Primary Knock....help!!

Gidday, Need help please. Recently the circlip on the gearbox shaft let go causing my clutch hub to grind up against the inner chaincase.
I replaced the circlip and reassembled everything, only to hear a deep Knocking noise coming from in the case, around the clutch hub. If I take the clutch plates out, the noise goes away. I have tried a different set of plates and the noise comes back. If I pull the clutch lever in, the noises changes tone but remains.
I pulled everything apart again and all looks well. The clutch bearing seems fine as well. Its not a chain noise, nor rattle but a solid deep knock.
Any clues?. Thanks Hillbone

Check your alternator rotor. Sounds like the magnet module is loose on the center steel hub.

grandpaul said:

Check your alternator rotor. Sounds like the magnet module is loose on the center steel hub.

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+1

Sometimes tricky to detect (easy if left for a while ), but black gunge radiating out from the rotor hub can be a clue.

Also, check that the primary drive sprocket has not come loose. My primary drive sprocket came loose on the crankshaft taper once when I omitted to fit a washer under the alternator nut. The nut was tight but was bottomed on its threads and eventually the sprocket came loose. This caused the deep knock you describe. How about the primary chain itself? Are there any seized or damaged links? Are all the teeth on the sprockets in good nick?

Is the clutch hub a snug fit on the splines of the gearbox mainshaft? Does the gearbox mainshaft rotate freely and silently in neutral? I assume that the noise occurs when the 'box is in neutral. Also, when you tighten the nut on the hub, check that for some reason it hasn't bottomed on its threads (e.g. from a lot of old, solidified Loctite).

Finally, it is not advisable to use a high torque for the clutch nut because it crushes the circlip, leading to the failure you have experienced. I forget the recommended torque, but perhaps other members could confirm the figure. There is a previous post about this, and you could do a search.

Let us know what you discover.

Dave

Some good advise here thanks . I torqued the hub to 70lbs so I will check all the points you make. The interesting part is that the noise goes away when yu take the clutch plates out and leave the hub. Cheers Will report back

hillbone said:

I torqued the hub to 70lbs

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That's TOO MUCH! Disregard the torque figure given in your manual.

Torque to 40-45 ft lbs max. - or the circlip behind the clutch will probably fail again!
http://www.norvilmotorcycle.co.uk/techtalk16.htm

Bit of a long shot here, but did you put all of the shim spacers back in?

Another one, did you take the left header pipe off? If so I had a weird similar knocking which turned out to be the pipe hitting the underside of the outer primary case and it would alter depending on revs and if it was in gear or not. It only needed to be realigned and no more knock knock..

mick