• Year of manufacture 
  • Motorcycle type 
  • Engine number 
    523 (2435)
  • Lot number 
  • Condition 
  • Colour  
  • Location


1921 BSA 4¼hp Model H
Registration no. NX 6423
Frame no. K240
Engine no. 523 (2435)

• Desirable 'all chain' model
• Un-restored condition
• Ideal 'Banbury' bike

Originally established in 1861 as an armaments manufacturer, The Birmingham Small Arms Company switched to making components for the bicycle industry in 1878 following a Government-induced downturn in the arms market. BSA first experimented with powered two-wheelers in 1905 using a standard-type bicycle. This first motorcycle made by BSA used a proprietary engine - probably the Belgian Minerva - clipped to the front down-tube, but it was not until 1910 that the firm introduced a model entirely of its own design and manufacture. Displayed at that year's Olympia Show, the first series-production motorcycle to feature the marque's distinctive green and cream tank colours was a 499cc (3½hp) sidevalve single, built initially with single-speed, belt-drive transmission and later on with a three-speed countershaft gearbox. Well engineered and equally well made, this first BSA proved an enormous success and changed little over the next few years, though for 1912 a two-speed hub gear was available together with an all chain drive model suitable for sidecar work. For 1914 the range was augmented with a 557cc (4¼hp) long-stroke version featuring a strengthened frame and the new three-speed gearbox, which was designated Model K if fitted with chain-cum-belt transmission or Model H with fully enclosed all-chain drive.

BSAs of the early 1920s were essentially developments of pre-war models. The Motor Cycle's celebrated correspondent, Ixion, tested a 4¼hp model in 1920 and wrote: 'I did not know that a single-cylinder could develop so much power. I never unearthed a gradient that could bring her down to first, using that gear only for starting off. And talk about substantial! The BSA is built like a tank and is fundamentally incapable of fracturing anything, whilst she creates the pleasant impression that nothing will ever wear out.'

This delightful un-restored Model H appears substantially complete, retaining the all important primary and final drive chain enclosures. It also carries a tax disc that expired July 1967. The BSA was acquired for the collection in 1993. Accompanying documentation consists of an old-style continuation logbook, 1997 tax disc, old V5 and V5C registration documents.

Bonhams 1793
101 New Bond Street
United Kingdom
Contact Person Kontaktperson
First name 
Bonhams Collectors’ Car department