1969 Triumph T120 Bonneville
Donated to the Museum by the original owner Marty Post
High Performance Air-Cooled 650cc parallel 2-cylinder
Twin Amal Carburetors
Engine design evolved from Edward Turner’s Speed Twin
Side by side cylinder placement promoted air-cooling
The 1969 Triumph T120 Bonneville features a 650cc Twin Cylinder air cooled 4 stroke engine that could compete against larger displacement motorcycles from the US and Europe. Manufactured in Coventry, England, the twin cylinder overhead valve engine was based on Edward Turner’s legendary Speed Twin 500cc engine design, developed in 1937 prior to Turner’s departure to head up BSA.
After Triumph broke the Land Speed Record at 214mph at Bonneville Salt Flats in 1956, the Bonneville ’T120’ name was supposed to hint at its top speed run (as did the Jaguar XK120, of course).
Introduced in 1959, The T120 offered twin carburetors placed behind the cylinders to improve performance over the more sedate single carb T110 Tiger 650 with which it shared many similar parts. Kick starter and gear shift lever were placed on the right-hand side of the machine making it easier to sell in both US and English markets. Oil was carried in a separate oil tank up until 1971 when the frame was modified to serve as the oil reserve tank on the bike. Liberal use of cooling fins covered both cylinders and cylinder head which aided the high output of the bike which could reach speeds upwards of 108 mph in stock trim. Its single downtube frame maximizes engine exposure to the wind for cooling.
Iconic in both style and engineering, the Triumph Bonneville offered speed, light weight and good handling making it a favorite of racing motorcyclists. Triumph 650 motorcycles were found racing in both street and offroad competition with numerous championships to show for it. The stylish bike was also a favorite with the likes of Steve McQueen, Clint Eastwood, Paul McCartney and many other notable owners.
Triumph achieved victory in both 1967 and 69 at the Isle of Man Tourist Trophy road race, winning the production class races. 1967 was the most popular year for Triumph Bonneville sales with 28,000 units sold in the US. Eventually as multi cylinder competition from Asia became available, Triumph added displacement, disc brakes, and improved electricals in the subsequent T140 750cc version of the Bonneville. With declining sales and labor issues in the UK, the T120 650 ceased production in 1975 after a 16-year production run.
Specifications:
Engine: 649cc parallel twin-cylinder 4-cycle, air-cooled, OHV, 360 degree crankshaft, 4-speed transmission, twin Amal Monobloc Carburetors, chain drive
Performance: 46 hp, top speed 108 mph
Chassis: Single downtube tubular steel, telescopic fork front suspension, swing arm rear suspension, drum brakes front and rear
Weight: 402 lbs wet