| MODEL | TRIUMPH THUNDERBIRD 6T 1950 - 1953 |
| Year | 1950 - 1953 |
| Engine Type | Four-stroke, air-cooled OHV vertical twin |
| Displacement / Capacity | 649 cc |
| Bore X Stroke | 71 x 82 mm |
| Compression Ratio | 8.5:1 (export), 7.0:1 (UK) |
| Cooling System | Air cooled |
| Max Power | 25 kW / 34 hp @ 6500 rpm |
| Max Torque | — |
| Ignition | Lucas magneto (alternator electrics from 1953) |
| Induction | 25 mm Amal Monobloc carburettor (SU MC2 from 1953) |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4-speed constant mesh |
| Clutch | Wet, multi-plate |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Brazed-lug rigid frame (sprung rear hub) |
| Front Suspension | Telescopic fork |
| Rear Suspension | Rigid with sprung hub |
| Front Brakes | 7 in SLS drum |
| Rear Brakes | 7 in SLS drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 775 mm / 31 in |
| Wheelbase | 1403 mm / 55.25 in |
| Ground Clearance | — |
| Dry Weight | 168 kg / 370 lb |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.25 x 19 |
| Rear Tyre | 3.50 x 19 |
| FUEL SYSTEM | |
| Fuel Capacity | 13.6 Litres (US) / 18 Litres (UK and export) |
| Fuel Consumption | — |
| Top Speed | — |
The 6T Thunderbird was Triumph's first 650, created by boring and stroking Edward Turner's 500 cc Speed Twin and aimed at the US market. Early bikes used a rigid frame with the optional sprung hub, a headlight nacelle and deep mudguards. It was a smooth, tractable tourer rather than a sports machine.
