There are plenty of contenders for the title of “the bike that won the war” and the BSA M20 certainly has a fair claim to it. As the clouds of World War II ascended on the horizon, BSA were well prepared and in a position to drop some models, and up the production of others. The Army had a demand for motorcycles, and BSA stepped up with the M20.
The M20 was created by the new-to-BSA Chief Designer Val Page and was intended as a heavy-framed sidecar model with a simple 496cc air-cooled side-valve single producing 13hp at 4200rpm. The machine had low compression and plenty of low-end torque through a standard BSA box.
In 1936 BSA submitted a prototype M20 to the War Office; the bike was put through its paces but failed when the piston and cylinder needed to be replaced after approximately 6000 miles. BSA went back to the drawing board and resubmitted an updated model in 1937. The M20 passed the 10,000-mile suitability tests at the Military Vehicles and Engineering Establishment and a small batch were commissioned to test the water. The initial impressions of the M20 were mediocre as riders claimed that it was heavy, slow and had poor ground clearance. There were however some very positive traits that leant the machine well to warfare… it was resilient, reliable and easy to repair – ideal for the battlefield!
As the war continued to flare, so did the flow of orders for the M20. In 1939 the militarised M20 became the W-M20 and the production line became a hive of activity. The sheds at BSA were at full max and in addition to motorcycles, the factory was churning out vital components to the war that included Lee Enfield rifles, Browning and Besa machine guns, Hispano Suiza aircraft cannons and Oerlikon anti-aircraft guns. It was no wonder that the Small Heath factory was a key target of the Luftwaffe, and on the 19th of November 1940 the inevitable happened when a low flying aircraft dropped two bombs which destroyed the southern end of the BSA building in Armoury Road. The impact of the raid was shattering as 53 BSA workers aged from 18 to 68 were killed and a sizable portion of the factory and equipment was destroyed. It would not defeat BSA however, and production of the M20 was transferred to one of the other 67 factories in the vast complex.
The bulk of W-M20 motorcycles were used by the British Army but the Royal Navy and the Royal Air Force also commissioned the dependable machines from BSA which saw action in almost every theatre of war.
There were few updates to the M20 during the war period. In 1941 front and rear number plates were removed and between 1941 and 1942 active service use in North Africa showed the need for simple adjustment of the fork dampers. As a result, bespoke damper knobs were created from bakelite to enable this to happen. In 1942 there was a shortage of rubber in the supply chain and so the handlebar grips and foot pegs were replaced by canvas covered metal items; a new rear carrier was fitted the same year to hold universal WD steel pannier-frames and bags. In 1943 further modifications were made that included the addition of the Vokes high capacity air cleaner – a box shaped canister that sat on top of the fuel tank and was intended to assist operations in dusty environments.
The end of the war did not see the end of the M20. It had become apparent that the machine was hardy and resilient, and survived the harsh conditions of the war with few problems. This made the model an attractive proposition to the Armed Forces and so the M20 continued in military service throughout the national service of the 1950s and in smaller numbers until the end of the 1960s. In total an incredible 126,000 or so W-M20 motorcycles were made for the allies during WWII.
The M20 was a reliable and affordable form of post war transport, and so a number of W20s were repatriated and the khaki paint scheme painted black to make it more appealing to the general public.
The Automobile Association placed a sizable order and their yellow and black M20 combinations became a familiar sight on British roads. The M20 continued to roll out of Small Heath until 1955, and a 600cc cousin – the M21 – and the last side-valve to be built in Great Britain, soldiered on until 1963.
Was it the bike that won the war…? It certainly made a dent in it, so either way, the M20 is well worth a noble salute.
an article by The Girder Club
If you would like to be kept up-to-date with the latest news and information on vintage motorcycles, feel free to sign up to our newsletter, which we aim to ping out each month.
Leave a Reply