AMC - Clutch

OEW591 · Post by **OEW591** » Fri Apr 24, 2009 9:30 pm

"all this would seem to start from the clutch push rod but I can't see how unless someone has done something daft like fit an alumiiniun one which expands." - this was my first thought and I bought the correct rod from JSL but surely an expanding pushrod would lessen the free play and cause slip rather than drag? It is as if the mainshaft is expanding!

Don, I have checked all the parts and they are correct. I have used two pressure plates - the original one that is slightly thicker than my G12 CSR type clutch and a deep one, which I assume is for the 3-plate type but the same symptoms exist whichever one I use.I have even contemplated converting to the later CSR clutch but I really don't think the problem is to do with basket, rod, centre or plates.
The handlebar lever is 7/8 fulcrum and the cable is new (and lubricated).

As an aside this bike developed a knocking soon after I bought it which turned out to be a loose conrod cap, a previous owner had used ordinary nuts on the studs and these had come loose. I'm beginning to wonder if he bodged something in the gearbox as well.

itma · Post by **itma** » Fri Apr 24, 2009 10:10 pm

"but surely an expanding pushrod would lessen the free play and cause slip rather than drag? "

of course it would, old age creeps on.

probably your answer lies in the last sentence.
If you find more than two bodges, time to worry, the ball in the pushrod trick is the other.

There is somewhere here info about mixed up mainshafts and clutch hubs,something about the shaft/shoulder measurements.
might be worth looking at, I am also thinking loose bearings somewhere.
Time to get the box out I reckon.
You seem to have covered all the other options quite sensibly.
I cant recall exactly, almost senile it seems

SPRIDDLER · Post by **SPRIDDLER** » Fri Apr 24, 2009 10:23 pm

Alan, it's not completely clear from your postings and it is relevant to know (since i'm pondering various scenari) whether the problem pre-existed or started only after you fitted all the new bits...
Reading between the lines it appears that the replacement friction plates have bonded friction material rather than corks. Is that correct?
IMHO and thinking aloud, something's swelling/expanding when warm or hot (clutches don't normally get/stay very hot in everyday riding though). E.G. assuming you have 5 friction plates each one only has to swell 1/20th of an inch (x5 plates = 5/20ths or 1/4") freeing up that amount of slack in the cable - but the new JSL plates 'shouldn't' swell at all. Should they?

Duncan · Post by **Duncan** » Sat Apr 25, 2009 12:51 am

Based on all that you have done, I would agree with Ken and start to suspect the gearbox (assuming as Neville notes that it not something that you originally changed).

It would have to be around the mainshaft either the end nut under the clutch operating mechanism, the mechanism its self moving or possibly the bearings moving.

Another off the wall thought is the control cable clear of the exhaust and cylinder head, is the nipple firmly seated in the lever, on a roll with this one now how about the outer spiral cable compressing with use setting up more free play, do you have a spare cable to try?

OEW591 · Post by **OEW591** » Sat Apr 25, 2009 9:09 am

The problem has always been present, I have replaced all the obvious parts (plain plates,friction plates, cush rubbers, pushrod, nut and spring washer, and the cable) in an attempt to cure it but the problem always returns.
The friction plates are the surflex type from JSL.

I think I have no alternative but to investigate the gearbox. I am no expert but I've had both Burman and AMC clutches completely dismantled before and never had a problem like this so I'm pretty sure the fault is not in the clutch, plus the fact that it pre-existed before I took it apart.

Many thanks for your replies. I'll report back once I summon the courage to take the 'box apart.

rgregory · Post by **rgregory** » Sat Apr 25, 2009 3:16 pm

Maybe the mainshaft has end play when hot.

Perhaps a bronze bush from a housing (or even inside a gear) is loose when warm but binds up when cold to make it seem like no end play.

Hopefully not a crack between the shaft ball bearings causing them to move a bit ?

Good luck,

Rob

OEW591 · Post by **OEW591** » Mon Jul 06, 2009 6:47 pm

Well, what a can of worms this bike is turning out to be.
There were two possible causes for the cable free play "creeping". Firstly the oil seal on the large mainshaft bearing had disintegrated and the "garter" had fallen between the gearbox shell and the bearing. Therefore the bearing must have been mobile. The outer edge (inside the box) had also been chewed by the nearest gear wheel.
I thought this would cure my problems but no, on reassembling the clutch I couldn't get any free play between the back of the clutch centre and the inner chaincase. This turned out to be a very worn clutch spider allowing it to go too deep on the mainshaft splines. A new one gave a clearance of 1/8 inch - joy.
I've now ridden it for fifty miles and no cable free play creeping or nasty grinding sounds from the chaincase.
Thanks for all your suggestions and special thanks to John Bolton for helping me out with the tricky bits.