Back in the early 1960s, many British bike companies were cheerfully warring with each other, paying no attention to the threat coming from the Orient. The major market for their 650 twins was the U.S., and Americans wanted horses—lots of horses. The more the better. Well-mannered commuter twins did not sell worth a damn to the power-crazed Yanks, who looked at quarter-mile times and top speeds as the main virtues of any motorcycle. Dependability? Who cared? The commute to work was done in a Ford or a Chevy.
Harry Sturgeon, BSA’s managing director, decided to give the ex-colonials exactly what they wanted, a hot-rodded, highly chromed, Royal Red 650 twin called the Spitfire that could blow off any hapless rider on a Triumph Bonneville or Royal Enfield Interceptor. The first rendition, in ’66, was labeled the Mark II, as BSA had previously used the name in the Spitfire Scrambler of 1957.
Claiming 55 horsepower and a top speed of 120 mph, the Mark II was the kind of kick-ass motorcycle that manly men chose to ride. As Cycle magazine’s road test warned, it was “… a full-fledged racing motorcycle disguised as a snarling street bike.” Another article described it as “tuned to the boiling point.” Moto-journalists have long been prone to mild exaggeration.
A little history is in order. What was happening was that the Brits did not have much in the way of R&D money to build new motorcycles, so they continued to pump more ponies out of 30-year-old technology. The blame for this can be laid on Edward Turner, who came up with the vertical twin design on the Triumph 5T Speed Twin in 1936. Apparently one could not patent such a thing as this engine configuration, so BSA immediately began developing its own version, which was delayed by the advent of World War II. But late in 1946, BSA’s A7 500 was presented to the public.
Turner upped the ante in 1949 by creating the 650cc Thunderbird, and came out with the famous dictum that 650cc and 6,500 rpm was as far as a vertical twin should go. This was long before any counterbalancing technology was in effect. BSA followed a year later with its own 650, the A10 Golden Flash, using a bore of 70mm, stroke of 84mm, equaling 646cc. Incidentally, in 1951 BSA bought the Triumph company, though the two brands were kept well apart.
Carbs, cams and compression ratios were the popular ways to make these bikes go faster. In the 1950s, dual carbs were popular as an option on these twins, but no stock bike had them until Triumph brought forth its Bonneville model in 1959. Bumpier camshafts were easily available, and compression was merely a matter of shaving heads.
BSA’s minor effort at modernity came with the unit-construction A65 Star for 1962. It maintained the 360-degree crankshaft, a single camshaft, and single Amal Monobloc carburetor of the non-unit A10, though it had an enlarged bore of 75mm and shortened stroke of 74mm for a total of 654cc. As well as 12-volt electrics, with an alternator and two coils.
Another change was a shortened chassis, 56 inches between the axles, though still the double-cradle design of old. The fork was two-way damped, and Girling provided the shock absorbers with spring preload adjustability. Weight was close to 400 pounds.
That first A65 was a pretty benign bike, having a modest compression ratio of 7.5:1 with an output rated at some 38 horses at 5,800 rpm. After a year or so, BSA realized that it was going to have to give the Yanks more power, and came out with hotter versions, the Rocket and the Lightning. Then Sturgeon said something to the effect of “Screw it! Pull out all the stops.” And the engineers did, pumping up the compression ratio to a heart-stopping 10.5:1, bolting on a pair of Amal GP carburetors, and claiming 55 ponies at 6,800 rpm. Sales for the Spitfire were helped by those ads claiming it to be a 120 mph machine—which it was, with a gentle tailwind helping.
Unfortunately, holding the throttle open at over 6,000 rpm meant the bike vibrated like a paint shaker. Also, if the engine was run at those speeds for any sizable amount of time, the crankshaft bearings might fail, as there was a bronze thrust pad on the timing side to deal with end float that was prone to wearing excessively and inhibiting lubrication.
Starting the bike, which had a central float bowl between the GP carbs with a hard-to-get-at tickler, could initiate some strong language from the rider. Especially with the 10.5 compression. As one critic wrote, it was barely civilized. But once the rider was barreling down the road at full tweet, all of that went away. The Spitfire demanded, and got, respect.
For the ’67 Mark III version, the GP carbs were tossed, replaced by a pair of new Amal Concentric 932s, and the compression ratio was lowered to 9:1. For ’68, the Mark IV sported a new twin-leading shoe front brake.
Then the Rocket III triple appeared in September of 1968, and BSA decided to drop the Spitfire and let the new machine take the role of fastest bike in the lineup, with the more modestly tuned Lightning filling the role of top twin. The spitter of fire was not much missed.
(This Retrospective article was published in the October 2014 issue of Rider magazine.)