BSA Spitfire MkIV
|Manufacturer||BSA Motorcycles Ltd|
|Parent company||Birmingham Small Arms Company|
|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|
|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.
Spitfire Mark II
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.
Spitfire Mark III
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.
The fuel tank was enlarged to five UK gallons, which hampered both spark plug and carburetor accessibility. Both Mark II and Mark III UK models carried the traditional BSA 'flash' side-panel badges inset in the side cover gelcoat. The export Mark III, a majority of the Spitfires, had a transfer on the side covers similar (but not the same) as the other '67 model year machines.
Other modifications were Amal alloy (aluminium) control levers with click-stop cable adjusters, production of which BSA took over from Amal, marketed under their 'Motoplas' accessories branding, and the Zener diode voltage regulator was installed in an aluminium heat-sink mounted high on the front frame tubes to benefit from the cooling airstream.
Spitfire Mark IV
The 1968 Mark IV Spitfire was the last year of the 'Mark' Spitfires made. Amal's Concentric carburetors were combined with twin-leading-shoe front brakes and independently adjustable Lucas ignition points for easier starting and tuning. Engine power output was increased to 53 bhp (40 kW). A total of 1291 true 1968 model year Spitfires were produced, not counting the 478 'hybrid' 1968 Spitfires that have 1967 style numbers. The 'hybrids' were dispatched in March to May 1968 near the end of the 1968 model year.
- Motor Cycle, 21 April 1966. Road test Accessed 2013-06-28
- Motor Cycle, 16 September 1965. p.390. Brighton Show. Bright'n Breezy. Range-by-range Review and Prices Accessed 2013-08-09
- "BSA Spitfire". Retrieved 2009-07-15.
- Motor Cycle 3 August 1967 p.1 BSA Spitfire Mk111 full-page Advertisement Accessed 2013-08-09
- Motor Cycle, 21 April 1966. BSA factory advert. Accessed 2013-06-28
- Classic Bike review accessed 2008-05-05
- Motor Cycle, 10 November 1966, Earls Court Show Edition p.15 Amal factory advert for the 'new' Concentric and "wide range of controls, handlebars, etc. Amal Limited, Holdford Road, Witton, Birmingham 6." and p.632 Show Guide editorial, Stand 632 "New carburettors are rare...the neat 600 and 900 Concentric carbs are at Earls Court for the first time.". Accessed 2013-07-09
- Motorcycle Mechanics, March 1967. Road test Accessed 2013-06-29
- Motor Cycle 3 August 1967 p.1071 Amal – Motoplas levers "...manufacture of Amal solid light-alloy sports levers has been taken over by the BSA group. These will now be sold under the Motoplas name". Accessed 2013-08-09
- Motor Cycle, 1 December 1966. p.733. 'On the Four Winds' by 'Nitor'. "If you were looking at some of the BSAs at the Show, you were probably surprised at the size of the heat sink for the Lucas Zener diode located under the steering head. The Lucas boffins tell me that.....a diode may need to shed as much as 120 watts. Hence the vast departure from the sheet-aluminum sink cosily ensconsed under the dualseat." Accessed 2013-08-09