The original Triumph Bonneville was a 650 cc parallel-twin motorcycle manufactured by Triumph Engineering and later by Norton Villiers Triumph between 1959 and 1974. It was based on the company's 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. Initially it was produced with a pre-unit construction engine which enabled the bike to 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 (BSA frame) and particularly Tritons (Norton featherbed frame).