Classic and Classy Motorcycles Ltd

Historical Context

The 1979 Triumph 750cc Bonneville, officially known as the T140, represents a late-stage evolution of one of Britain’s most iconic motorcycles. Building on the legacy of the 650cc T120 Bonneville that debuted in 1959, the 750cc T140 was introduced in the early 1970s as Triumph’s answer to increasing competition from Japanese brands offering more power and modern features. By 1979, Triumph had implemented a number of improvements to address reliability and performance while trying to preserve the traditional British character that made the Bonneville name famous. This model year sits near the end of the Meriden Co-operative era, just before Triumph would face major restructuring in the early 1980s.

Technical Specifications and Features

• Year: 1979
• Make: Triumph
• Model: Bonneville T140
• Engine Displacement: 744cc
• Engine Type: Air-cooled, OHV parallel twin, 4-stroke
• Compression Ratio: 8.6:1
• Power Output: Approximately 49 horsepower
• Torque: Around 44 lb-ft
• Transmission: 5-speed manual
• Brakes: Disc front and rear
• Fuel System: Twin Amal carburetors
• Fuel Capacity: 2.5 gallons
• Wheelbase: Approx. 57 inches
• Dry Weight: Approximately 395 pounds
• Key Features: Twin leading-shoe brakes (early disc on many 1979s), classic teardrop tank, dual exhaust, kick-start only (on many UK-spec models).

Project Potential

The 1979 Bonneville is a desirable project for enthusiasts who appreciate traditional British motorcycles. Its straightforward mechanics and wide parts availability make it an accessible restoration. Whether returning it to factory trim or building a period-style café racer or street tracker, the T140’s frame and engine provide a strong base. Keeping it original highlights the Bonneville’s timeless styling—chrome fenders, tank pinstriping, and polished cases—while tasteful upgrades to brakes or ignition can improve usability without detracting from its heritage.

Riding Experience

Once restored, the 750cc T140 Bonneville offers a classic riding experience—engaging, torquey, and full of character. The 5-speed gearbox was a notable improvement over the earlier 4-speed units, giving smoother transitions through the power band. The parallel twin produces a throaty exhaust note and generous torque at low RPMs, making it ideal for laid-back riding or winding B-road routes. The handling is light and nimble, with a balanced frame and traditional British feel. Vibration is part of the experience, reminding riders of the machine's mechanical honesty.

Legacy and Collectibility

The 1979 Triumph Bonneville stands as one of the last "classic" British bikes before major industry changes. Though overshadowed at the time by the technical superiority of Japanese imports, the Bonneville has endured thanks to its styling, mechanical simplicity, and emotional appeal. Today, the T140 is seen as an affordable entry into vintage motorcycling with growing collector interest. Restoring one preserves a pivotal piece of Triumph history—a machine that stayed true to its roots while adapting to a changing world.