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BSA Bantam History

The original design of the Bantam came from a German design, the DKW RT 125 (de) that was received as part of war reparations. This fact was not made widely known until long after the demise of BSA and for many years the Bantam was thought by many to be a 'truly British' lightweight motorcycle despite the original DKW design being taken up by two other manufacturers - Harley Davidson for one.

The BSA designers converted the design to meet British conventions - creating a mirror image - and into Imperial measurements for manufacture in Birmingham. This original Bantam, the D1, would continue to be produced for several years. Subsequent members of the Bantam range differed markedly in frame but their engine was a development of the original.

The first Bantams were available only in all-over "mist green", and sold for £60 plus tax. Later models changed distinctly from the original; over the years it gained improved suspension including a rear swinging arm, electrics and the engine size increased from 125 to 175 cc.

Engine

The engine is a unit construction (engine and gearbox of one piece) single cylinder 2 stroke. The barrel is cast iron while the head is alloy. The gearbox was initially three speeds, later versions went to four, fed through a "wet" clutch. Ignition was of two types a Lucas battery powered coil in earlier machines or a magneto by Wipac. The magneto was on a composite assembly sitting within the flywheel with its magnet inserts; windings gave power either directly to the lights (with a dry cell for when the engine was stopped) or through a rectifier into a lead acid battery. The early D1s had a flattened fish tail style exhaust. This was replaced with a more conventional round tube exhaust which ran at a higher level on trials and off-road models such as the "Bushman"

Models

Bantam D1 plunger frame suspension detail. The telescoping "cans" cover and protect the springs. The amount of inner can (chrome) showing and the position of the chainguard indicate the maximum travel that could be expected. The solid rod actuator for the rear brake can also be seen.
Main variants listed, most models were also available in competition form or with extra refinements. Nominal engine sizes given. BSA used a lettering system for their range of motorcycles. BSA decided to use a different letting system for the Bantam as it was a two-stroke, but with the introduction of the B175/D175 the company saw it more appropriate to label it with the "B" lettering system as by that time the engine size had increased to the capacity of those in the "B" category.