Clutch Basket Wobble

[Old Cog]

Evening All

After sitting for a few months, the clutch wouldn’t separate. So I took the cover off and removed the plates. They seemed in good condition and the wear to clutch centre and basket was moderate. But (assembled again) the plates didn't seem to be moving apart evenly as the lever was pulled in. So I took them out again. Standing to the right of the bike and leaning over the saddle to hand-operate the kickstart lever, the clutch centre spins of course but surely the basket shouldn’t move at all? It wobbles!
Looking down on it from above, the vertical plane of the clutch basket body is not quite at right angles to the centre line of the clutch (push rod). The high point (furthest from the crankcase) visibly moves as the clutch CENTRE rotates. When high and low points are at three and nine o’clock or vice versa, the tilt is most obvious (viewed from above). Though the basket does not itself rotate, it wobbles like it was mounted squint on a turning shaft.

I have to move the bike in the next few days so I put it all back together again, troubled. The weather was ghastly today so I didn’t ride but I warmed the engine up and the clutch was separating fine. It seemed much the same as when I rode it around happily for a few hundred miles last summer: heavy, a little rough at the lever but perfectly usable.
But what is actually awry/out of true? Does it matter/cost a lot? So I’m still troubled.
Then I think, “Ah. Motoscrubs!”
Thanks all.

Brian

[halfpast]

What year/ model bike? Has anything been modified at all, or original?

[Jordan]

Bent gearbox input shaft?

I use a wooden wedge in the slot behind the cylinder, to put pressure on the clutch lever. It prevents plates sticking when not used.

[Nick]

Be thankful that you've never looked closely at a Triumph clutch....

[Old Cog]

D'Oh! Sorry halfpast - I typed the post then lost it all and in my hurried re-typing I forgot to mention the bike is a 250 Mk3 from 1975. Transmission all original - as fas as I know - though now I read the original basket was cast iron and the one I was handling yesterday didn't strike me as cast, though I wan't looking for such a thing.
Thanks for the tip, Jordan. I'll use that one. But your suggestion about the cause of the clutch basket wobble is a bit daunting - sounds like a total strip down of the engine and gearbox unit would be the only cure. Sheesh!
Nice one Nick. In fact, when I saw something was amiss with this I at first hoped I could sort it by turning the screws in or out to adjust the spring pressures individually, like the BSA A7 I had years ago! (Iirc the pre-unit Bonneville I owned for a while was similar.) But of course this is a whole different kettle of bananas.

Brian

[double diamond]

A bent input shaft is a possibility, but before you get to that, is the hub nut tight? Are the two bearings in the clutch basket in good condition as well as the spacers between them? Circlip grooves and bearing bores in the basket OK? Clutch basket shims/spacers assembled properly? The primary teeth on cast iron baskets can wear unevenly causing a wobble, which could have been caused by an improperly sized/installed crankshaft primary gear or an issue with the crankshaft pinion that the primary gear rides on. Steel clutch baskets were installed on 350’s and 450’s but the primary ratio wasn’t suitable for 250’s (although I have encountered 250’s with the steel primaries installed). Matt

[Bevel bob]

Check that there is some backlash between the crank gear and the basket at all points of rotation over a few engine rotations ,the amount is not relevent as long as there is no binding. My crank was out of line and had to be trued up , it was also noisy and a bit rough from this. A bent g/box shaft is a possibility. Where are you based?.

[Old Cog]

Cheers, Gents.

I haven't taken the cover off again but when I do at least now I know what to be looking for as I take it apart. Bad clutch basket bearing sounds favourite to me. Don't fancy having to get my crank trued! There's certainly something not right, but I'll go no further for now (till after replacing brake shoes ... and cables ... and fitted cut down bars ...)

Thanks again.
Brian