Heavy AMC clutch

[Anders Welle]

Recommissioned this spring, my 1961 Model 31 has a really heavy clutch. I have to avoid urban roads. It's 40 years since I had this apart but teardown has not revealed any obvious cause apart from a somewhat notched clutch centre which I intend to replace. This should not cause heavy operation at standstill however.
Clutch type is AMC 5-plate consisting of 4 steel plates, 4 double sided and 1 single sided friction plate. Handlebar lever is 7/8, cable is Venhill teflon and clutch pushrod operates smoothly.
The only deviation from stock are springs which on inspection seems to be the earlier 4-plate springs, being 2,6mm in coil thickness.
I suspected wrong springs so I ordered both early and late types from the Club, and have tried installing both. The later 3,0mm springs which should be correct for my clutch makes the plot even heavier and causes wrist ache after only a few pulls. The lever operates smoothly but oh so heavy.
Adjustment of spring nuts is flush with studs, and 1/2 turn slack on the center screw. The sprocket and back plate are of the correct late type. I understand that the clutch centre and spring studs are identical between the 2 clutch types so can not be suspected.
My bike is a bitsa of Model 30 and 31 parts, and there may be parts from a Norton 88 I owned, at least in the transmission. I intend to have a close look at the operating cam in the gearbox, but otherwise i am at a loss. Do you have any suggestions?

[dave16mct]

When you say the lever is 7/8" do you mean centre of nipple to centre of pivot? This is essential for a light action. Have you lined the cam properly in the gearbox with the cable entry? I'm not sure what you mean by early and later springs. The springs you need are the AMC standard type. Not CSR, which sounds like the ones you have. You have to adjust them by the book, then you may have to unscrew them slightly until the action feels OK but doesn't slip. It's a real pain to do especially on an alternator bike. You could always fit the easy clutch mod drawn by Alan Maines (do a search). I have just bought the bike he did it on. I'll post a pic later.
Dave.

[Groily]

Is it this one Dave, 'Clutch Lore' from 2001 in Tech Articles? (I think it's not as no pix)

https://www.jampot.com/article_read.asp?id=55

Biggest things, on the various AMC clutches I've got or have had (all of which have had the 'heavy' problem at one time or another), are
* no tight bends on cable, even if that means not using the hole in the top yoke nor tying it tightly to the top frame rail
* careful alignment of the lever mechanism at the gearbox, burr-free, and a greased, straight, pushrod
* setting spring pressure so that there's no slip on the kickstart (obviously!) - but not a lot more than that - with an even lift
* and the 7/8th centres thing.

My current position is that the clutch on my M31 is only a fraction heavier than the Burman on my M20 (which is light and smooth), and both of them are lighter than the diaphragm clutch / belt drive set-up on my 650SS Notrun.

[dave16mct]

That's helpful but I meant this:
http://archives.jampot.dk/technical/Tra ... Jampot.pdf
Dave.

[Groily]

Thanks!
I was looking for that for another discussion not very long ago and couldn't find - but I remember it now. Shall try not to lose it!

[dave16mct]

Here's the pics:

Dave

[dave16mct]

[dave16mct]

[Joker_Bones]

I have a couple of AMC clutches assembled from spares, there were differences between some parts...
The pressure plate from a four plate clutch is a different depth to a five plate one.
Not all of the clutch spring studs I have are the same length, some about 3/16" shorter than others.
Different thicknesses of both friction and plain plates.
If you mix and and match the above parts and set the clutch spring nut in the same place say flush with end of the stud you get very different spring pressures.
Perhaps you have a mismatch of parts and the springs are over compressed?
assuming all else is well... Have you tried just slackening off the springs till the lever is not too heavy?

[griffin]

That's helpful but I meant this:
http://archives.jampot.dk/technical/Tra ... Jampot.pdf
Dave.

I have one of these if anyone would like it. It is minus the angle iron portion though. Private message me .