Ever heard of the legend of the HRD Vincent Black Shadow? Considering its rarity and the fact that it dates back to the 1940s and ‘50s, that would not be surprising.

The legend has it that in 1948, a British-built HRD Vincent Black Shadow motorcycle, taken straight out of the shipping crate, could do 125 miles per hour. That same year, the first year in production, a Black Shadow was clocked at 150 mph on the Bonneville Salt Flats. In 1956 a Vincent in New Zealand set a new FIM (International Motorcycling Federation) record at 186 mph.

And, probably due to its significantly ‘under-square,’ long stroke (80 X 90 mm) engine, folklore also recalls that at 120 mph every power stroke of this 60.9 cu in 50° OHV V-twin was measured in the distance between light poles – referring to the low-revving nature of the ‘bike, where its 55 horsepower arrived at 5,500 RPM.

Of course, the undeniable performance of the HRD Vincent Black Shadow underpinned the legend, but what made this such a special motorcycle?

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This Is What Gave The HRD Vincent Black Shadow Its Legendary Speed

The Vincent Black Shadow Engine Powered The World's Fastest Motorcycle
Via: BSK SpeedWorks

The engine in the Black Shadow was basically the same air-cooled, dry-sump, four-stroke 50° V-twin engine that powered the standard Vincent Rapide.

Each cylinder's two overhead valves are operated through rocker arms and short pushrods activated by two gear-driven cams mounted high in the engine's timing case. The valves have both upper and lower guides, and the rocker arms are forked at the valve end to operate the valve by pushing on a metal shoulder partway along the length of the stem.

What set the Black Shadow apart from other motorcycles was the careful selection of engine parts, which were picked from normal Rapide production parts. The camshafts, for example, were standard Rapide components, albeit with tighter tolerances, and airflow was improved by blending and polishing the engine's ports.

Because of the low octane rating of the 'Pool' petrol of the period, all Vincents had ridiculously low compression ratios. Although the prototype Black Shadow was built with a static compression ratio lower than the Rapide's nominal 6.8:1, production Shadows were bumped up to 7.3:1.

While other motorcycles of the period were mostly polished and chromed, company founder, Philip Conrad Vincent, decided that the Black Shadow’s engine should be black. So, in order to achieve the engine's signature black finish, a "pyluminising" coating of chromate anti-corrosion primer was applied, over which a layer of Pinchin & Johnson black enamel was added. The part was then baked in an oven for 2 hours at 200 °F.

Although some have claimed that the black finish increased the rate of heat rejection from the engine, its main real benefit seems to have been its visual impact.

As was the norm for Vincents, the Black Shadow’s engine was mounted as a stressed member of the chassis, eliminating the need for a downtube cradle. Series B and C Black Shadows also used the upper frame member as an oil tank. Thanks to such innovative engineering and the extensive use of aluminum alloy the HRD tipped the scales at a slim 458 lb.

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Long After Production Ended The Legend Of The HRD Vincent Black Shadow Lives On

The JMC NORVIN Lives Up To The HRD Vincent Legend
Via: Classic Bike Guide

Paying testament to the Vincent’s sound and innovative engineering, several HRD inspired motorcycles have made well-publicized, if short, appearances since the closure of the factory in 1955.

The most well-known of these being the Norvin that used a Norton Featherbed frame. This evolved into the Somerton Viscount 998 cc, which was a Norvin with Manx Norton frame, swinging arm, and wheels with Norton roadster 'Roadholder' front forks.

Whereas most Vincent-derived successors were one-off builds, an early attempt at production was announced by Staffordshire engineer Tom Somerton in late 1959, with an intended low-volume run from 1960, although it's not known how many were completed.

So, after lying dormant for 40 years, in October 2002 a press release made motorcycle enthusiasts around the world sit up with a jolt. Announcing the return of the Vincent Black Shadow, self-made millionaire and long-time Vincent aficionado, Barney Li, whipped the covers off five prototype motorcycles: a ‘Phase 1’ machine based on the Black Lightning, and four modern interpretations - including the Black Shadow.

The modern bikes with their distinctive, low-slung Vincent look, featuring a large vintage-style headlight were to be built by Roush, using Honda’s RC51 fuel-injected V-Twin, pumping out around 136 horsepower. The Vincent legend was so strong that Honda was prepared to sell its engines to the American maker. However American investors were (rightly) uncomfortable with the idea of a Japanese motor in a resurrected Vincent.

Amongst all the turmoil Li took a breather and began scouting around for alternatives. Unfortunately, his dream of creating a modern Vincent ended tragically when he died while out on a ride in Eastern Arizona in May 2008.

Later that year David Hailwood, Mike Hailwood's son, and bike restorer John Mossey began offering new Norvins under the branding of Hailwood Motorcycle Restorations. With the subsequent dissolution of the business, Mossey continued to sell the Norvin branded as JMC Classics and even added a Fritz Egli-framed model to the ‘lineup’.

With such a rich history it is no wonder that the legend of the HRD Vincent being the world's fastest motorcycle lives on. But with only 11,000 built after the war, 7,000 of which are known to exist, the bloodline is fading fast.