1940 BSA M20 with 1952 ZB34 Competition Engine

Winning Bid: $7,509.00

Item condition: Used

Auction finished

Reserve price has been met



1940 BSA M20 with 1952 ZB34 Competition Engine


The British motorcycle industry gained some real traction at the hands of the industry’s most prolific designers, Val Page. Page’s single cylinder range debuted for BSA in 1937, headed by the 596cc M21 and 496cc M20. Targeted to the sidecar market, the rugged M series came with rigid frames and girder forks and many M20s did sterling service as dispatch riders’ mounts with Allied forces during WW2.


In the late 1930s BSA became the world’s largest motorcycle factory, with advertising taglines like, “One in Four is a BSA”. The firm’s racing career was spotty at best in the early years until that time, when astride a new high-performance M-series single cylinder BSA, Wal Handley was awarded a Brooklands Gold Star for completing a 100mph lap of the famous banked circuit giving the award’s name to the Gold Star model. In 1946 BSA officially re-entered the competition field, with an annual run of B32 350cc and B34 500cc machines, which, from 1949 onwards, were fitted with plunger rear springing.

The motorcycle offered

The motorcycle on offer here is a perfect marriage of the rugged 1940 BSA M20 with a 1952 ZB34 competition engine at its heart. Built by a mechanic/restorer with designs on Frankenstein-type mad-professorship, the high compression engine was subject to a full rebuild including new piston rings, bearings, and Gold Star touring cams. At the top is an iron head with new valves and guides. The engine is mated to a 4-speed gearbox with new clutch assembly (plates, hub and bearings).

Other restoration points include:

  • New Old Stock Magneto Armature
  • Rebuilt Dynamo
  • New Old Stock wiring loom
  • Chronometric Speedometer
  • BSA Competition levers
  • New Saddle
  • New drive and primary chains
  • New steering head bearings
  • Brookland fishtail silencer
  • Rebuilt monobloc Amal carb
  • New brake linings, front and rear
  • New tubes

The bike is accompanied by a plethora of spare parts including a military gas tank.

The bike rides well and is a blast!

Race of Gentlemen, anyone???


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