Motorcycle specifications BSAThunderbolt 650 1962

There's no denying that Perfidious Albion's motorcycle production dominated its market for many, many years. And without doubt, if Japan hadn't gone to great lengths to steal the leadership in the late 60s, the many British brands would still be very much in evidence. Today, despite the efforts of many enthusiasts, some brands and models have faded into oblivion; or if they remain in the collective memory, it's only in a vague or anecdotal way. So, while the names Thunderbolt, Black Shadow, Thunderbird or Lightning evoke these old English cars, it's not always easy to associate a make, a displacement or an engine architecture with them.

The BSA A65-1T, also known as the Rocket 650 Thunderbolt, is one of those motorcycles with an evocative name.its presentation is a good excuse to rediscover this brand and its distinguished twin-cylinder machines.

This Thunderbolt appeared in 1962 as part of an already extensive range. The twin-cylinder is available in 2 displacements: 500cc and 650cc (30 and 40 cubic inches). The 500cc model was fitted to a road model, the Royal Star A50 and the WASP A50W scrambler. The 650 range comprises 4 models: 2 sport bikes, the Spitfire and Lightning, a Hornet Scrambler and the Thunderbolt road bike, which differs technically from the sporty Lightning in that it uses a single 28mm Amal concentric carburetor.

The engine is a 4-stroke twin-cylinder (2 valves per cylinder) with 360° timing, and a 4-speed gearbox. This engine, derived from the A7 (500cc) and A10 (650cc) of the early '50s, would evolve very little during its long career. Powerful for its time, the 650cc twin-carburetor version develops just under fifty horsepower. The Firebolt, with its single carburetor, is consequently a little less powerful, although it's difficult to find reliable data on this point.

Its reliability was, as legend has it, sometimes called into question, mainly because of the materialscrankshaft bearing bushes, for example, which were made of bronze and often wore out prematurely. But this fragility was relative, considering the general reliability of motorcycles at the time. It would take the arrival of Japanese production to really widen the technological gap and dent the image of British motorcycles.

Faced with the onslaught of the Japanese industry, offering powerful, reliable and economical models, BSA was forced to file for bankruptcy in 1971. Backed by Triumph, the brand continued to produce its twin-cylinder models for several more years, as well as the famous 750cc 3-cylinder Rocket III (twin brother of the Triumph Trident T150)

Now a rarity on French roads, the Thunderbolt remains a worthy representative of British motorcycling tradition, and still makes connoisseurs' eyes shine.

Tanthallas - Photos: Manufacturer

Thanks to the BSA Club of NSW Australia for permission to use their documentation.
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