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Author Topic: TRI 4 Spring Clutch Replacing BSA 6 Spring SOLVED THANKS!  (Read 2374 times)

Offline Peter Gee

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TRI 4 Spring Clutch Replacing BSA 6 Spring SOLVED THANKS!
« on: 27.12. 2017 12:03 »
Happy Xmas and a great New Year to all of you...

I have a 59 A7SS that was fitted with a 4 spring Triumph Pre-Unit clutch..or at least that is what came in the box. The original 6 springer ( or maybe BSA had already switched to 4 springers) is no where to be found. I hear this was a popular conversion and even the factory switched to it??

Is this just a straight swap or are there any distance pieces or shimming involved, or other parts from what are shown in a typical 1956 Triumph Pre Unit Clucth parts list??

I presume the Triumph clutch nut T1047 fits the BSA mainshaft? Clutch pushrod use BSA std or Triumph?

Any tips and hints appreciated.

Peter in Kenya
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Online JulianS

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Re: TRI 4 Spring Clutch Replacing BSA 6 Spring on A7SS Tips or Problems?
« Reply #1 on: 27.12. 2017 12:36 »
The factory changed to 4 spring in 1960.

It is a much better clutch and should fit straight on with no extra bits, presuming the parts are all there. Use a BSA nut and a BSA push rod, you might get away with the rod you have. Photo of parts book attached.

Sometimes the conversion was done with  a dynamo Triumph 500cc clutch which has one less of each plate and narrower hub.
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Offline Peter Gee

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Re: TRI 4 Spring Clutch Replacing BSA 6 Spring on A7SS Tips or Problems?
« Reply #2 on: 27.12. 2017 13:38 »
How can the Triumph Clutch tapered hub mate to the BSA mainshaft? The BSA mainshaft has a wide "lozenge" shaped keyway, whilst the Triumph clutch Hub 57-0418 has a narrow woodruff keyway or is a special hub required? Maybe this is a BSA part in your list kindly sent.

Thanks for your reply!
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Offline Dean

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Re: TRI 4 Spring Clutch Replacing BSA 6 Spring on A7SS Tips or Problems?
« Reply #3 on: 27.12. 2017 14:49 »
The cltch centre that fits on the taper is different for the BSA. Its sometimes called an adapter but was standard fit on 4 spring clutches fitted by BSA. In the event yours doesn't fit  the correct ones are readily available.

e.g. https://www.draganfly.co.uk/index.php/accessories-a-misc/product/8439-
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Offline Peter Gee

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Re: TRI 4 Spring Clutch Replacing BSA 6 Spring on A7SS Tips or Problems?
« Reply #4 on: 27.12. 2017 17:58 »
Many Thanks to all..the problem is solved! Happy New Year!!!!
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Online chaterlea25

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Re: TRI 4 Spring Clutch Replacing BSA 6 Spring SOLVED THANKS!
« Reply #5 on: 27.12. 2017 19:40 »
Hi Peter,
This change has been discussed many times here, 
It is worth a forum search to read the various encounters involved, start here
https://www.a7a10.net/forum/index.php?board=34.0

Getting the sprockets in line can cause problems,
Different shaft adaptor taper depths and engine sprocket /cush drive components cause anxt
https://www.a7a10.net/forum/index.php?topic=9646.msg70166#msg70166

John
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