There were no JM prefix 20 or 21 supplied to the War Office so it would perhaps be worhtwhile to ask the BSA OC or the VMCC where that engine went to.
The Inspection mark (is it 39 or 89 ?) will apply to the individual inspector rather than be a year indicator. Unlike many factories,where all the early-war engines were inspected, BSA seem to have only been subject to occasional controls. Does anyone else have a similar stamping ? These inspectors only seem to have stayed 6 months or so at each location. I can date early-war Nortons in this manner.
If the breather is on the timing side, it sounds like post war crankcases to me. Email me the pictures if you want and I'll add them in this thread. Ron
Pics emailed to Ron Pier.
It’s an interesting bike I think.
Inspector M89 stayed at the BSA factory in the (late) 1939 - (early) 1940 period. I have these examples in my Register:
KM20.1376, KC10.1779, WC10.552, WC10.583, WC10.720, WM20.11612.
The next one in my list is WM20.20576, with acceptance marking M^65.
So far as the bike is concerned I plan to keep it mostly as is ‘ex government’ trim. It appears to have been black since it’s wartime use except for the green tank panels which look to have been added later. I am quite happy with its current engine for now as it’s original engine JM23 159 is unlikely to be found or any JM23 engine for that matter. I may think about fitting a later B/M ohv engine one day.
Inspector M89 stayed at the BSA factory in the (late) 1939 - (early) 1940 period. I have these examples in my Register:
KM20.1376, KC10.1779, WC10.552, WC10.583, WC10.720, WM20.11612.
The next one in my list is WM20.20576, with acceptance marking M^65.
