Two clutch sleeves

[Ron B]

Can anyone tell me the difference between the two six spring clutch sleeves, 65-3873 and 42-3107.  65-3873 is for the plunger bikes and 42-3107 is for the late A10 swing arm bikes.  Is there a difference or are they interchangeable?  Thanks Ron B.

[orabanda]

In my opinion, the plunger clutch is a good unit, and the swing arm unit is a challenge!

My rigid and plunger A10's both have the original clutches fitted, and they work well; light operation, no slipping, and smooth engagement.

I have fitted japanese clutches to my S/A bikes.

The plunger clutch is splined on the inner hub, whereas the S/A clutch innner hub is tapered.

I.e: the gearbox main shaft is different.

Richard

[duTch]

Hiya Ron,
            I agree with Orabanda, if you have a plunger clutch you're ahead. My experience with the S/A 6 spring('54-'58 I believe?) was such that they not worth a cracker!!! In fact I think I used a M20 clutch which worked fine, but that was a long time ago.
 However, and I haven't experienced the 4 spring('59 on?), but opinion suggests they're a better unit, and do have construction similarities to the plunger clutch, but a single roller chainwheel, and probably not worth doing unless options are limited.
     

       Just my opinion, cheers duTch

[orabanda]

Adding to Dutch's commentrs,
The 58+ clutch is a good clutch.
The infamous 6 spring clutch that preceded it CAN be made to work OK, but often not without lots of bad language!

Richard

[Goldy]

Coming back to your question Ron the sleeves are different. I built my clutch from a box of bits and there were three sleeves  all slightly different. I think the main difference is the position of the taper, which means the final position of the chain wheel, unfortunately I don't know which is which as I just found by trial and error.

[Beezageezauk]

Hi Ron,

I'm with Goldie on this one and had the same problem.  Yes, the clutch centre tapers are different and will allow the clutch to sit on the mainshaft at different positions.

If it goes on too far the rear of the primary chain can chip away at the adjuster slider mounting screws.  If it doesn't go on far enough the clutch can catch the primary outer cover when the clutch is operated.

After I got my '59 A10 running ok with a 6 spring clutch someone told me that when the clutch centre is positioned the mainshaft should be sticking through the end by 15mm.  However, I haven't checked mine since so please accept this figure with a pinch of salt.  Maybe somebody on the forum can confirm this dimension?

Beezageezauk.

[Ron B]

Thank you for the response on my clutch sleeve question.  The six spring taken from my B31/M21 doesn't fit on my A10 as it is too close to the sliding plate.  I see why now.  I tried something , took the four spring off the A10 and put on the B31/M21 combo.  Worked fine that way, but six spring to A10 did not work.  I will have to get the correct sleeve.  Thanks !!

[duTch]

Ron,
     Sounds like you have it sorted, but to not mislead anyone,I just did some research and the 'M20' clutch I used was apparently a WM20 , Aussie version if nowhere else, and also a '49-'58 WM21-AA (?). It's the one with the big mutha of an single internal spring- no adjustment but worked ok from memory, and  construction design of that is also 'similar' to plunger clutch but maybe not adaptable(?). I used it on my ~'58 rocket.
             Cheers,duTch

[BSA_54A10]

The single spring clutch was the pre-WWII clutch fitted to just about every thing except the V-Twins.
Post WW II BSA went to the 6 spring disaster or the 4 spring sweetie ( plungers ).
The two clutches can be swapped complete but each has a different center.
BSA only ever used one taper on its main shafts so in theory you could put just about any clutch on any bike if you are willing to play around with it.

[duTch]

You're probably right Trev, I just got that info from the Factory spares books on the DVD, and figure things are a bit variable, cheers

[KiwiGF]

By coincidence on my post on bottom gear interchangeability there's a pic of both types of mainshaft 6 spring a10 and plunger, no way a 6 spring center designed to fit on a taper will fit on the hex plunger mainshaft!

I've heard fitting the plunger mainshaft to a 6 spring box makes it easier to fit other clutches so I'll hang onto the plunger box I have until I see how the 6 spring clutch works out.

[BSA_54A10]

Probably better to talk about "bolt on" or semi unit boxes than plungers to avoid confusion.
The bolt on box fitted to plunger A series twins is a different animal to the box fitted to plunger B & M Series bikes.
The latter used the pre WWII box with 2 lower mounting points. It had a standard BSA main shaft with a keyed taper at the clutch end.

The A series Plunger box or bolt on used a totally different main shaft that was splined at the clutch end.
I have been told that it had either a Burman ( 4 spring ) clutch or a Burman designed clutch made by BSA under license.
Also the spline is the same as other bikes that used Burman boxes & clutches so clutches from other brands that used Burman gear can also be made to fit.
Being a totally one ( star) eyed BSA owner I have no way of verifying this as I have nothing to compare them with but in the back of the space where the brain is supposed to sit I have a recollection of an A 65 owner modifying a bolt on A series main shaft to fit in their hot A 65 for the specific purpose of running  a Notrun clutch.

[duTch]

Probably better to talk about "bolt on" or semi unit boxes than plungers to avoid confusion.

Good call Trev, I try and do that, but get sidetracked with the 'dark side' will exercise diligence.
  As has been discussed elsewhere recently, I got a Nortie diaphragm center/chainwheel fits straight on that shaft(but not in the case), and Musky has similar~ on his 'Cafe'-?

cheers,duTch

[muskrat]

 G'day all,
              I was led to believe that a sNorton clutch would fit on a semi unit shaft. I haven't tried as my '51 clutch works a treat. The one on the cafe sits on a s/a tapered shaft.
Cheers

[duTch]

Sorry Musky I stand corrected, about the cafe. but  the clutch centre fits the bolt-on box shaft spline, but from memory the chainwheel is too big to fit in the chaincase, forget by how much, maybe measure yours' diameter, keeping in mind I think the S/A single roller clutch is bigger dia. than the Bolt-on??

     cheers

Ps too bad about the footy hey!!