The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Bsareg on 01.09. 2018 12:39

Title: 4 spring clutch
Post by: Bsareg on 01.09. 2018 12:39
Hi, does anyone have a diagram or parts list for the alternator 4 spring clutch? Presumably, it has a cush drive within as I don't think there's room for a cush on crankshaft. I'm  trying to fit an a10 clutch to dbd34 for electric starter but crank has been modified so no cush drive. Bought a new clutch and am trying to fit a65 centre into it but there's not much for the rollers to butt upto, so I'm missing something. Cheers, Reg.
Title: Re: 4 spring clutch
Post by: JulianS on 01.09. 2018 14:01
I dont think the A65 4 spring centre hub is compatible with A10 components. The A65 bearing assembly is a different design and the plain clutch plate ears are a different shape. (first photo A65 plate on top of A10)

You can fit a complete B31/33 alternator clutch but it has one less plain and bonded plate.

You can fit a preunit 650 Triumph alternator clutch with the BSA adaptor on the mainshaft. This used to be done a lot when owners were throwing away the BSA 6 spring.

I have a number only parts list for the A10 alternator clutch, from parts bulletin 4X from December 1956.
Title: Re: 4 spring clutch
Post by: Bsareg on 01.09. 2018 14:53
Thanks for that. I'm not really sure what I've bought. It is a newly manufactored clutch sold as 4 spring a10 with a solid centre. Amongst my stash I've a a65 centre (I think) which is identical sizewise and fits the plates but seems to need a 2" od x 1.5" id washer for the rollers to bear against. Something similar to the Triumph version but smaller. It seems from your list that the genuine a10 clutch had no need of this. Looks like its a special I'm going to have to make up. Thanks for steering me on the right path. Reg
Title: Re: 4 spring clutch
Post by: Peter Gee on 20.09. 2018 22:17
Given the solid centre, you have bought the non-cush drive version of the 4 spring Triumph. The 42-3170 adapter does not require a special branze backed washer like some Triumphs. The bearings run straight from the adapter to the drum rear face.
Title: Re: 4 spring clutch
Post by: Bsareg on 21.09. 2018 21:09
Thats reassuring,  As it has the Pearson seal conversion for the starter which requires lots of oil in primary case I was thinking of giving it a go without the bronze washer but thats put my mind at ease. Thanks for that.