Vibration woes again

[Davew]

Once again I'm having vibe issues with the bike after sorting it a while back.  I was getting a lot of vibes through the fuel tank. I discovered that when the small bolt at the front of the tank was removed, all my vibrations went away. I've been trying since to figure out why this is and replaced the front tank mount with no joy. I also drilled a slot out of an old mount to let the tank slide forward slightly (which seems to be where it wants to sit). This seemed to help but as soon as I tightened it up fully, the vibes were back. 

I'm at a loss, as I can't ride around without the front tank bolt attached but don't want to have to put up with the vibes it creates when it's on!  Any ideas??

[Doddsie]

Tried a rubber washer?

[Davew]

Yep. With no joy, still got vibes. The tank seems to be the thing creating the vibrations somehow, there's no real increased vibrations where it bolts on. Maybe I should try getting a cheap old tank and see if it stops.

[Doddsie]

Youve got the tank rubbers on the frame I presume?

[Davew]

Yeah everything is in the correct place and I've swapped out front and rear tank rubbers and brackets in case they were bent

[reddave101]

Have you checked the bracket under the tank that the fuel pump attatches too?? It may not be the tank? When you are tightening it down, the bracket underneath may be the thing vibrating and if it's touching the tank, it will vibrate through it?

[Davew]

All the fuel pump etc seems fine with no vibrations.  The tank isn't really being pressed down any more when I'm doing up the front bolt as it's already sat on the tank rubbers, it just seems to act as a resonator for any vibration going through the frame when the front and back bolts are tightened.

[JoeRock]

Why not just get a slightly longer bolt, double rubber washer it, and not tighten it all the way down? Tank will still be attached, just won't be clamped down as firmly as normal, and shouldn't vibrate?

[Davew]

Why not just get a slightly longer bolt, double rubber washer it, and not tighten it all the way down? Tank will still be attached, just won't be clamped down as firmly as normal, and shouldn't vibrate?

yeah I just tried a rubber washer again this morning which did make a bit of difference.  might try the combination of that and my drilled out tank bracket.  so frustrating trying to figure it out!!

[darrsi]

I'd look for any wear and tear caused by vibration on paint under the tank, it may pinpoint somewhere else.

[Davew]

I'd look for any wear and tear caused by vibration on paint under the tank, it may pinpoint somewhere else.

A good tip, cheers.  I had a look but couldn't see any marks other than down by the seat where the loom passes under the tank.  Pretty sure this is normal as you'd have to remove the whole loom to re route it.


I might try moving the tank rubbers further down the frame, see if that makes any difference.  Seems like it want to be able to slide forward more than the front bolt lets it, but even drilling out the hole hasn't made any difference.  it's very bizarre. 


I think the tank is resonating when it's bolted down rather than any vibrations transferring to it.  There's a rubber cover under the tank where the electrical connectors attach, but it doesn't seem to fit properly, not sure if something is missing there.  will endevour to upload a pic.