Along with its 500cc cousin, the A50, the problems that beset the A65 typify much of what went wrong with BSA towards the end of the company. The machines had a poor reputation for reliability and spares back-up in particular which helped to put the final nails in the coffin of a large part of the British industry. And yet the design had its good points, for with modification the engine unit proved itself in that most demanding of competitions -sidecar racing - while surviving, hard-working bikes have clocked up thousands of trouble-free miles.

By the 1960s BSA had become part of a large conglomerate with diverse interests. There had been a concerted effort to introduce new systems, and there was an on-going drive to attract sales in the American market. Despite the popularity of the existing 650cc twins, they were perceived as being antiquated and were losing out against Triumph.

The new models were developed quickly, and many of their problems were the kind that a longer testing period would have ironed out. On the face of it, though, the new 650 offered promise, being more sophisticated and lighter than its AlO-based predecessors.

A unit-construction design with fashionable 'power egg' streamlined styling was coupled with a single, almost square, carburettor which promised a free-revving engine. It was perhaps surprising, therefore, that it initially offered less power than the top-of-the-range AlO-based machine, the Rocket Gold Star. The frame and forks.were similar to the duplex cradle unit of the late AlOs, and the handling was generally quite good, although the rather crude damping of the front forks found the going tough.

When the A65 and smaller A50 were launched in 1962, they appeared to have plenty going for them. The styling was in line with the clean, rather lumpy BSA look of the period. The performance was not bad, with strong acceleration and lOOmph top speed - and the fuel economy was good.
The problems soon appeared, however. The engines were prone to vibration, and the main bearings self-destructed at low mileages, often wrecking the engine. Oil leaks were common and the primary drive chain was also prone to wear.

This did not prevent an A50 from taking Gold in the 1962 ISDT, while for the public, the A65 was soon offered in higher performance versions with sportier styling, higher and higher compression ratios, and latterly, twin carburettors. One such machine, the 650 Lightning, even managed to win a production race in 1965. For the all-important American market initially, there were many more variants, including scramblers.

Power-egg' styling was a popular fashion in the 1960s, and the 650 BSA unit was perhaps the definitive version. All functions in the unit engine were smoothly faired in behind streamlined alloy casings.

By 1966 the top of the range was the Spitfire Mkll, which sported many racing fittings, such as close-ratio gears, a larger front brake and fibre-glass tank. It was light and fast, with 120 mph within reach, and thanks to a new front fork, handled well.

The introduction of I2v electrics was an improvement that benefited the whole range. But the vibration problems were still there and although attempts were made to find a cure, none succeeded. From 1970 on, this flawed power unit was coupled with a problematic frame. The oil-in-frame unit had a large diameter backbone which doubled as the oil tank. A similar design was adopted by Triumph, and although both handled well, the actual seat height precluded them being ridden comfortably by anyone much under six feet tall.

Handsome in a beefy way, the A65 offered true sports bike performance and the handling to exploit it
The model soldiered on until 1972, despite BSA's growing financial difficulties. By this time the seat height had been reduced to a much more workable level, handling was excellent and even the vibration seemed to have decreased. Sadly it was too late, and the A65 became a victim of BSA cuts.

A postscript to the story is that a solution to the main-bearing problem had been proposed while developing the factory racers in 1966-7, but never adopted. After the model had been discontinued, ex-BSA workers offered this as an after-market conversion, consisting of a new set of main bearings an optional new oil pump and clutch modification.