Alan Cathcart rides the ex-Jack Ehret Lightning, recently refurbished by marque expert Patrick Godet in Malaunay, France.
1951 Vincent Series C Black Lightning
Engine: 998cc air-cooled OHV 50-degree V-twin, 84mm x 90mm bore and stroke, 13:1 compression ratio, 70hp at 5,600rpm
Top speed: 142mph
Carburetion: Two 32mm Amal 10TT9 with remote float chambers
Transmission: 4-speed, chain final drive
Electrics: Lucas KVF-TT magnesium-body magneto
Frame/wheelbase: Steel monocoque frame with engine as stressed member/56.5in (1,435mm)
Suspension: Vincent Girdraulic girder fork with Vincent hydraulic shock front, Cantilever steel swingarm with single Vincent hydraulic shock and twin separate springs rear
Brakes: Dual 7in (178mm) SLS drum front and rear
Tires: 3 x 21in front, 3.5 x 19in rear
Weight (dry): 360lb (172kg)
More than six decades ago, the Vincent Black Shadow delivered the most performance from a street-legal vehicle that money could buy — on two wheels or four. Officially timed at 122mph, it out-sped the Jaguar XK120 two-seater, then the world’s fastest production car, making the shadow the first true Superbike of the modern era.
The ultimate Vincent was the Series C Black Lightning, a production version of the bike Rollie Free rode to break the AMA’s land speed record in 1948 on the Bonneville Salt Flats. Available only by special order, the standard Black Lightning was supplied in racing trim with a tachometer, Elektron magnesium alloy brake plates, racing tires on alloy rims, rearset foot controls, a solo seat and aluminum fenders. This reduced the Black Lightning’s dry weight to just 360 pounds versus the Black Shadow’s 458 pounds.
The Lightning’s 998cc air-cooled, overhead valve 50-degree V-twin engine was given higher-performance racing components including Mark II Vincent cams with higher lift and more overlap, stronger, highly polished Vibrac connecting rods with a large-diameter caged roller-bearing big end, polished flywheels and Specialoid pistons delivering a 13:1 compression ratio for methanol fuel. The combustion chamber spheres were polished, as were the valve rockers and streamlined larger inlet ports, blended to special adapters and fed by twin 1-1/4-inch Amal 10TT9 carburetors.
The Ferodo single-plate clutch’s cover featured center and rear cooling holes, while the 4-speed gearbox was beefed up to transmit the extra power, at least 70 horsepower at 5,600rpm (versus the Black Shadow’s claimed 55) and a top speed of 150mph.
Order the July/August 2017 issue of Motorcycle Classics to read more about the ex-Jack Ehret 1951 Vincent Black Lightning. Contact Customer Service at (800) 880-7567 or contact us by email.