Triumph 1961 T 120 “Bonneville” 649 cc ohv twin frame # D 13509 engine # D 18509
The Bonneville owes its creation to the 1937 Triumph Speed Twin, designed by Edward Turner. This breakthrough design served as a blueprint for future classic British motorbikes. Public demand for more power increased every year and in 1949, Turner upgraded the bike to become the 1950 6T Thunderbird.
During the 1950s, Triumph racked up a number of victories on the Bonneville Salt Flats in the US. For example, in 1955, Johnny Allen rode his Triumph streamliner to 193.30 mph, setting the record for the world’s fastest motorbike. The next year, he outdid his record and came in at 214.17 mph. Bolstered by this success, Triumph introduced the Bonneville in 1959. Based on the Triumph Tiger T110 and designated the T120. It was Turner’s last design before he retired. It had a 649cc parallel-twin engine that gave it the distinction of being the fastest motorbike in the world at the time. However, Triumph miscalculated the US market. The Bonneville had a clunky headlight and valanced fenders, making it more suited to changeable British weather. America wanted a stripped down bike, so Triumph tweaked the 1960 version to be more appealing.
The name ‘Bonneville’, chosen in honour of Johnny Allen’s record-breaking 214-mph record run with his Triumph-powered streamliner at the eponymous Utah salt flats, was an inspired piece of marketing. Triumph lost no time in capitalising on its technical breakthrough, announcing a new model equipped with the ‘splayed’ head and twin Amal carburettors in September 1958: the Bonneville. Testing a T120 ‘Bonnie’ , Motor Cycling found that Triumph’s range-topping sportster possessed abundant vitality. “With exceptional top-end performance goes extraordinary vigour and tractability at low and medium speeds – a combination which makes it perhaps the fastest point-to-point roadster produced in Britain today.”
As well as the performance-enhancing top end, the Bonneville, together with the rest of Triumph’s twins, incorporated a new, stronger crankshaft assembly that development had shown was necessary to cope with the increased power. The latter now stood at 46bhp, an improvement of some 15% over that of the contemporary single-carb T110. Works tester Percy Tait had achieved 128mph at MIRA on a development bike, and even though this figure proved beyond the reach of the production version, the Bonnie was at least as fast as the opposition and much better looking, which was all that mattered.
The 1961 brochure stated: “with the highest performance available today from a standard fully equipped production motorcycle, the Triumph Bonneville 120 is intended primarily for the experienced rider. The two-carburettor engine with splayed port light alloy head, although tremendously powerful, is smooth and tractable at low speeds. The duplex frame provides handling of the highest order.”
This Bonneville is an older restoration with current Dutch registration. She comes with Lucas competition magneto, parcel grid on petrol tank, Smiths 8,000 rpm rev counter and 140 mph speedometer.