Triumph Bonneville T120

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Triumph Bonneville T120
Triumph Bonneville IMG 2734.jpg
ManufacturerTriumph Engineering
Also called"Bonnie"
Production1959–1975
Engine649 cc (39.6 cu in) air-cooled, ohv parallel-twin
Power46 bhp (34 kW) @ 6,700 rpm
Transmission4-speed gearbox (and later 5-speed) with chain final drive
Wheelbase55 inches (1,400 mm)
 
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Triumph Bonneville T120
Triumph Bonneville IMG 2734.jpg
ManufacturerTriumph Engineering
Also called"Bonnie"
Production1959–1975
Engine649 cc (39.6 cu in) air-cooled, ohv parallel-twin
Power46 bhp (34 kW) @ 6,700 rpm
Transmission4-speed gearbox (and later 5-speed) with chain final drive
Wheelbase55 inches (1,400 mm)

The Triumph Bonneville T120 is a British motorcycle that was designed by Triumph Engineering and built between 1959 and 1975, when it was discontinued in favour of the larger-engined T140.[1]

Development[edit]

1959 Triumph T120 Bonneville at The Art of The Motorcycle exhibition, Las Vegas

The Bonneville T120 was Edward Turner's last production design at Triumph[2] (in retirement Turner designed the Triumph Bandit/BSA Fury which did not pass the prototype stage before BSA went under[3]). The new motorcycle was conceived and developed so quickly that it was not included in the 1959 Triumph catalogue.[4] With a 649 cc (39.6 cu in) parallel-twin (two-cylinder) engine the T120 was based on the Triumph Tiger T110 and was fitted with the Tiger's optional twin 1 3/16 in Amal monobloc carburettors as standard, along with that model's high-performance inlet camshaft.[1] Launched in 1959 by Triumph as "The Best Motorcycle in the World", the Bonneville T120 was aimed mainly at the lucrative US market where enthusiasts were demanding extra performance.[5]

Initially produced with a pre-unit construction engine which enabled the bike to achieve 115 mph (185 km/h) without further modification, the power tended to induce high speed wobbles from the single downtube frame,[1] so in 1963 a stiffer and more compact unit construction model was introduced, with additional bracing at the steering head and swinging arm.[1] The steering angle was altered and improved forks were fitted a couple of years later, which, together with the increased stiffness enabled overall performance to match that of the Bonneville's rivals.[6]

1968 USA specification Triumph T120R Bonneville with unit 650cc engine

In 1967 Triumph posted its most successful year in the United States with an estimated 28,000 T120s sold,.[7] In 1968 the T120 gained a new and more reliable ignition system. From 1971, T120 models used a new frame which contained the engine oil instead of using a separate tank (this became known as the oil in frame/'OIF' version). A five-speed gearbox finally was fully available by 1972, but competition from larger-capacity motorcycles led to the T120 being superseded by the 750 cc Bonneville T140. Production of the 650 continued until 1973, when the workers at Triumph's Meriden headquarters staged a sit-in until 1975. In 1974 fewer than 1000 of the 650cc assembled machines were released by the workers, with another 38 in 1975. Production of the T120 was not resumed following the sit-in, the Meriden Motorcycle Co-Operative created after the dispute concentrating upon the 750cc twins instead.[8]

In the Harry Potter Films, one was used as Rubeus Hagrid's's Flying Motorbike.

T120 Export models[edit]

Close-up of 1968 T120R dual carburettor cylinder head, defining characteristic of the Bonneville line
1971 Triumph T120R Bonneville with the tall oil-bearing frame but still a 4 speed gearbox. Exhibited at the London Motorcycle Museum

Racing success[edit]

The T120 won the Production Isle of Man TT in 1967 and 1969. The re-introduction of the Production TT had just taken place in 1967 when John Hartle took first place on his Bonneville. Three years later Triumph set a new landmark in TT history when Malcolm Uphill averaged 100 mph (160 km/h) around the Mountain Course on a Bonneville. Uphill’s achievement was the first time that a production motorcycle had ever passed the three-figure mark from a standing start.[11] Following Uphill's record the Dunlop K81 tyres he was using were renamed 'TT100's.[12]

