ABC Classic Bikes

In 1919, many motorcycle manufacturers who had been involved in war work found themselves facing the prospect of cutting back their activities unless they could diversify into other types of production. One such manufacturer was Sopwith of Kingston-on-Thames, Surrey, an aircraft company that faced a sudden downturn in demand. Proprietor Tommy Sopwith believed that motorcycle production could be the answer and turned to the designer Granville Bradshaw for help.

The solution that Bradshaw offered was the astonishingly bold ABC flat-twin - even more extraordinary because the design was completed in a mere 11 days! He had bet Sopwith that a prototype could be produced in three weeks - and backed up his bold claim with a deal whereby he stakes £100 per day over that time, while Sopwith would pay a similar sum for every day less. As a result, Bradshaw netted £1000 on the deal.

A bike built so quickly might have been expected to be crude, or at least a copy of an existing design, but the ABC was neither. Its horizintally-opposed twin-cylinder engine employed overhead-valves and it had an integral four-speed gearbox.

When it was launched, the ABC captured the imagination of the reviewers. Lightweight and quiet, the bike had a brisk performance, as well as being comfortable and stable. Orders began to flood in and the French company Gnome at Rhome were signed up to produce the design under licence.

Then the troubles began. Initially priced at £70, the ABC proved too expensive to manufacture and the design had to be modified to sort out some mechanical problems. Sales should have begun early in 1919 but when the first bike appeared in May 1919, the price had risen to an astronomical £160 and even at this price the manufacturers were hardly covering their costs.

Only some 2000 were made. Although the ABC's proved capable of winning two speed records in the year they were launched, it soon transpired that the valve gear was weak and prone to breakage. While accessory makers offered cures for its mechanical problems, the factory itself quietly let the unprofitable ABC fade away. The last one made by Sopwith was built in 1923, although Gnome et Rhome made a few up until 1925. After that it was left to others - especially the flat-twin BMWs - to demonstrate what the concept might have offered.

ABC (1919)

• Years in production - 1919-25
• Engine - horizontally opposed twin-cylinder overhead-valve four-stroke
• Bore and Stroke - 68.6 x 54mm
• Capacity - 398cc
• Carburettor - Claudel-Hobson
• Gearbox - four-speed with H-gate
• Top Speed - 70mph