| MODEL | TRIUMPH T 120 650 B 1963 - 1964 |
| Year | 1963 - 1964 |
| Engine Type | Four stroke, parallel twin, OHV |
| Displacement / Capacity | 649 cc / 39.6 cu in |
| Bore X Stroke | 71 x 82 mm |
| Compression Ratio | 8.5:1 |
| Cooling System | Air cooled |
| Max Power | 34 kW / 46 hp @ 6500 rpm |
| Max Torque | — |
| Ignition | Lucas MA6 alternator with 2 coils |
| Induction | 2 x Amal 1-1/6" carburettors |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4 speed, constant mesh |
| Clutch | Wet, multiplate |
| Final Drive | Chain, 106 links |
| CHASSIS SPECS | |
| Frame | Single front downtube with second bracing member under tank |
| Front Suspension | Telescopic forks, hydraulic damping |
| Rear Suspension | Swingarm, twin Girling dampers |
| Front Brakes | 8" SLS drum |
| Rear Brakes | 7" SLS drum |
| DIMENSION SPECS | |
| Overall Length | 2020 mm / 85.5 in |
| Overall Width | 720 mm / 28.5 in |
| Overall Height | — |
| Seat Height | 775 mm / 30.5 in |
| Wheelbase | 1403 mm / 55.2 in |
| Ground Clearance | 127 mm / 5.0 in |
| Dry Weight | 165 kg / 363 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.25 x 18, Dunlop Universal |
| Rear Tyre | 3.50 x 18, Dunlop Universal |
| FUEL SYSTEM | |
| Fuel Capacity | 13.6 Litres / 3.6 US gal (US); 18 Litres / 4.8 US gal (UK and export) |
| Fuel Consumption | — |
| Top Speed | — |
For 1963 the Bonneville moved to unit construction with a stiffer, more compact frame braced at the steering head and swingarm, curing the high-speed wobbles of the earlier single-downtube design. An alternator replaced the magneto and wheels went to 18 inch.