In 1962 Tony Godfrey and John Holder rode T120 Bonnevilles to victory in the Thruxton 500 mile endurance race, and an article in The Motor Cycle entitled "Thruxton Triumph by Bonneville" led to the development of the Triumph T120R 'Thruxton', which was hand-built by a team of Triumph technicians using specially picked components and precision-machined cylinder heads and crankcases. Peak power was increased and each 'Thruxton' engine was bench tested to deliver around 53 bhp (40 kW) at 6,800 rpm with a safe rev ceiling of 7,200 rpm. Only around 55 Thruxton T120Rs were built and surviving examples are rare.[13] In 1969, Bonneville T120 bikes achieved the first three places in the Thruxton 500.[1] Percy Tait and Malcolm Uphill finished first in the Thruxton 500, ahead of two other Triumph T120Rs.[13]

The Bonneville name[edit]

'Devil's Arrow' Triumph streamliner ridden by Johnny Allen to record speeds at Bonneville salt flats in 1955.

The Bonneville name came from the achievements of Texas racer Johnny Allen on the Bonneville Salt Flats in Utah. In September 1955, Allen had achieved a two-way average speed of 193.3 mph (311 km/h) on his special motorcycle the "Devil's Arrow", a 650 cc twin-cylinder Triumph engine fuelled by methanol in a unique 'streamliner' fairing. Allen's speed was ratified as a record by the American Motorcycle Association but not by the world authority, the FIM, as no official observers were present. German motorcycle firm NSU took the record the following year, so Allen and his team returned to Bonneville in September 1956 and won it back with an average speed of 214.17 mph (344 km/h). The FIM also refused to accept this as a world record but Triumph gained much needed publicity from the legal dispute that followed. After the Bonneville T120 had been named in recognition of Allen's records, other Triumph-engined motorcycles went faster still on the Salt Flats. In 1962 Bill Johnson set a two-way average of 230.269 mph (370.5 km/h) over a measured mile, riding a 667 cc 'streamliner' whose design was based on the American X-15 rocket plane. In 1966 Detroit Triumph dealer Bob Leppan raised the record to 245.66 mph (395.3 km/h) with his 'Gyronaut X-1', powered by two 650 cc Triumph engines. For the next few years, Triumph fitted Bonneville roadsters with "World's Fastest Motorcycle" stickers.[9]

Pair of USA specification 1969 Triumph T120R Bonnevilles at the London Motorcycle Museum, one sporting after-market direction indicators

See also[edit]

References[edit]

  1. ^ a b c d e Kemp, Andrew; De Cet (2004). Classic British Bikes. Mirco. Bookmart Ltd. ISBN 1-86147-136-X. 
  2. ^ "1965 Triumph T120 Bonneville". Retrieved 2009-02-21. 
  3. ^ Clew, Jeff (2007). Edward Turner: The Man Behind the Motorcycles. Veloce Publishing. p. 133. ISBN 978-1-84584-065-5. 
  4. ^ Brown, Roland (1999). The History of British Bikes. Parragon. ISBN 0-7525-3153-0. 
  5. ^ "The Triumph Bonneville". Retrieved 2009-02-21. 
  6. ^ The History of British Motoring, 2007. pp.166–167.
  7. ^ Neale Bayly (March–April 2011). "1967 Triumph T120 Bonneville". Motorcycle Classics. Retrieved 2011-03-07. 
  8. ^ The Rarest Bonneville Of Them All ? (Classic Bike 1/12)
  9. ^ a b "Triumph's Bonneville Connection". Retrieved 2009-02-22. 
  10. ^ "1971 Triumph 650cc Bonneville T120RV". Retrieved 2009-02-22. 
  11. ^ "Triumph's Return to Isle of Man". Retrieved 2009-02-22. 
  12. ^ McDiarmid, Mac. The Magic of the TT. Haynes Publishing. ISBN 978-1-84425-431-6. 
  13. ^ a b "Triumph Thruxton". Retrieved 2009-02-22. 

External links[edit]