Clutch wobble

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Dec 5, 2005
Another question please.

The clutch basket has a visable wooble, but when measures it is 1/16th of an inch. I note in the Norton litterature from the Inoc that up to 3/16th " is tolerable. I suspect the gearbox mainshaft has a slight bend on the outboard clutch end.
Is it a new mainshaft, or will a judicious straightening in a press between vee blocks, with a dial guage check be OK.

Cheers Richard
As to whether you can "safely" straighten a main shaft...I'd be hesitant because it is hardened and that means to an extent, brittle...but that's just gut feeling, and my gut has been wrong too. Wait for the big guys to answer that.

I just wanted to point out that the bearing in the middle of the clutch basket is, at least on mine, not of a high enough tolerance to remove all play that the basket may have when mounted. I mean, the basket is somewhat loose, you can wiggle it, even with a new bearing installed. Are you sure the main shaft really has a bend, or is this just the bearing?

Make sure it isn't just a replacable bearing before doing the deed on the shaft... :wink:
main shaft straightening

Hi Richard,
I too had a clutch wobble I noticed while installing my belt drive last winter. It was bad enough to motivate me to do something about it, so, out came the main shaft. With alot of patience, hardwood blocks, dial indicator, and hydraulic press I straightened to dead on no deflection. While certainly an improvement there was as Hewho suggested a certain amount of wobble in the clutch basket it self.
But, to answer your question, yes, the mainshaft is straightenable, and seeing that you are heading into your winter season might just as well take the time and make sure all is well.

justa thought,
Mainshaft is surface hardened with a softer ductile core, you can get it bent straight mounted in a lathe and clocked with a DTI.
I wonder if the wobble isn't due to the fact that that large basket is supported by a very small snap ring. Mine has always wobbled.
Whether your shaft can be successfully straightened depends on how far it is bent, even if it is only case hardened the molecular structure has already been subject to stresses and loads and straightening it only exerts more stresses, if the material is stressed beyond it's elastic limit it will eventually fail, if it is bent towards the end of the shaft, rather than the middle, it will be even harder to straighten.
Might not even be a bent mainshaft. Could be something else, such as a worn bearing. My clutch had a bad wobble - turned out the locating circlip and washer were both *missing*. DPO had been in there and didn't bother to replace them (he didn't like replacing small parts :roll: ).

Fitting a new circlip and spacer fixed my wobbly clutch.


That's what I meant. Even after replacing the circlip, mine has a wobble and the main shaft is straight. Just not much support for the clutch basket with this design. Let i wobble.
We always buy those little snap rings three at a time. You need them in stock if you have a Commando.
the shaft os bent

Thanx all for your answers, the feed back I can offer on the clutch wobble is that the shaft is indeed bent. The bend is right in the centre and measures .3mm (12 thou roughly). So the press at work is going to give it a gentle nudge this week-end.
I wonder how the shaft got bent in the first place. The bike has not travelled a great distance (14,000 miles) so what kind of abuse causes a bent mainshaft. The rest of the box looks quite OK.
Or is some of the common clutch basket wobble associated with wonky mainshafts. Does the shaft distort during heat treatment?

The AMC transmission was designed for 350-500cc singles and has worked remarkably well behind the 750-850 Nortons. It doesn't however, like to be abused. When we were kids we would try WOT clutchless shifts, (hit the kill button and bang the shifter). This often resulted in bent mainshafts, layshafts, broken gear teeth, etc. on transmissions with much less than 14,000 miles!
Also when the layshaft bearing and/or kickstart bushing starts to wear, the mainshaft and layshaft are no longer parallel and it becomes more difficult to select the next gear. This can also result in a bent shaft.
Check the layshaft for straightness also and replace the bearings and bushing if there is any doubt of their integrity.
Shaft now straight

Thanx for info Ron, you Americans must have caned those poor old things, u can guess that my bike is ex USA, Minnasota I think, but now living peacefully in Sydney, Australia.
I have check layshaft, and it is fine between centres in the lathe. And the Portuguese bearing in the lay has been replace by a rolled with the endfloat in check at the kick start end.
I have just straightened the mainshaft in a press, so will see how it looks in the gearbox this afternoon, hopefully the clutch basket wobble is greatly reduced.

Cheers Richard
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