Restoration stories, technical knowledge and workshop notes devoted to the girder-forked BSA heavyweight singles built from 1937 and designed by Valentine Page — from the humble M20 sidevalve to the sporting OHV machines.
Discovered in Germany in 2010, the remains of this KM21 carried a brass Dutch-language plate on the toolbox. Its unusual professionally made components suggest that the motorcycle may have continued in German service after being captured in May 1940.
Read the restoration storyProjects, reference material, practical workshop notes and parts — organised around the machines rather than publication dates.
Discovered in Germany in 2010, the remains of this KM21 carried a brass Dutch-language plate on the toolbox. Its unusual professionally made components suggest that the motorcycle may have continued in German service after being captured in May 1940.
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A largely genuine Empire Star project found at the 2015 Netley Marsh Eurojumble, later reunited with the correct early-pattern frame and the original “Empire Star Green” revealed beneath later paint.
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A matching-numbers 1939 KM20, believed to have been left behind during the Dunkirk evacuation and later found in the Calais area.
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The WD M20 uses a strong single-spring, multi-plate dry clutch. This workshop tool makes compressing and fitting the spring considerably easier.
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A remarkably complete early WM20 found in Hermanville-sur-Mer, Normandy, with surviving military paint and a restoration decision still to be made.
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A 1939 KM20 built to early military specification, then given a later B33 overhead-valve engine and several sporting changes.
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A close inspection of the 1934 “Special from Florence”, recording its engine, frame, gearbox, controls and surviving competition details.
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BSA M21 engine in good condition, described in the original listing as ready to fit in a frame.
View the listingSmall Heath is an independent archive devoted to restoring, documenting and sharing knowledge about BSA’s girder-fork heavyweight M-series motorcycles. It brings together surviving machines, original details, restoration discoveries, workshop solutions and historical research.
About the archive
