Author Topic: Preferred SR clutch set-up  (Read 1370 times)

Offline Housewiz

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Preferred SR clutch set-up
« on: 24.10. 2012 02:39 »
My trusty BSA Spares book shows both 4 & 6 spring clutches - depending on motor serial#'s.  Since mine is missing along with the chain, what is the preferred clutch set-up - 4 or 6 spring?  And are all the parts interchangeable?  The cush drive looks like it came loose and partially ate thru the outside cover, is that any indication other than not tightening the nut enough?

Thanks as always,

Steve

Online muskrat

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Re: Preferred SR clutch set-up
« Reply #1 on: 24.10. 2012 10:01 »
G'day Steve, I think the 4 spring is much better. You will need the whole kit. The cush drive is same. The nut is to be done up FT (about 60 lbs), if it comes loose you not only do damage to the cover but can also destroy the crank shims behind the main bearing. *eek*
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Offline Motoanimal

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Re: Preferred SR clutch set-up
« Reply #2 on: 24.10. 2012 11:07 »
Steve,
I 'second' Muscrat. The 6 spring clutch was a disaster, all pressed steel (lead I think, it was so soft!) and usually self destructed if it ever stopped dragging.....

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Offline LJ.

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Re: Preferred SR clutch set-up
« Reply #3 on: 24.10. 2012 11:34 »
I agree with the four spring choice as being the most preferred, it is also the easiest to set up as well. I have had my fair share of tears with the six spring. The six spring 'can' be good if you have all new "Quality made parts"! and tons of patience.

*and welcome to the forum Motoanimal.  *smile*
Ride Safely Lads! LJ.
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1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline Motoanimal

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Re: Preferred SR clutch set-up
« Reply #4 on: 24.10. 2012 12:23 »
Thanks for the warm welcome guys!  ;)

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Online cyclobutch

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Re: Preferred SR clutch set-up
« Reply #5 on: 26.10. 2012 13:56 »
I have it on my list to swap out my six spring but it does kind of work. Enough so that given the length of said list it will probably not get to the top for the second Winter running.
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Offline minibsa

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Re: Preferred SR clutch set-up
« Reply #6 on: 16.11. 2012 04:30 »
 *idea*  dont forget the tab washer on the cush drive and there should be a hole at the end of the crankshaft for a split pin to make sure the cush drive nut stays on the shaft IF it comes loose!!!

Offline tombeau

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Re: Preferred SR clutch set-up
« Reply #7 on: 16.11. 2012 06:55 »
If you need to replace everything on the primary drive, it might be worth considering duplex chain, or even triplex primary drive and later A65/Triumph 3 spring clutch. You need an adaptor on the gearbox shaft (readily available) and you need a nut/spacer made up to replace the big spring and cams on the end of the crank.
Cheers,
iain

Offline Housewiz

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Re: Preferred SR clutch set-up
« Reply #8 on: 16.11. 2012 22:24 »
Ian,

Interesting idea.  Yes, just about everything inside the chain case cover was missing - even the chain adjuster.   The cush drive parts are intact however it appears the nut came loose and ate through the cover.

Where would I find the gearbox shaft adapter and what years BSA & Triumph had the 3-spring clutch?  Same questions apply to locating both dual and triple clutch/chain/crank sprocket parts - is there a preference for the dual or triple chain/sprocket set-up?

Eliminating the stock cush drive delivers acceptable performance/reliability?

Thanks,

Steve

Offline tombeau

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Re: Preferred SR clutch set-up
« Reply #9 on: 16.11. 2012 23:21 »
Hi Steve,
 I believe chain adjusters are only fitted to semi-unit plunger motors, on swing arm models you move the gearbox back to take up slack...then move the wheel back.
Those are A65 components on mine which are triplex. I think A65s utilsed the the clutch gearbox adapter too (cant remember, but it is a standard BSA part).
I understand that plungers had duplex....any other backwards step for BSA?
The a65 clutch centre has rubber cushdrive blocks fitted inside a metal web.
I have heard it suggested that duplex would be more efficient than triplex as less energy is lost, and also that the wider sprocket and chain hanging further out from the crank will exert greater force on my crank...but it seems to work. Also A65/Triumph bits are fairly readily available.
Cheers,
Iain

Offline tombeau

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Re: Preferred SR clutch set-up
« Reply #10 on: 16.11. 2012 23:24 »
Not sure about years, I think 69/70 probably. I used to share a lock up with a guy who had a '69 Lightning...thats how we knew the bits would fit.

Offline Housewiz

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Re: Preferred SR clutch set-up
« Reply #11 on: 17.11. 2012 01:23 »
Iain,

That's the/my story behind buying a parted out, non-running bike.  43 years ago I had a mostly stock '68 Firebird Scrambler and all I did was ride it hard and never worked on the thing.  It was the most reliable vehicle I ever owned.  The 2 college kids who bought it from me drove it to Brazil & back w/o breaking down - amazing.

I have to sort out this SR mostly through this fabulous Forum and several manuals I have purchased.  Already have bought a few parts I didn't need.  And more than likely paid too much for other parts.  Not a lot of Brit parts hanging around the middle of New York State. 

I will look into sourcing some upgraded clutch drive parts.

Thanks,

Steve