A ’39 M20

We do have interesting bikes come in for service by Gerry and his motorcycle maestros here at CSC.  How about this one…a 1939 BSA 496cc single-cylinder M20!

Manufactured from 1937 to 1955, the M20 was the mainstay of British military motorcycling during World War II, and it became the most widely used military motorcycle during the war.

Interestingly, the BSA firm originally started as a rifle manufacturer (BSA is the abbreviation for Birmingham Small Arms).   You can see the three crossed rifles emblem just above the crank on these iconic motorcycles…

The connection between motorcycling and armament is more common than you might imagine.   Royal Enfield is another motorcycle manufacturer that originally came to life as a rifle manufacturer.   And in an earlier life when I worked in the munitions business, bomb components here in the good old USA were manufactured by none other than Harley-Davidson.

These early British bikes featured both rebound and compression damping of sorts.  Damping adjustment was achieved by tightening or loosening the large knobs on either side of the girder forks (you can see the knob in the photo below).  This increased or decreased the friction on the hinged fork components.  Very clever, very simple, and it worked.  Harley had a similar setup on its earlier front suspension systems.

Like nearly all early British bikes, the M20 had Amal carburetion.  These carbs typically featured external float bowls with a “tickler” to get things underway.   My old Triumphs had the same deal.  You pushed down on the tickler two or three times, and that filled the float enough to prime the pump (so to speak), which made starting the bike a little easier.  The tickler is that little bronze-colored button sticking up from the float bowl in the photo below.

Here’s one last shot, this one showing the M20’s horn.   I didn’t have the keys (it’s a customer’s bike) or I would have tried the horn just to hear what it sounds like.  I’ll bet it sounds cool…

Britain’s M20 was a serious wartime motorcycle, so much so that Hitler’s Luftwaffe specifically targeted BSA plants during the war.   BSA lost 53 employees killed during bombing raids along with 89 folks who were wounded.

The M20 produced a whopping 13 horsepower, but it must have had gobs of torque as these motorcycles frequently pulled sidecars.   Like the one in the photo above, many of these are still being ridden today.