BSA Rocket Gold Star
When Triumph released the Speed Twin in 1937, it threw the gauntlet to the rest of the British motorcycle industry, forcing them to follow suit. As the twin looked similar to the ubiquitous single, was lighter, and only slightly more expensive, it was anBSA, Triumph's main competitor, wasted no time in developing its twin, and had a development machine running by 1939. World War II intervened and the first production BSA twin, the 500cc A7, appeared in 1947. By 1949 it grew to the 650cc A10, and the twins ran through until 1962 when they were replaced by the A50 and A65.
Like many British designs, the A7/A10 had its roots in an even earlier design, in this case Val Page's Triumph Model 6/1 of 1933. The 360-degree twin, with a single camshaft at the rear of the crankcase operating all four pushrods, and a four-speed gearbox bolted in semi-unit form to the rear, set the form that would remain basically unchanged throughout its life. However, the twins were never really considered high-performance motorcycles until the release of the A10 Super Flash of 1953. Then followed a series of hotter 650s, culminating in the spectacular Rocket Gold Star of 1962.
The impetus for the Rocket Gold Star came from Gold Star specialist Eddie Dow, who was also involved in developing performance parts for the twins. The Gold Star single was the epitome of the factory café racer, the machine that you could ride to work during the week and race at weekends, but it really had its day by the end of the 1950s. Unable to obtain a life extension for the Goldie, Dow persuaded BSA management to slot a Super Rocket engine in Gold Star running gear to produce a hybrid flagship. It also provided a bonus of using up old stock in the wake of the new A65 twin, but the resulting Rocket Gold Star ended up overwhelming its replacement.
With the long-stroke 70mm x 84mm engine fitted with an alloy cylinder head, sporting cam, and higher compression pistons, it produced 46PS at 6250rpm. Each engine was bench tested, and only the best made their way into the Rocket Gold Star. Initially, the gearbox was also the very close-ratio RRT2 type of the Goldie single, and there was a wide range of performance options.
A megaphone exhaust pipe for the special siamesed exhaust system allowed 50PS, and other options extended to light alloy rims and larger brakes. The duplex frame came straight from the Goldie, but without a distinctive kink in the right hand side to allow for the single's oil pump. Also from the Goldie were the gaitered forks and quickly-detachable headlamp. The Rocket Gold Star was definitely one of the finest factory cafe racers, but it was more suitable for street use as it wasn't particularly successful on the track, at least as a solo.
As the ultimate development of the A10, the Rocket Gold Star was more of stylish roadster, providing excellent performance, with a top speed of around 170km/h, fine handling, and exceptional good looks. With the A65 unit construction successor nearing production at the same time as the Rocket Gold Star, it only lasted for two years. Now this last A10 is considered one the finest British twins, not only eclipsing its successor but most other motorcycles of the era.
FIVE THINGS YOU DIDN'T KNOW ABOUT THE BSA A10 TWIN:
- 1. Although BSA concentrated on developing the single-cylinder Gold Star for solo racing during the 1950s, the twin was successfully adapted for sidecar racing.
- 2. One of the first sidecar successes for the BSA twin was in the 1952 Milano-Taranto road race when Leopoldo Tartarini and Sergio Calza won the sidecar class at an average speed of more than 80km/h.
- 3. Chris Vincent successfully raced an A10-powered sidecar from 1959, winning the 1962 Sidecar TT at the Isle of Man, then a world championship event. This was BSA's maiden TT victory.
- 4. Ariel, bought by BSA in 1944, also produced the Huntmaster from 1953 until 1959 with a thinly-disguised A10 engine in an Ariel frame.
- 5. The A10 lived on long after its demise in England in the form of the Kawasaki W-series, originally the Meguro K1. Kawasaki offered the W3 through until 1975 - not bad for a design that first emanated in 1933.
By Ian Falloon, Australian Motorcycle Trader
Please see our Editorial Guidelines & Code of Ethics (including for more information about sponsored content and paid events). The information published on this website is of a general nature only and doesn’t consider your particular circumstances or needs.
