After the 1938 launch of the Triumph Speed Twin, BSA needed a 500cc twin to compete in that class. Designed by Herbert Parker, David Munro and BSA’s chief designer, Val Page, the BSA A7 was the first of the BSA twin-cylinder motorcycles. Delayed by WWII, the model was finally launched in September 1946.
The very first A7 off the production line was flown to Paris for the first motorcycle show after the end of the war. There was huge demand for affordable transport after the war and the simplicity of the A7 twin was helped along by the slogan ‘It’s time YOU had a BSA!‘
The 495 cc (30.2 cu in) twin cylinder engine produced 26 bhp (19 kW) and was capable of 85 mph (137 km/h). The engine had a long stroke with a bore and stroke of 62 mm × 82 mm (2.4 in × 3.2 in). A single camshaft behind the cylinders operated the valves via long pushrods passing through a tunnel in the cast iron block. This system needed a considerable number of studs and nuts to fasten down the cast iron cylinder head and rocker-boxes, many of them deeply recessed and requiring well-made box spanners or the then uncommon sockets. As with other British motorcycles of the period, this kind of set-up regularly led to oil leaks.
Most motorcycles of this period tensioned the primary chain by drawing or rotating the gearbox backwards on a hinge with threaded rods, this was known as pre-unit construction. The first A7 had a fixed gearbox, bolted to the back of the crankcase, and an internal tensioner for the duplex primary chain. However, in 1954 when the swinging arm was introduced, the re-design reverted to the older system of a separate gearbox.
The Shooting Star was introduced in 1954 with a new swinging arm frame. The engine had a hotter cam, and compression was upgraded from 6.6:1 to 7:1. Power was up to 30 bhp (22 kW) at 5800 rpm, with a top speed of just under 90 mph (140 km/h). The earlier models had a dark green frame and a separate carburetor manifold fitted to the alloy cylinder head. By the end of production in 1962 the BSA Shooting Star was the culmination of the development of the BSA A7, with a black frame with light green tank, mudguards and side panels, it had an alloy cylinder head, a duplex cradle frame with swinging arm rear suspension, full-width cast iron hubs and 8-inch drum brake at the front with a 7-inch at the rear.
This particular 1959 example is of the later. Finished in polychromatic green with black frame, sporting the 30 bhp alloy-headed engine and separate gearbox.
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