998cc Black Shadow - A fine motorbike

Text: Robert Smith • Photography: Robert Smith

In our motorcycle-besotted, pre-license teen years, my buddies and I traded hyperbole like marbles. A Gold Star would do 90 miles per hour in first gear; a 650 Panther revved so slowly, it only fired once every streetlight; a 500 Velocette would pitch you over the handlebars if it backfired while you were kick-starting it. We knew these things to be true because "real" bikers told us so. But there was one machine no one lied about; they didn't have to. From 1948 until the Vincent Engineering Company produced its last motorcycle in 1955, the 998cc Black Shadow was the fastest production two-wheeler you could buy. Period.

Speed hadn't always been Philip Vincent's main goal. As a Cambridge University student in the 1920s, he designed and patented a pivoted-fork rear suspension featuring springs mounted under the seat. It's the forerunner of every modern motorcycle rear suspension system.

Intent on getting into manufacturing, Vincent bought, with his family's help, the remains of the defunct HRD company. These prestigious initials were those of Howard R. Davies, the only rider ever to win the Senior (500cc) TT riding a Junior (350cc) bike. Achieving this feat in 1921 on an AJS, Davies won the Senior again in 1925 on a 500cc bike of his own manufacture. When Vincent bought the business in 1928, the HRD name was its most valuable asset.

Fate next took a hand. One John Gill commissioned from Vincent a motorcycle that he and Walter Stephens would ride around the world. Stephens quit in Australia and a young engineer, Philip Irving, replaced him. Back in the UK, Vincent and Irving formed the working partnership that would create their greatest motorcycles.

Series A
Market response to Vincent's ingeniously sprung bikes was underwhelming, so he turned to racing, entering a team of proprietary engines made by the London firm of John A. Prestwich, branded as JAP, in the 1934 Senior TT. All retired due to engine trouble, persuading Vincent he needed his own engine. The Irving-designed Series A 500cc singles that arrived late in 1934 were named the Comet and Meteor to denote different tune levels. The high-camshaft single used external hairpin valve springs, iron head and barrel, and a Burman gearbox. The 84mm x 90mm bore and stroke would be common to all Vincent motorcycles.

Though his contributions were many, Irving's stroke of genius was realizing a 47-degree V-twin could be built on a modified series A crankcase using the single's "idler" timing gear to drive a second camshaft. The barrels and heads would also fit if the rear cylinder exhausted forward instead of back. Many of the same machine tools could be used. Fanciful accounts suggest a breeze from an open window disturbed the drawings on Irving's desk, laying one over another at the requisite angle. I prefer to think the 998cc series A Rapide was an inspired feat of production engineering.

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For the complete article of the riding impression(s) and technical specifications, please purchase the July/August 2005 back issue.