The final and most exciting of BSA's long line of 'pre-unit' 646cc parallel twins, which had started with the Golden Flash back in 1949, came in 1962 with the launch of the mighty Rocket Gold Star. In the same year that the Birmingham firm introduced its new line of 'unit-construction' motors, with combined engine and gearbox, the Rocket Gold Star proved that there was still plenty of life in the old format.
The Rocket Goldie was inspired by a one-off special that Gold Star specialist Eddie Dow of Banbury in Oxfordshire had built for a customer several years earlier. That bike had simply been a Gold Star single with a twin-cylinder engine fitted. The production A10 RGS model incorporated a number of modifications to this basic concept, but was essentially a blend of BSA's Super Rocket engine in a chassis based on that of the Gold Star.

Twin-cradle frame

The frame was a twin-cradle design very similar to that of the single, but without the distinctive kink in its lower right loop that was needed to clear the Goldie's oil pump. The RGS look was very similar to that of the famed single, with chromed mudguards and a silver tank with chromed sides, plus the familiar Gold Star tank badge on a red circular background.
Cynics claimed the Rocket Gold Star had been created mainly to use up supplies of the pre-unit powerplant, which was uprated to power the new machine.

The specification included an aluminium cylinder head with higher 9:1 compression ratio, hotter cams, plus a race-style magneto with manual advance-retard adjustment. This combined to increase peak output slightly to 46bhp at 6250rpm, or 50bhp if the optional Gold Star-type racing silencer was used.
The twin's chassis was every bit as purposeful as the engine. The RGS was available with a variety of options, and was typically fitted not only with low 'Ace' handlebars, but also Gold Star gaitered forks, large-capacity aluminium fuel tank, close-ratio gearbox, siamesed exhaust system, humped racing seat, alloy wheel rims, big front drum brake in a full-width hub, plus matching speedometer and rev-counter.

That added up to a strikingly stylish bike that was every bit as fast as it looked, and which became highly regarded by the cafe-racer crowd in particular. Top speed was a genuine 115mph (185km/h) in good conditions, with 90mph (145km/h) cruising a practical proposition thanks to the tucked-down riding position. Handling was also good, though not perfect; one contemporary test reported that the front wheel tended to wander at very high speed.

In 1963, Motorcycle Mechanics magazine tested a production-race specification Rocket Gold Star which, tuned further with higher-compression pistons and special valve springs, recorded a top speed of no less than 123mph (198km/h). But at the end of that year BSA abandoned production of the model to concentrate on the new generation of unit-construction motors.

The Rocket Gold Star remains the most sought-after of the firm's pre-unit twins, and will long be remembered as a memorable way to end the line.