fine and go through all the gears fine however just get this horrible and worrying noise.

Anyone able to possibly point me in any direction to get it sorted ?

Does this noise only occur with the clutch lever out? Does the pitch of the noise get higher when the throttle is twisted?

Starter motor not disengaging.... sprag clutch??

@laitch noise occurs with the clutch in or out. And yes more throttle equals a louder noise.

I couldn't hear the noise but....

On centre stand with engine running put in gear and go up through the gears and keeps revs constant without altering the engine speed [use 'choke'] does the noise change as you change gear?:

If yes then it's in transmission somewhere after the gear you are in, ie towards final drive.

If no then its engine related or input into the gearbox, likely culprits are clutch, clutch release bearing, alternator monkey nuts, timing chain related. Test revving engine then to see it is changing with engine speed.

Pull clutch in does it change: if no then it's something rotating at engine speed, alternator monkey nuts, timing chain related.

If yes probably clutch release bearing.

I like an alternator bearing as the source of this. Put the tip of a screwdriver on the alternator body and  your ear to the handle. If it's one of them, you'll know it. 

At least it doesn't seem to be spline failure, from your description anyway.

From where you are pulling the alternator would be an easy call.......most likely cause too.

It's a bit late but for anyone that sees this thread in the future found the problem. The bolt was missing from the centre as you can see from the image below.

K has been fine since but is now off the road for some work.

It's never too late to post a solution.

TheJoker wrote:It's a bit late but for anyone that sees this thread in the future found the problem. The bolt was missing from the centre as you can see from the image below.

K has been fine since but is now off the road for some work.

Aaaahhello stranger ! so I take it that missing Alternator drive bolt pulls in the sprag on the other side of that casing & that was why it was making that god awful noise as i guess it was not running secure and in the right plain. Still good you posted the find though ...well done , I'll put that in the memory bank now  . Cheers Lee

I just took a good look at the photo and it looks like the splines are getting beat up and are a bit of a sloopy fit.  It may just be the angle of the photo, but a couple years ago I had the splines on the dog strip out when that bolt loosened up.