plunger clutch anomaly

[RDfella]

Been messing with plunger clutch parts, mainly to identify modification possibilities (have one on my GFV2 but that's extensively modified with belt drive and ballrace at rear).
But here's the conundrum regarding parts I'm currently playing with: the rear collar that locates over the split ring (part no 67-3276/7/8) has a 1/4" deep boss on its clutch side - presumably the inner race for the rollers. But the clutch centre has the same boss meaning, if mounted together, the chain-wheel would have 1/4" lateral play and nothing to locate the rollers axially. What am I missing here?

[Greybeard]

From memory: The clutch basket has a race for the rollers that is pretty much flush with the back of the basket. The output shaft collar has a recess on the gearbox side for that two part ring. The front of the collar has a flat surface for the rollers that extends to the same diameter as the basket race outer diameter. So, the rollers are located longitudinally by flat surfaces on the collar and the clutch hub. The rollers are contained radially by the basket race

 I have an old clutch basket in my shed. I'll take photo's.

[Minto]

RD
The clutch side of that “collar” is flat, the only recessed part of it is to fit over the split ring on the shaft. I’ve had mine on and off so many times recently it’s indelibly etched in my mind.

[RDfella]

That's the problem - mine isn't. Which is wrong - the collar or the centre? I suspect the former.

[Greybeard]

I reckon this is correct:
http://www.cornucopia-enterprises.de/bsa_a7a10_catalogue/gross/dsc_3672.gif

[Minto]

Definitely the wrong thrust washer (collar), should only have the flange on one side where it fits over the split ring on the output shaft, clutch centre side should be flat. The clutch centre looks the same as mine from what I can tell from your pic.
If that was the assembly as was, surely all the rollers will have dropped out??

[Jules]

wow, those are the first real pics I've seen of the plunger clutch, what a masterpiece compared to the S/A version, now I understand all the comments about cost reductions!

[Greybeard]

wow, those are the first real pics I've seen of the plunger clutch, what a masterpiece compared to the S/A version, now I understand all the comments about cost reductions!

I did need to change the primary chain and clutch basket when I, (stupid basket!) allowed the oil to escape from the chaincase so the chain and sprockets got knackered. However, apart from that, I believe the components of the clutch on my bike are original. I've owned my 1955 bike for 50 years and I've never replaced the clutch plates. Yeh, I admit that I don't do many miles a year and I don't ride like I stole it, but the bike was hauling a sidecar before I bought it.

[Brian]

When you do find the correct collar be aware there are three different thicknesses of them to allow some alignment of the primary chain if necessary.

[orabanda]

I read that this very nice clutch was designed by Burman, for BSA; perhaps someone can confirm or provide more info?
They are a delight to use on my rigid and plunger A10's.
Richard

[Swarfcut]

 Looks like a homespun part to provide a new inner track for the rollers, enabling an otherwise good centre to  retained after cutting away  a damaged inner track boss. Needs must, back in the day?

 Swarfy.

[Greybeard]

From another thread, this picture clearly shows the same arrangement as the Plunger clutch hub.