BSA Spitfire
BSA Spitfire MkIV
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| Manufacturer | BSA Motorcycles Ltd |
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| Parent company | Birmingham Small Arms Company |
| Predecessor | A65L Lightning |
| Engine | 654 cc (39.9 cu in) air cooled four stroke, parallel twin, OHV, 2 valves per cylinder, 2 Amal 10GP2 carburettors, five pints of oil |
| Power | 54 bhp (40 kW) (claimed) @ 6900 rpm |
| Transmission | 4 Speed, chain |
| Suspension | BSA telescopic front fork with two-way damping, Girling rear shock absorbers with three-position spring adjustment |
| Brakes | 190mm (7.5 inches) front, 180mm (7 inches) rear |
| Wheelbase | 56 inches |
| Fuel capacity | 4 gallons (2 in the US export version) |
The BSA Spitfire was a high-performance BSA motorcycle made from 1966 to 1968 with model designations of MkII, MkIII and MkIV. Announced at the Brighton motorcycle show held during September 1965, it was based on the earlier BSA Lightning with a power-upgrade achieved by higher compression-ratio 10.5:1 pistons and two large-bore Amal GP carburetors with velocity stacks it was one of the first BSAs to have 12-volt electrics. At introduction in 1966, it was the fastest standard BSA ever produced and the fastest standard motorcycle tested by Motor Cycle with a best run at 123 mph and average of 119.2 mph The Spitfire was used for travelling Marshalls' course duties at the 1967 Isle of Man TT races.
The first A65S Spitfire of 1966 was confusingly designated Mark II and had a number of new features including two-way damped front forks, Girling shocks and a brace between the downswept exhaust pipes. A 190mm front drum brake improved braking and lightweight alloy rims reduced the weight to 174 kg.
The bike was supplied as a sports-tourer with raised handlebar, forward-mounted rider footrests, a large dual seat with race-styled hump, and the glass-fibre fuel tank and side panels covering the oil tank/tool compartment and battery were finished in Peony Red. The UK Spitfire had a conventional four gallon tank, with a large five gallon option from 1967.
A selection of factory extras were available to enable the model to enter Production Races, including a fairing and single racing seat.
Two large-bore Amal GP carburetors with velocity stacks improved acceleration but made the Spitfire hard to kick start when the engine was hot, so owners chose to replace them with Amal concentric carburetors with more conventional round air filters and this became the factory supplied specification in 1967. Keen to boost sales in the US market BSA produced a Spitfire with a two gallon fuel tank following the trend set by the Harley Davidson Sportster.
For the 1967 Model Year (MY) the Spitfire was upgraded and designated as Mark III. The racing Amal GP carburettors with open-intakes (bellmouths) were replaced by Amal Concentrics with individual chome filters which enabled better low-range engine response.
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