1976 Triumph Bonneville 650 T120RV

The T120RV Bonneville was a British-built air-cooled, OHV, vertical-twin 650 cc roadster with a 5-speed transmission. Prior to 1976, all British and European foot-shifted motorcycles used right-hand shift. The 1976 Bonneville was the first European motorcycle to use left-hand shift. The modification was made to meet U.S. regulations.

For 1976, engine mods were few. A new muffler set was employed using almost cylindrical reverse-cones (very little taper) with some noise reduction revisions. The twin 30 mm Amal Concentric carburetors were now being produced by the company's Spanish subsidiary and now featured longer ticklers. New petcocks were now clearly marked with 'ON' and 'OFF' to meet new US regs. To mute intake noise, silencer tubes were installed in the centers of each air filter.

But the biggest change on the 1976 Triumph Bonneville surely was the switch from right-hand shift to left-hand shift; again to meet US legislation. This was accomplished with a cross-over shaft, crooked to clear the clutch, which extended through the gearbox and into the center of the primary case, between the clutch & the engine sprocket. From there it passed through the primary cover (a new piece) where it mounted the shifter on its splined end. This all required new inner & outer gearbox covers, bushings, gearbox quadrant, kickstart shaft & primary cover.

When the shifter moved to the left, the brake pedal moved to the right. Rather than work up a new linkage for the rear brake, Triumph took this opportunity to introduce a hydraulic disk brake. The underslung Lockheed caliper was operated via a remotely-operated master cylinder hidden under the seat. Both front & rear disk brakes were identical 10" cast iron units.

Frame modifications were restricted to those needed to accommodate the new rear disk brake & right-hand brake. The frame remained as a “oil-in-frame” model. While regs were heating up in the US, this same year the UK dropped its age-old requirement for a front license plate on motorcycles, the typical ones you saw on front fenders. So the front fenders were no longer drilled for them. Switchgear was now labeled, with the left hand control displaying cast-in labels, while the right hand control and the headlight shell had cheesy stick-on labels that fell off.

Very few Triumph motorcycles were built in 1974 and 1975 due to a factory worker strike. Production increased in 1976 after Triumph employee bought out the company and formed the Meriden Co-op. The Meriden Co-op struggled, and as they were just getting the assembly line rolling again, very few changes were made unless absolutely necessary to meet pending regs. Hence the color combos remained as they were in 1974 & 1975 for part of the year, with Photochromatic Red & Cold White for US & UK markets and Photochromatic Blue & Cold White as a UK option. After 25 years of service, the 650 cc Bonneville was discontinued; only the 750cc T140 remained.


T120RV Bonneville: 5-speed 650 roadster

T140RV Bonneville: 5-speed 750 roadster

Engine type: air cooled, OHV, vertical twin

Displacement: 649cc and 744 cc (45 ci)

Bore & Stroke: 71 mm X 82 mm (650); 76 mm X 82 mm (750)

Compression: 8.6:1 (650); 9.0:1 (750)

Carburetors: 2 Amal Concentrics R930/9, 30 mm

Ignition: Battery and coil, Lucas

Engine output: 49 hp @ 6200 rpm

Primary drive: 3/8" triplex X 84 lins

Primary sprockets: Engine 29T X Clutch 58T

Clutch: Multi-plate, wet

Gearbox: 5-speed constant-mesh, left-foot shift

Ratios, overall:

1st, bottom: 12.25:1

2nd: 8.63:1

3rd: 6.58:1

4th: 5.59:1

5th, top: 4.7:1

Final drive: 5/5" X .400" X 3/8" chain X 106 links

Final drive sprockets: Gearbox 19T X Rear 47T

Frame type: All-welded, oil-bearing large-tube backbone

Suspension, front: Telescopic fork, hydarulic damping 2 way

Suspension, rear: Swing arm, 2 Girling dampers

Brake, front: 10" disk, 2-piston hydraulic caliper

Brake, rear: 10" disk, 2-piston hydraulic caliper

Tire, front: 3.25" X 19" Dunlop, ribbed

Tire, rear: 4.00" X 18" Dunlop, universal

Fuel capacity: 3 gallon

Wheelbase: 54.5"

Seat height: 32.5 "

Ground clearance: 5"

Weight: 387 lbs