Ever since the Series-A’s arrival in 1937, the Vincent v-twin had been synonymous with design innovation, engineering excellence and superlative high performance. So in September 1955 when it was revealed that production of the Stevenage-built machines would cease, the news stunned the motorcycling world. It had been decided that the firm’s future lay in more profitable lines of manufacture, and just 100 more of the fabulous v-twins would be completed. By the time its demise was announced, Vincent’s final twin – the Series-D – had been in production for just six months.
It had been Philip Vincent’s belief that provision of ample weather protection combined with enclosure of engine and gearbox, would make the Vincent Series-D the ultimate ‘gentleman’s motorcycle’ and to reflect this change of emphasis the enclosed Rapide and Black Shadow were known as Black Knight and Black Prince respectively. In actuality, delayed delivery of the glassfibre panels – plus continuing demand for traditionally styled models – resulted in over half the production leaving the Stevenage factory in un-enclosed form.
Other Series-D innovations included a new frame and rear suspension; a steel tube replaced the original fabricated upper member/oil tank while the paired spring boxes gave way to a single hydraulic coil-spring/damper unit offering a generous seven inches of suspension travel. In place of the integral oil reservoir there was a separate tank beneath the seat. The user-friendly hand-operated centre stand was a welcome addition, and there were many improvements to the peerless v-twin engine including coil ignition for easier starting and Amal Monobloc carburettors. Sadly though, the Shadow’s magnificent 5″-diameter Smiths speedometer had been replaced by a standard 3″ unit.
Unfortunately for Philip Vincent, his vision of the Series-D as a two-wheeled Grande Routière just did not conform to the public’s perception of the Vincent as the ultimate sports motorcycle. The firm lost money on every machine made, and when production ceased in December 1955 around 460 Series-D v-twins had been built, some 200 of which were enclosed models.
The current vendor purchased this Black Prince, which was in running condition, from Bator International in California, USA in 2007. Expired tax discs on file indicate that the Vincent had previously been registered in the UK, the accompanying V5C Registration Certificate showing that ‘CSU 451’ (almost certainly an age-related mark) had been issued in 1987. Since acquisition, the machine has been started and run, though no work has been carried out.
Report by bonhams.com