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.

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

Getting the sprockets in line can cause problems,
Different shaft adaptor taper depths and engine sprocket /cush drive components cause anxt

1961 Super Rocket
1963 RGS (ongoing)