Classic and Classy Motorcycles Ltd

Historical Context

The 1977 Triumph Bonneville T140 was part of Triumph’s effort to keep pace with rapidly advancing Japanese competition during the 1970s. Building on the legacy of the T120, the T140 featured a larger 750cc engine, improved frame design, and other updates aimed at improving reliability and performance. As traditional British motorcycle manufacturers struggled to modernize, the Bonneville remained a symbol of classic styling, torque-rich parallel twin character, and simplicity. The 1977 model year was a significant point in the T140’s timeline, marking the last of the pre-Bonneville Special (T140D) variants while retaining the distinctive dual-carb setup, kick-start, and classic aesthetics.

Technical Specifications and Features

• Year: 1977
• 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 45 lb-ft
• Transmission: 5-speed manual
• Brakes: Single disc front and rear
• Fuel System: Twin Amal Concentric carburetors
• Fuel Capacity: 2.5 gallons
• Wheelbase: Approximately 57 inches
• Dry Weight: Approximately 395 pounds
• Key Features: Unit construction engine, twin exhausts, classic tank design, and kick-start only (electric start added in later variants).

Project Potential

The 1977 Bonneville T140 makes an excellent restoration candidate for enthusiasts of classic British motorcycles. With strong aftermarket support for parts and a well-documented service history, restoring a T140 to its original specification is achievable for dedicated owners. Many projects aim to retain the vintage styling—chrome mudguards, polished cases, and tank decals—while upgrading reliability with modern ignition or carb tuning. Alternatively, some turn the T140 into a tasteful custom café racer or period-correct street scrambler, using its minimalist frame and timeless engine layout as a foundation.

Riding Experience

Once restored, the T140 delivers a uniquely British riding experience. The torquey twin engine produces ample midrange grunt, making it ideal for relaxed cruising and spirited backroad rides. The 5-speed gearbox provides a more refined ride than earlier models, and the front and rear disc brakes—though basic—offer reasonable stopping power for the bike’s weight and performance. Vibration, typical of classic British twins, adds to the mechanical feel, but thoughtful engine mounts and tuning can reduce fatigue. The kick-start only system on this model year adds an authentic touch that appeals to purists.

Legacy and Collectibility

The Triumph Bonneville T140 represents one of the last truly classic British motorcycles before the brand underwent significant modern redevelopment. The 1977 model is valued for its combination of traditional aesthetics and incremental performance improvements. As appreciation for vintage Triumphs continues to grow, especially among collectors who favor originality and craftsmanship, the T140 has become a desirable model. Restoring a 1977 Bonneville is not only about preserving a motorcycle—it’s about keeping alive one of Britain’s most iconic two-wheeled exports.