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BSA Motorcycles

BSA OHC Twin 1938 Prototype

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The BSA overhead cam vertical twin is an intriguing prototype from 1938, and was reputedly capable of 100mph, just like their Gold Star. The design is very clean, especially on the cylinder head.

It is generally held that the prototype was lost during wartime bombing and that marked the end of OHC twin experiments until the 1960's.

In unpublished memoirs of his time as a development engineer with BSA, Roland Pike says that in 1952 BSA were working on another single overhead camshaft 500 twin.

It had an alloy head and barrel, fine pitch finning, and exhaust pipe held to the head by nuts. The single overhead cam was driven by bevel gears and a shaft running up what would normally be the push rod tunnel. The valves were operated by rockers.

It suffered from lubrication problems and a weak crankshaft that could have been resolved but BSA ran out of enthusiasm the project went no further.

Text courtesy Athanasios Karalias, image courtesy Neil Harris. From a post by Sergio Scalerandi