The original Triumph Bonneville was popular (particularly in its early years) for its performance compared to other available bikes. Although its motor was later enlarged to 750 cc, in the late 1970s and early 1980s sales abroad greatly suffered in competition with more modern Japanese motorbikes from Honda and other manufacturers. Domestically, however, the T140 remained the best-selling 750cc motorcycle against more sophisticated Japanese and Italian opposition , picking up the prestigious Motor Cycle News Machine Of The Year award in 1979.
The original Triumph Bonneville was a 650 cc parallel-twin (two-cylinder) motorcycle manufactured by Triumph Engineering Co Ltd and later by Norton Villiers Triumph between 1959 and 1974. It was based on the company's Tiger 110 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. Initially it was produced with a pre-unit construction engine which enabled the bike to comfortably achieve 115 mph without further modification, but later (in 1963) a unit construction model was introduced which was stiffer and more compact, including additional bracing at the steering head and swing arm. 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. Later T120 Bonnevilles used a new frame which contained the engine oil instead of using a separate tank; this became known as the oil in frame version. The T120 engine, both in standard configuration and especially when tuned for increased performance, was popular in café racers such as Tribsas and particularly Tritons.