G12 clutch

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Columbo John
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G12 clutch

Post by Columbo John »

Did this look right? My clutch is very, very heavy yet still slips. The bike is 1961 G12CSR which should have 4 double sided friction plates and 1 single sided. I'm 'fairly' certain I've got all the right components but the combination of how it looks and how it feels makes me think that something isn't right.
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Groily
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Re: G12 clutch

Post by Groily »

I'm guessing the hassle is with the pushrod length or actuating mechanism at timing side. The adjuster is well out, the springs are under-tensioned by looks of. So no or too little rod movement against a pressure plate short of pressure = very heavy and slips. Suggest look at things from end to end and also just check cable is free moving too. When 'right' it should be a pleasant enough thing, especially with correct lever centres at 'bars.
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Joker_Bones
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Re: G12 clutch

Post by Joker_Bones »

You say "should have 4 double sided friction plates and 1 single sided"
Unless my eyes deceive me, you have plate(s) missing.
Appears room in the basket for more plate(s).
The plates in the AMC clutch changed around 1960. After that the friction plates have internal dogs, the plain plates have external dogs.
For a post '60 clutch the plate under the pressure plate should be the single sided friction plate with internal dogs.
Columbo John
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Re: G12 clutch

Post by Columbo John »

Groily wrote: Sun Feb 12, 2023 10:09 am I'm guessing the hassle is with the pushrod length or actuating mechanism at timing side. The adjuster is well out, the springs are under-tensioned by looks of. So no or too little rod movement against a pressure plate short of pressure = very heavy and slips. Suggest look at things from end to end and also just check cable is free moving too. When 'right' it should be a pleasant enough thing, especially with correct lever centres at 'bars.
Thanks for your input, that's certainly given me some ideas of things to check. :thumbup:
Columbo John
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Re: G12 clutch

Post by Columbo John »

Joker_Bones wrote: Sun Feb 12, 2023 11:42 am You say "should have 4 double sided friction plates and 1 single sided"
Unless my eyes deceive me, you have plate(s) missing.
Appears room in the basket for more plate(s).
The plates in the AMC clutch changed around 1960. After that the friction plates have internal dogs, the plain plates have external dogs.
For a post '60 clutch the plate under the pressure plate should be the single sided friction plate with internal dogs.
I have 4 double sided plates and 1 single sided in the basket as per the parts list for my model and year. But....... as you say, there appears to be room in the clutch basket for more plates.

Are you saying the outermost plate should be single sided?
Groily
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Re: G12 clutch

Post by Groily »

After reading JB' s comment I blew up the pic, and I agree the stack isn't filling the basket. Which affects everything!
The inside / outside tang thing can be got round as long as all friction and all plains match - but it is also a common problem if there's a mix.
I think this is a 'start again' job on the basket, plates, pushrod and operating mechanism. The lever at the cable end needs to align 100% with it's notch - there's a tool for that but it can be checked etc and set by eye usually.
Steven S
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Re: G12 clutch

Post by Steven S »

If you check the spares lists, you'll see that the same basket, centre and pushrod are used for the 3, 4 and 5 plate variants (not counting the single-sided plate). The number of plates fitted was determined by the pressure plate which is why you'll see variations in those. So theoretically any 1960-on clutch can be 'upgraded' with a change of pressure plate. Yours looks to be the right one.
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Joker_Bones
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Re: G12 clutch

Post by Joker_Bones »

2_e_clutch.jpg
16. is the single sided friction plate, friction surface facing inwards.
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Yves.Astein
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Re: G12 clutch

Post by Yves.Astein »

This is how mine looks disabled and fully assembled. I started with a slipping clutch when I got it. New plates fixed it. Yours looks to me as if something is missing. The clutch spring screws are not adjusted in my last picture. They usually need 2 turns out after they have been screwed in flush. At least mine do.
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