BSA Golden Flash
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| Manufacturer | Birmingham Small Arms Company (BSA) |
|---|---|
| Also called | A10 |
| Production | 1950–61 |
| Predecessor | none |
| Successor | BSA A65 |
| Engine | 646 cc (39.4 cu in) air cooled twin |
| Power | 35 bhp (26 kW) @ 4500 rpm |
| Transmission | four-speed gearbox to chain drive |
| Wheelbase | 54.75 in (1,391 mm) |
| Dimensions |
L: 84 in (2,100 mm) |
| Weight | 375 lb (170 kg) (dry) |
| Fuel capacity | 3.5 imp gal (16 L) |
The BSA Golden Flash was a 646 cc (39.4 cu in) air-cooled parallel twin motorcycle designed by Bert Hopwood and produced by Birmingham Small Arms Company at Small Heath, Birmingham. Code-named the BSA A10, it was available in black and chrome; but it was the distinctive golden paint scheme that gave The Golden Flash its name.
Bert Hopwood served an apprenticeship under designer Val Page at Ariel. In 1936, Hopwood moved to Triumph, where he worked under Edward Turner to develop the 1937 Triumph Speed Twin. The innovative Speed Twin became the exemplar of the parallel twin engine layout for British motorcycles in the 1950s and 1960s. In April 1947 Hopwood joined Norton to design the Norton Dominator engine.
BSA, then the largest UK motorcycle manufacturer, was falling behind in the parallel-twin race. Although BSA had a parallel-twin, the BSA A7, they needed to develop the bike to remain competitive. In May 1948, the factory enticed Hopwood after only a year at Norton, and he was commissioned to create a competitive BSA parallel-twin. Launched in October 1949, Hopwood's A10 Golden Flash drew heavily from the A7 design by Page and Bert Perkins.
The A10 was increased to 650 cc (40 cu in), with a revised alloy rocker box and cast-iron cylinder head, plus an integral manifold for the single Amal carburettor. A semi-unit gearbox meant the primary chain was adjustable via a slipper tensioner within the primary chain case. The frame was available in rear rigid format, but the more common option was plunger suspension, adopted for the export market. The A10 featured a hinged rear mudguard to ease rear wheel removal. The A10 was so closely based on the A7 that it used many of its well-proven components, and this large carry-over of parts from the A7 promised greater reliability, with minimal risk of new technical problems.
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