Author Topic: TRI 4 Spring Clutch Replacing BSA 6 Spring SOLVED THANKS!  (Read 435 times)

Offline Peter Gee

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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

Offline JulianS

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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.

Offline Peter Gee

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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!

Offline Dean

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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-
Never tell people your troubles. Half of them are not interested and the other half are glad you're getting what's coming to you.

Offline Peter Gee

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Many Thanks to all..the problem is solved! Happy New Year!!!!

Online chaterlea25

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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
1961 Super Rocket
1963 RGS (ongoing)