[2] The engines had a reputation for vibration, but acceleration was good for the time, to a top speed of 100 miles per hour (160 km/h).

As part of a rationalisation by the newly formed Norton Villiers Triumph, production of BSA motorcycles ceased.

Precipitated by Lucas's intent to discontinue magnetos and dynamos in favour of alternators, BSA's managing director and general manager, Bob Fearon, took the opportunity to update the engines of BSA's twins and give them a new look.

The rear swinging arm was controlled by Girling 3 position adjustable shock absorbers.

This featured siamese exhaust, clubman handlebars, rearset footrests and a close-ratio gearbox.

[5] 1966 saw the rationalisation of the range and also the end to calling the same model different names in different countries: The high performance Spitfire model, designated Mk II, featured 10.5:1 compression ratio, a pair of Amal 1-5/32” GP2 carbs on open bell-mouths and a close-ratio gearbox.

The Spitfire evolved into the MK III model with the compression ratio reduced to 9:1 and the carbs changed to the new Amal Concentrics.

The US only Hornet offroader was discontinued and a new model, the "Firebird Scrambler", was introduced in all sales areas.

All models were fitted with twin leading shoe front brakes and carburettors changed to Amal Concentrics.

With the introduction of the flagship Rocket 3 750cc triple, BSA decided that there was no longer a need for the top of the range 650 twin and the Spitfire was discontinued.

To produce a 750cc machine for AMA Class C racing, BSA lengthened the stroke of Lightning's crankshaft by 11mm to give a displacement of 751cc.

[32] By 1972 BSA were in serious financial trouble and the Firebird Scrambler was discontinued in an attempt to reduce costs.

Designed by Edward Turner but substantially redesigned by Bert Hopwood and Doug Hele,[38][39] the Fury never went into commercial production due to the collapse of the BSA Group.

It was essentially the same motorcycle as the Triumph Bandit and represented the BSA factory's last attempt to compete against Japanese imports.

Featuring upswept twin silencers, the SS had an optional electric starter and indicators and 26 mm Amal concentric carburettors.