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Like other armament manufacturers of the period, Birmingham Small Arms (BSA) began manufacturing bicycles and bicycle components during the 1880s and after experimenting with motorised bicycles from 1905, produced the first 3.5hp BSA ‘motor bicycle’ in 1910.

After concentrating on single-cylinder engines during the early years, BSA produced its first V-twin in 1919, the 770cc Model E. It featured an in-line, 50-degree V configuration with side valves, an Amac carburettor, a seven-plate clutch, a three-speed gearbox, a kick starter, a choice of magneto or magdyno and a total-loss lubrication system with both a mechanical and a hand pump. It was produced until 1924 having been superseded by the 986cc, side-valve Model F in 1922. The 986cc model continued as the Model G until just after the beginning of World War II. These early V-twins were suitable for solo or sidecar use.

The Y13 was derived from an overhead-valve, 499cc, V-twin that was originally developed for military applications. However, the War Office rejected it in favour of side-valve singles and the V-twin appeared on the civilian market in 1934 as the J34-11. In 1935, it became the J34-12 and was joined by a 750cc model, the Y13. Production of the 499cc ceased at the end of 1936 but the Y13 was produced until 1938 with a total of around 1,600 examples manufactured. It is thought that only around one dozen of BSA’s last V-twin model survive.

With fittings for sidecar applications, the Y13 features a full cradle frame, a girder front fork, a steering damper and quick-adjust friction shock absorbers. The 750cc V-twin features aluminium alloy pistons, roller mainshaft bearings and a dry-sump lubrication system. It develops 26.5hp at 4,800rpm. The four-speed gearbox has a foot-operated gear lever and features two speed ranges suitable for solo and sidecar use, respectively. The sprung seat is adjustable and the handlebar is rubber-mounted to reduce vibration. The instrument panel with ammeter and oil pressure gauge is mounted in the tank and the headlamp can be unclipped for use as roadside illumination. It is equipped with metal toolboxes. With its stylish, sporting lines and high-quality build, it was considered by some as a competitor to even the Brough Superior.

This example was acquired in 2015 from a motorcycle dealer in Louisiana, USA.