| MODEL | TRIUMPH TR 65 THUNDER BIRD 1981 |
| Year | 1981 |
| Engine Type | Four-stroke, parallel twin, OHV |
| Displacement / Capacity | 649 cc / 39.6 cu in |
| Bore X Stroke | 76 x 71.5 mm |
| Compression Ratio | 8.6:1 |
| Cooling System | Air cooled |
| Max Power | 31.3 kW / 42 hp @ 6500 rpm |
| Max Torque | 50.1 Nm / 5.1 kgf-m / 37 ft-lb @ 5500 rpm |
| Ignition | — |
| Induction | Single 30 mm Amal carburettor |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 5-speed |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Telescopic fork |
| Rear Suspension | Dual Girling shocks, 5-way preload adjustment |
| Front Brakes | Single 250 mm disc |
| Rear Brakes | 178 mm drum |
| DIMENSION SPECS | |
| Overall Length | 2220 mm / 87.4 in |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 787 mm / 31.0 in |
| Wheelbase | 1422 mm / 56 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 185 kg / 408 lb |
| WHEEL SPECS | |
| Front Tyre | 3.25-19 |
| Rear Tyre | 4.00-18 |
| FUEL SYSTEM | |
| Fuel Capacity | 18.2 Litres / 4.8 US gal |
| Fuel Consumption | 5.2 L/100 km / 45 US mpg / 54 Imp mpg |
| Top Speed | — |
The TR65 Thunderbird was a smaller-capacity, economy-minded Meriden twin built around a short-stroke 650 version of the T140 engine. It offered a five-speed gearbox, a front disc, a light-feeling chassis and a warning-light panel instead of a rev counter, and suited newer riders.
