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Too much vibration - adjusting vernier iso

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Dear Wise Ones, having got my 72 750 running well I am now using more of the rev range and find a lot of high frequency vibes especially on the overrun.

It turns out I have vernier isolastics fitted (probably Mick Hemmings). Can anyone tell me how to adjust these? Weirdly I cannot find coherent instructions on what to do.on the net.

Cheers Nick

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You really do need to ascertain which vernier set-up you have on you Norton as adjusting them varies depending on the make. On one particular brand you have to wind the adjuster shut and then back it off by 2 of the peg holes but on other versions it is 4 peg holes or half a turn.

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In short, slacken off the long mounting bolts and then turn any adjuster anti-clockwise.

That said, overrun vibration on Commandos is more usually associated with primary or final drive. Any misalignment or over-tension here will occur at frequencies which the isos don't seem to deal with.

Engine vibration ought (I think) to be the same at any given rpm whether you're accelerating or slowing down.

I'd also suggest checking fuel tank mountings for tightness and to ensure that no part of the tank is contacting the frame.

It goes without saying that no part of the drive train should be bridging the rubbers and transferring vibration to the chassis. I've seen some silly things done with exhaust mounts...

 


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