The Gold Star
The Gold Star
TDC
KEVIN CAMERON
BSA’S CLASSIC 350 AND 500CC GOLD Star Singles are the stuff of legend and were among the first production bikes that could also win races. Gold Stars won the Clubmans TT at the Isle of Man with such monotonous regularity that they were, like Yamaha’s TZ750s years later, vilified for being too good. Here in the U.S., Gold Stars won a huge number of dirt-track and other off-road events during the formative years of our sport in the 1950s and ’60s. In contrast with Britain’s pure racers like the Manx Norton or Velocette KTT, Gold Stars were practical road bikes with pushrod overhead valves—something any motorcyclist could afford and maintain.
Where did they come from?
When World War I ended, internalcombustion engine technology had made a great leap forward, mainly in the engines of the fast-developing aircraft that had fought above the terrible trenches. But what was the motorcycle to become? As the 1920s began in Britain, motorcycles put more people on wheels than cars did, and a golden age of motorcycling expanded.
BSA, maker of solid transportation vehicles, took a chance on racing. In 1920, a first try was given to four overhead valves in an aluminum head, but it overheated and went nowhere. In 1921, a big team was put together for the TT races at the Isle of Man, but inadequate testing resulted in a debacle: All the new ohv two-valve BSAs were out in three laps. No more racing on the Island! These engines addressed the new problem of how to lubricate overhead valve mechanism by not doing so; their rockers pivoted not on bearings but on knife-edge pivots. Other makers provided grease cups or oil cans for exposed rockers and pushrods.
The sport segment of the motorcycle market was going to want the extra performance that came with overhead valves. Head of the BSA drawing office, Fred Hulse, gave young Harold Briggs the task of designing BSA’s first ohv production model. Briggs knew that whatever he designed would have to continue BSA’s reputation for solid reliability. That meant no nonsense like grease cups or oil cans. Accounts say that for inspiration, Briggs looked at “an old Hotchkiss engine” that was somehow
in BSA’s inventory. That makes it seem like he was examining something out of the distant past, but this is where things get interesting. In fact, that engine had been designed in 1919 by air-cooling pioneer S.D. Heron for British Hotchkiss, who needed a product to make in its factory (the market for Hotchkiss’ previous product—machine guns—disappeared after the Armistice). A drawing of this Hotchkiss cylinder, signed by Heron, is in the Smithsonian in Washington, D.C.
Heron emigrated to the U.S. in 1920, the year after he designed that Hotchkiss ohv, 90-degree air-cooled V-Twin with advanced enclosed valve gear and plenty of cooling-fin area. Heron found work at the U.S. Army’s air-development lab, at McCook Field in Dayton, Ohio. There, he developed the type of air-cooled cylinder that made the large radial aircraft engine possible. Later, working for Wright, he supervised the assembly of the J-5 Whirlwind radial that powered Lindbergh’s 1927 trans-Atlantic flight.
Briggs gave BSA’s L-Model Single the same 45-degree included valve angle as on Heron’s design for Hotchkiss and would enclose pushrods and straight rockers in the same manner. Most importantly, Briggs also adopted the plentiful cylinder and head finning of the Heron design.
The L-model went on sale in 1924. Two years later, it was replaced by “the Sloper,” so-named for its forward-sloping cylinder. Its mushroom tappets looked very “Gold Star,” and it now had a detachable head with its valves at 90 degrees. Special Slopers with hotter cams and more compression were identified by a red star on the timing cover. BSA Singles evolved more and more modern features through 1936, when commemorating King George V’s Silver Jubilee, the latest model was designated “Empire Star.”
By then, it had then been 16 years since BSA’s TT fiasco. The company’s competitions manager, Bert Perrigo, decided to have another go. An Empire Star was modified to run on alcohol at a 13.0:1 compression ratio with special cams and a racing magneto. Racing great Wal Handley came back from retirement to ride this 34-horsepower bike in a three-lap handicap roadrace at the great Brooklands Speedway. Starting on a 9-second delay, Handley came through to win. For his achievement of a 100-plusmph lap, he was awarded a modest pin— a Brooklands Gold Star.
In that same year of 1937, new hire Valentine Page designed a full range of side-valve and ohv BSA Singles. Page, like Heron, traced his experience of engine design back to WW I aircraft work. All his new engines were given duplex oil pumps; a large scavenge section picked up oil from the crankcase sump and sent it back to cool in a remote oil tank. The smaller pressure pump drew oil from the tank and sent it to the crankshaft and top end. Well-lubricated parts last a long time.
When a special Empire Star sports model was made with its normal iron parts replaced by a 20-pounds-lighter aluminum head and cylinder, what could be more natural than to name it “Gold Star”? Only a few of these hot new sportbikes were built before the coming of WW II gave BSA the job of building 126,000 M20 side-valve sloggers for military use. Even so, a few early Gold Stars were with the British expeditionary force that was to be so dramatically rescued off the beaches at Dunkirk.
When the war ended, BSA began to produce first a 350 Gold Star and then a 500. In place of the prewar deep combustion chamber with its 90-degree included valve angle, these new engines had shallower, faster-burning chambers. Updates and redesigns took place steadily, and BSA Gold Stars distinguished themselves on both the highways and racetracks of the world.
Unfortunately, management saw big pushrod Singles as outdated, even though demand continued. The bigwigs nearly succeeded in excluding Gold Stars from the six special racers sent to Daytona in 1954. A BSA Twin won the 200 miler, and BSA Singles and Twins took five of the top six places.
By 1962, management had the excuse it had been looking fcr: Lucas was discontinuing single-cylinder magnetos. The sophisticated Gold Star, today recognized as among the great designs of all time, was ordered out of production. E3
