Classic and Classy Motorcycles Ltd

Historical Context

The 1978 Triumph Bonneville T140E represented a further development of Triumph’s famous 750cc parallel twin. The T140 had evolved from the earlier 650cc T120 Bonneville and continued the sporting British twin tradition into the late 1970s. The “E” version was introduced to meet increasingly strict emissions requirements, particularly in the important American market. This example has been given café racer styling, reflecting a custom tradition closely associated with Triumph twins since the British café racer movement of the 1950s and 1960s.

Technical Specifications and Performance

• Year: 1978
• Make: Triumph
• Model: Bonneville T140E
• Engine Displacement: 744cc
• Engine Type: Air-cooled OHV parallel twin
• Engine Construction: Unit construction
• Bore and Stroke: 76mm x 82mm
• Carburetion: Twin Amal carburettors
• Starting System: Kick start
• Transmission Type: 5-speed manual
• Gear Change: Left-foot change
• Final Drive: Chain
• Cooling System: Air-cooled
• Frame: Oil-in-frame design
• Braking System: Hydraulic disc brakes front and rear
• Top Speed: Approximately 110 mph depending on specification and condition

Technical Advancements

The T140E incorporated changes intended to make the Bonneville compliant with contemporary emissions regulations while retaining the basic 744cc twin-cylinder design. By this period, the Bonneville also benefited from a 5-speed gearbox, hydraulic disc brakes at both ends and standardised left-foot gear changing. These developments made the later T140 considerably more modern in everyday use than the earlier 650cc Bonnevilles while retaining the traditional air-cooled parallel-twin layout.

Evolution of the Model

The Bonneville began with the 650cc T120 in 1959 and developed into the larger 750cc T140 during the 1970s. The T140E was introduced towards the end of the decade as Triumph adapted the model to changing emissions legislation. Further development of the T140 family brought electronic ignition and, on later versions, electric starting. Despite intense competition from Japanese manufacturers, the Bonneville remained in production into the 1980s and became one of the longest-lived classic British motorcycle designs.

Competitors in the Market

By 1978, the Bonneville competed against increasingly sophisticated motorcycles including the Honda CB750, Suzuki GS750, Kawasaki Z650 and larger Kawasaki Z-series machines. These Japanese motorcycles generally offered multi-cylinder engines and greater refinement, but the Triumph remained considerably slimmer and retained the distinctive handling, sound and mechanical character of a traditional British parallel twin.

Legacy and Appeal

Triumph twins have long been popular foundations for café racer builds, making this 1978 T140E a natural choice for this style of custom motorcycle. Café racers traditionally emphasise a stripped-back appearance, sporting riding position and styling inspired by British road and club racing motorcycles. This example should therefore be viewed as a customised Bonneville rather than a standard factory-specification T140E. The combination of the 750cc Triumph twin and classic café racer styling gives it a strong connection with one of the most enduring traditions in British motorcycling.