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BSA Rocket Gold Star (A10)

Make Model	BSA Rocket Gold Star
Year	1962 - 63
Production	1584 units
Engine	Four stroke, parallel twin cylinder, OHV
Capacity	646 cc / 39.4 cub-in
Bore x Stroke	70 x 84 mm
Carburetor	Amal Monobloc
Cooling System	Air cooled
Compression Ratio	9.1:1
Lubrication	Dry sump
Exhaust	Single, stainless steel
Ignition	Lucas magdyno
Battery	6V
Starting	Kick start
Max Power	34 kW / 46 hp @ 6250 rpm Optional RRT 2 close ratio gearbox: 37 kW / 50 hp
Clutch	Multi-plate with built-in cush drive
Transmission	4 Speed
Final Drive	Chain
Frame	Welded seamless steel tubing with duplex front downtubes and full cradle engine support, bolted-on rear sub frame
Front Suspension	Telescopic forks with coil spring - hydraulically damped
Rear Suspension	Swinging arm, twin coil
Front Brakes	Drum, 8 in
Rear Brakes	Drum, 7 in
Wheels	Shouldered alloy wheels, wire spokes
Front Tyre	3.25 x 19
Rear Tyre	4.00 x 19
Dimensions	Length: 2100 mm / 84.0 in
Wheelbase	1391 mm / 54.75 in
Dry Weight	170 kg / 375 lbs
Fuel Capacity	16 L / 4.2 US gal
Top Speed	185 km/h / 115 mph

The BSA Rocket Gold Star (RGS) was a 646 cc (39.4 cu in) air-cooled parallel twin motorcycle produced by Birmingham Small Arms Company (BSA) at Small Heath, Birmingham. Launched in February 1962, it was one of the final range of A10 twins, using a tuned A10 Super Rocket engine in the double-downtube Gold Star frame.

Rocket Gold Star production ended in 1963 due to the development of new unit construction successors, designated as A65 in the 650 cc capacity.

Gold Star tuner and dealer, Eddie Dow, had a customer that wanted to be supplied with a Gold Star fitted with a Super Rocket engine. BSA supplied a Gold Star less engine and a separate Super Rocket engine. Dow assembled the special. The special was well received and the BSA management decided to put the concept into limited production. BSA had previously produced a bike with an A10 engine in a Gold Star frame - the 1957 Spitfire Scrambler. It has been suggested that as both the Gold Star and the A10 were at the end of their production life, and BSA wanted riders to switch to the new unit twins, this was a convenient way to use up the stock of pre-unit parts.

The later (1961-1963) 9:1 compression ratio Super Rocket engine was used with a 357 Spitfire camshaft and a 1 5/32" bore Amal Monobloc carburettor which gave 46 bhp (34 kW) as standard. Options such as an Amal GP2 carburettor, siamesed exhaust pipes and a close-ratio RRT2 gearbox could increase this to 50 bhp (37 kW) – and add 30% to the price. Nine specials were made for export to California and one was fitted with a sidecar by Watsonian for the Earls Court Show in October 1962.

The first pre-production bike was road tested by Motorcycle Sport magazine. The second was used as a TT marshal's bike, although a conrod broke during testing. It was repaired before the racing started. The bike was later loaned to Worcestershire County Constabulary to test.

The Gold Star frame used on the Rocket Gold Star has a frame number prefixed GA10. All other A10s have a frame number prefixed A7, including the 1957 Gold Star framed Spitfire Scrambler. The Gold Star singles required a kink in the bottom run of the frame to clear the oil pump. The kink is not present on the RGS frames.

The total Rocket Gold Star production was 1,584 bikes, of which 272 were off-road scramblers. Most were finished in red, but a few were manufactured in black or silver. The model was also known as the Gold Star Twin.

Source Wikipedia & Brian Pollitt

Photo from collectingcars.com

Article by Nolan Woodbury

Val Page provided the A7 twin's roots, but it was Bert Hopwood's A10 rework that gave the Rocket its legs. Released in 1947 the post-war A7 did little to change public perception of BSA, but 1954 signaled an upturn with the A10-based Road Rocket and a top-five sweep at Daytona didn't hurt either. Using the double-downtube frame design popularized on the DBD-series GS models, the RR featured swinging arm suspension, an aluminum head and a racing Amal carb. Able to cruise at 80-mph, that first Rocket allowed BSA to take a share of the market back. Uprated in 1958 to Super Rocket tune, by 1962 the A65 was ready to take over flagship duties, but not before BSA crafted the ultimate A10; lavishing the RGS with a full checklist of performance upgrades.

Retaining the 646cc bore and stroke and magneto-mandated 360-crank, the engine specs of the Rocket Gold Star illustrate the highest level of performance tuning BSA applied to the production A10 twin. These include some features carried over from previous Rockets (aluminum cylinder head and a racing magneto with manual adjustment) and adding high compression 9:1 pistons, the 357 (Spitfire) cam and an optional siamesed exhaust system with Gold Star pattern silencers. In this form, the RGS produced nearly 50-hp; good for an honest 115-mph. Another 10-mph was possible with the proddy racing pieces like pistons with even higher domes, special valve springs and the Gold Star racing exhaust.

Just as critical in the RGS's appeal is the period IOM style and stance borrowed from the Gold Star single. These include a distinctive humped racing seat, shouldered alloy wheels and a fork-mounted speedo/rev-counter/headlight mount. Available at extra cost (fitted, seemingly, sooner or later) were low 'Ace' bars, gaitered forks, an alloy fuel tank and a close-ratio gearbox. The result was motorcycle with few styling peers, and one that backed its looks with real speed and handling.

Probably the most desirable BSA short of the legendary Goldie, copies of A10-based Rocket Gold Stars are growing in number, so check your facts and figures before buying. Expect to pay a premium for original examples, and more for machines that include the desirable options

Photo from collectingcars.com