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1949 650cc 6T Triumph Thunderbird

1949 650cc 6T Triumph Thunderbird

In the autumn of 1949, Triumph launched its first post war 650cc twin with a dazzling display of performance and reliability. Three machines, ridden to France from the company's Meriden factory, maintained 90mph for a distance of 500 miles on the banked Montlhery circuit near Paris. They then completed several flying laps at a steady 100mph before being ridden home - all on the poor 72 octane petrol of the time.

The 6T Thunderbird was named by Triumph boss Edward Turner, who got the idea on a business trip to the USA. In native American lore, the mythical eagle-like Thunderbird could unleash thunder, lightening and rain. With its hot new perfomer, Triumph aimed to create a storm on the lucrative transatlantic market.

On similar lines to the successful 500cc 5T Speed Twin introduced in 1938, the Thunderbird's engine had larger bores, raising capacity to 650cc. It gained an extra seven horsepower, but with the same cycle parts, the power-to-weight ratio was much improved. Acceleration was lively and the bigger engine cruised in a more relaxed way, at lower revs. Like other Triumph twins of the period, the Thunderbird was equipped with sprung hub rear suspension and a streamlined nacelle for the headlamp, containing a speedometer calibrated to show rpm in the four gear ratios.

A Triumph Thunderbird famously featured in the controversial 1953 film The Wild One, starring Marlon Brando.


  • Engine - 649cc (71 x 82mm) air-cooled overhead valve paraller twin, 7:1 compression ratio, 1 1/16in Amal carburettor, magneto ignition.
  • Transmission - Chain primary drive, wet multi-plate clutch, four speed gearbox, chain final drive.
  • Chassis - Cradle frame, telescopic fork front suspension, sprung hub rear suspension, drum brakes.
  • Wheels - 19in.
  • Power - 34bhp @ 6300rpm.
  • Dry weight - 385lb (175kg)
  • Top Speed - 100mph.