| MODEL | VELOCETTE VIPER 1956 - 1968 |
| Year | 1956 - 1968 |
| Engine Type | Four stroke, single cylinder, OHV |
| Displacement / Capacity | 349 cc / 21.3 cu in |
| Bore X Stroke | 72 x 86 mm |
| Compression Ratio | 8.0:1 |
| Cooling System | Air cooled |
| Max Power | 25 kW / 28 hp @ 7000 rpm |
| Max Torque | — |
| Ignition | Belt-driven dynamo; Lucas system after 1962 |
| Induction | — |
| Start System | Kick start |
| TRANSMISSION SPECS | |
| Lubrication | Wet sump |
| Gear Box | 4 Speed constant mesh, close ratio |
| Clutch | Dry, three-plate |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Telescopic fork with hydraulic compression and rebound damping |
| Rear Suspension | Woodhead-Monroe springs with hydraulic damping, later Armstrong and Girling, adjustable |
| Front Brakes | 7.5 x 1.5 in drum |
| Rear Brakes | 7 x 1 in drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | 1353 mm / 53.25 in |
| Ground Clearance | — |
| Dry Weight | 165 kg / 364 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.25 x 19 in |
| Rear Tyre | 3.25 x 19 in |
| FUEL SYSTEM | |
| Fuel Capacity | 13.6 Litres / 3.6 US gal |
| Fuel Consumption | — |
| Top Speed | 146 km/h / 91 mph |
The Viper was the 350 cc sister to the Venom, developed from the MAC and sharing its bottom end with the 500. It had a bi-metal cylinder with iron liner, a high-compression piston and light alloy head, with plenty of chrome. From 1962 it wore glass-fibre enclosure panels, which traditional Velocette single owners mostly disliked.
