Gearbox Vibration

[robc]

Afternoon all,
I've searched through past threads for this new problem my bike has developed. I've found a few threads that refer to the same/similar problem but none had a positive identification.

Last week my 97k mile 2002 GS developed a vibration which I can feel through the footpegs and seat. It happens between 60-80mph and only in 6th gear. It's a rythmic pulsating vibration - i.e. not a constant grinding type.

I've ruled out tyres and final drive bearing as the problem as the vibration goes away when I pull in the clutch. Even if I hold the engine revs at ~3.5k with the clutch pulled in the vibration is not apparent. This leads me to belive it's a problem within the gearbox. I'm hoping someone here can give me a more positive identificaiton of the problem.

I don't know if this piece of information is useful; but a month or so ago the bike suffered a gearbox input shaft failure. I had a new shaft fitted along with a complete new clutch kit. The bike ran smoothly for a couple of week until this new vibration started. It's now parked up in my garage until the problem can be identified.

I'd hate to have to pull the gearbox again as I'm still reeling from the financial pain last time.

Does anyone have a definate idea of this problem?

Regards

RobC

 

[kennyc]

got to say it sounds very similar to the symptons I had just before my FD shit itself ! for the want of a few minutes and a new seal I would check the FD bearing race as per Steptoes most excellent guide.

 

[robc]

Hi Kenny,
I'm pretty sure it's not the final drive bearing. The vibration goes away when I pull in the clutch. My 1150RT used to eat final drive bearings and that used to vibrate in every gear and when coasting in neutral. I grant you, it's a similar feeling to what my bike is experiencing at the moment except in this case it's 6th gear only.

I did have cause to remove the final drive at the weekend and it spins smoothly and silently. I have a spare seal so I'll check at the weekend anyway.

Regards

RobC