| MODEL | BSA A65 THUNDERBOLT 650 1964 - 1972 |
| Year | 1964 - 1972 |
| Engine Type | Four stroke, parallel twin cylinder, OHV |
| Displacement / Capacity | 654 cc / 39.9 cu in |
| Bore X Stroke | 75 x 74 mm |
| Compression Ratio | 9.0:1 |
| Cooling System | — |
| Max Power | 35.8 kW / 49 hp @ 7000 rpm |
| Max Torque | — |
| Ignition | Twin coil |
| Induction | — |
| Start System | — |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4 Speed |
| Clutch | Multi-plate with built-in cush drive |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Steel tubing, cradle |
| Front Suspension | Telescopic forks with coil spring, hydraulically damped |
| Rear Suspension | Coil spring / hydraulically damped |
| Front Brakes | 203 mm / 8 in, drum |
| Rear Brakes | 178 mm / 7 in, drum |
| DIMENSION SPECS | |
| Overall Length | 2060 mm / 81.0 in |
| Overall Width | 711 mm / 28 in |
| Overall Height | 1010 mm / 39.8 in |
| Seat Height | — |
| Wheelbase | 1370 mm / 54.5 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | 177 kg / 397 lb |
| WHEEL SPECS | |
| Front Tyre | 3.25 x 18 in |
| Rear Tyre | 3.50 x 18 in |
| FUEL SYSTEM | |
| Fuel Capacity | 18 Litres / 4.8 US gal (Europe); 9 Litres / 2 US gal (US) |
| Fuel Consumption | — |
| Top Speed | 174 km/h / 108 mph |
The Thunderbolt sat between the mild Star and the hot Lightning, using a single carburettor on the unit-construction 650 twin for a balance of road manners and speed. It gained a concentric carburettor in 1968. It was a straightforward, reliable roadster that sold well in both Europe and the US.
