Film notes
The project began with frame number KM20.5678. The machine was built with the large balloon tank, an eight-inch headlamp, field stand and valanced rear mudguard associated with the 1939 specification.
Although the KM20 originally used a 500cc side-valve engine, this motorcycle carries a later 500cc B33 overhead-valve engine. A 21-inch front wheel and lower handlebars further change its character. The owner describes the result as a much sharper and more powerful ride than the standard side-valve machine.
The finish combines early khaki green with aluminium and cadmium-plated details. The sporting direction was inspired by a period photograph of a captured KM24 Gold Star.
Follow the workshop
Subscribe to the Small Heath channel for new restoration films, close inspections and practical BSA workshop notes.

