Good Vibrations "NOT"

[Benson]

Help please.

If I ride just over 80mph in 6th I get a very fine vibration that seems to be set off by a bump in the road or a change in the surface, if I dont throttle off it get worse. I thought it was from the front end until going round a sweep (nothing too tight but the road was wet) the vibration kicked in and ended up for the next hundred yards with the rear trying to overtake the front weaving to left first then kicking in and coming over to the left. Had a 400 mile run on it and can basically get it to go into this vibration mode on command.

Conditions are. 6th 82mph plus, everything has to be warmed up (does not do it from cold) and any slight bump in the road. to stop it throttle off and it settles.

The Bike is standard 1200 gs with Wilbers, where do I start to look?

 

[oblertone]

I'm no expert ...

... but as the condition appears dependent on things being 'warm' then it'd seem sensible to start with the things that warm up during a ride i.e. tyres and their pressures. For example, I had 'issues' with a pair of Anakee 2's that were just not right; turned out that a very small variation in pressure (+/- 2psi) cured the issue.

 

[Benson]

CHecked tyres they are the same and the presure was fine, they are slightly flat in the centre from M-way riding but it seems ok. I was wondering if it could be the final drive, I can only get it to do it in 6th revs are about 4.2K.

 

[Deleted account 211025001]

Have you checked for play in the FS/back wheel?

Given what you say, prob worth checking 'after' a run - get the bike on the centre stand and grab the wheel top and bottom. Try and rock it from side to side, around the axle.
Whilst there is supposed to be a tollerance for a min amount of play you shouldn't be able to feel any - if it rocks/knocks there is an issue with the FD.

Andres

 

[mr badger]

CHecked tyres they are the same and the presure was fine, they are slightly flat in the centre from M-way riding but it seems ok. I was wondering if it could be the final drive, I can only get it to do it in 6th revs are about 4.2K.

Could be an imperfection in the tyre - slightly out of round maybe?

have you checked the balance? Easy on front but you'll need to take the back off to test it.