c1969 BSA A65 Thunderbolt 650cc Motorcycle
One of the oldest British motorcycle manufacturers, the Birmingham Small Arms Company began building bikes with proprietary power as early as 1903 and by 1909 were using their own engines, starting with a 3.5 horsepower belt-driven single. BSA went on to become one of the most successful of all British manufacturers, both on and off the track, building a diverse range of bikes through the 1920s and 1930s that kept the company alive during the Depression. A development of the successful A10, BSA's new range of A50 and A65 twins took advantage of unit construction to modernise the packaging of the engine and gearbox in the late 1950s and would remain in production from 1962 until BSA finally went under over a decade later. The two models shared virtually all common parts, including their stroke of 74mm, with the 500cc A50 having a bore of 65.5mm and the larger 650cc A65's bore 75mm. With a new frame came a new name, the so-called "Power Egg", a reference to the design of the new unit engine and gearbox. The A65 was sold in a myriad of different versions, including the Rocket, Thunderbolt, Lightning, Spitfire, Hornet and Firebird, and was steadily improved over the years. The Thunderbolt, as offered here, was designed for touring, with a single carburettor, 12-volt electrics, twin coil ignition, two-way fork damping and the single-sided front brake lifted from the Gold Star. The Thunderbolt also had a three-spring clutch and proved popular in the crucial US market. In 1968 several changes were made to the specification, including a longer kick start and metal tank badges replaced the earlier plastic ones. Perhaps more important, an Amal concentric float carburettor reduced problems of fuel flooding. With 46 horsepower, the A65 Thunderbolt had a very respectable top speed of 107 mph, with a cruising speed of 70 mph. By the late 1960s, BSA (along with the entire British motorcycle industry) was struggling in the face of the onslaught of competition from Japan and production at the Small Heath factory in Birmingham ended in 1972. The A65 Thunderbolt matured into a fantastic machine by the time the machine offered here was made and expert Roy Bacon commented "for riding, a well-sorted Thunderbolt from the late 1960s could give the best combination of virtues."