Modifications
From October 1939 the K-M20 was designated the W-M20 and modified to include girder-forks and removal of the valanced rear mudguard. During late 1940 some civil specification M20s were purchased by the War Office which were civil models with a military paint scheme. In 1941 front and rear number plates were removed and between 1941 and 1942 active service use in North Africa showed the need for easy adjustment of the fork dampers. Special damper knobs were made of bakelite (later replaced with pressed steel). The DU142 headlight was replaced with a smaller 6 in Lucas DU42, with a hooded, slotted black-out shield, and a universal L-WD-MCT1A tail light was fitted.
From 1942 there was a shortage of rubber so handlebar grips and foot pegs were replaced by canvas covered metal items and production was standardised, with only minor modifications until the end of World War II. By early 1942 a new large rear carrier was fitted to hold universal WD steel pannier-frames and bags. This meant repositioning the long prop stand to forward of the nearside rear wheel spindle nut. In 1943 further modifications were made include redesign of the crankcase sump shield and fitting of the Vokes high capacity air cleaner, which was a box shaped canister on top of the fuel tank and was intended to assist operations in dusty environments. In early 1945 a push-button switch was introduced for the headlight and the main lighting switch relocated to a bracket beneath the offside of the saddle.
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