Strange Vibration

Try checking the transmission main shaft nut to make sure its tight.

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I thought that. Gears might still change OK as the clutch moves with the shaft but wouldn't there be issues with the engagement dogs etc? It's unusual for the mainshaft to move and stay in position as it's generally a sliding fit in the bearings. Should be easy to check though with the primary cover off, a good tug or tap either way on the clutch drum would prove it.

Keith, taped, tuged, pushed and pulled the clutch in and out and I can't feel any movement. Only the clutch bearing "wobble" movement. But no in out movement.

I will check the main shaft nut on the weekend, thanks Bruce

graeme

Thought you would have done that. We'll all be interested to see what you come up with as it has to be something major but as yet not obvious. Best of luck, hope you sort it soon.

Where the clutch cable goes, near the instection cover ? ? ? Yes, its an outer cover off job.

There could be a tight fit inside the bearing, so the nut is tight but it hasn't pulled the mainshaft enough for it to sit tight against the bearing inner race, 6 or 3 mm is a lot of difference. Is the MK3 mainshaft different in length to the Pre MK3 and a Pre MK3 mainshaft is fitted. What about if the mainshaft first gear is fitted the wrong way round, that definately gives issues with the clutch position on BSA Unit Singles.