Before the war the service colour in UK was gloss Brunswick Green. At the out brake of war the new service colour was mat khaki Green No3 (Gas Proof). Unfortunately there is no BS or equivalent RAL number. There are various formulas for mixing it. I've mixed it several times by trial and error to match the preserved paint I found inside the chain case and brake plates on this bike.  Ron

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John O'Brien is currently away from home and will check his records when he gets home tomorrow. He has crankcases with numbers very close to yours. Ron

I have some information on military KM20's and a friend has been collect information on Irish military bikes. If you can let me know the frame and engine numbers, I'll see what info is available.  Ron

The numbers on the front of the crankcase are just to confirm matching halves of the case. Is there something stamped on the left side below the barrel?  Ron

It looks very much like a 1929 B29 to me? Ron

Have you checked out Peter Long at Cornucopia. https://www.cornucopia-enterprises.de/spares-bsa_pre.html

Ron

Just to double up what Steve is saying. By the 40's for the M20, BSA had also decided that you can use two roller bearings on the drive side or alternatively one roller and one ball bearing...The ball bearing being the outer one. Ron

Here are the pages from the parts list. It should be proof enough. Whether or not the French authorities will except them is the question. I can email them if you message me your email. Ron

Yes Dave maybe it was a war time economy measure, saving a small amount of steel each time over 1000's of bikes. The war time RAF frames had the rear mounting on the nearside only. Post war frames had them both sides for foreign sales. Also for some reason? BSA used the Swallow chassis. But Norton used there own Chassis for the Swallow Model 8.

I'll scan the relevant pages from the parts list later in case they're of any use to Patrick.

Here in UK, all sidecars fitted after 1986 (or thereabouts) must be fitted to the left side.

Ron 

Well I'd suggest contacting the BSA Owners club directly or the VMCC and see if they can help with such a document.
https://www.bsaownersclub.co.uk/index

Ron.

Ah Yes Dave the AA And lots of other civilian variations, but Patrick specifically asked about the WM20. The WO contracts for the combinations were the only war time frames that BSA fitted with sidecar lugs Ron

Patrick I can't give you an "official" answer, but BSA prepared sidecar outfits for the RAF during WW2. I have an RAF parts list for these. They were fitted with a Swallow Model 8 sidecar and 18" wheels with 400-18 tyres.

These same Swallow sidecars were also fitted to Norton 16H, again mainly for the RAF.

Ron

OK can't help with that rare part. I eventually found one for my 1939 WD KC10. You can use the more common threaded type and make up a bush, Ron

Speak to roy van Dorp <roy206@hotmail.com> in NL. He makes this part. Ron

We're at cross purposes here Steve. You asked about the rollers. The only rollers I mentioned are in the M20 clutch.

Otherwise this is the type of 6 spring clutches I have.  Ron