M 21

The BSA M21 is a classic motorcycle from 1937–1963, built around a 591 cc side-valve single. It is not a modern all-rounder but a characterful machine whose specification, output and finish can vary by year, export market and restoration history. The figures shown are therefore useful reference points, not a substitute for inspecting the individual bike. At viewing, compare engine and frame numbers, registration data, service invoices and visible modifications. On older motorcycles, rebuild quality matters more than the odometer alone.

For a buyer, the BSA M21 makes sense when its riding character, parts availability and maintenance demands fit the intended use. Take a calm test ride and assess clutch, gearbox, brakes, suspension and charging system once warm. Check that the machine is complete: original components, a correct exhaust and tidy wiring make ownership much easier. A specialist pre-purchase inspection is sensible where provenance or engine work is unclear. Choose a cared-for, documented example over an apparently cheap restoration project.