Vincent’s OHV Comet single is invariably considered the poor cousin of the marque’s series of V-twins that are widely accepted to be the first superbikes of the modern era. But the 31 examples of the Grey Flash racing version built over 1949-50 are a different matter.
The Comet was conceived by Vincent’s Australian designer Phil Irving in 1935, who apparently chose the smallest cylinder bore he could get his hand into to clean the inside! That turned out to be 84mm, which matched to a 90mm stroke delivered 499cc, and these remained the cylinder dimensions of all Vincent twins and singles built up until the company’s demise in 1955. The Comet remained in production through this period, and the success of the high-performance Black Lightning V-twin introduced in 1948 prompted company owner Philip Vincent to attempt the same strategy with his single, resulting in the 1949 Grey Flash.
Unlike the Lightning which was only produced as a racer, the Grey Flash was available in three variants: a stripped-down racer, a road version and a hybrid model which came as a roadbike but, according to the Vincent catalogue, ‘with all the extras necessary for stripping and preparing for racing’.
Heavily based on the Comet, its performance was augmented by porting the cylinder head and fitting bigger valves plus a 32mm Amal carb. Other tuning mods included higher-lift Lightning cams, polished nickel chrome steel conrod and flywheels, a straight-through exhaust, and raising the compression ratio to a heady 8:1. These were combined with a racing magneto and a separate four-speed race gearbox to replace the 3.2kg heavier unit of the roadster.
Chassis modifications entailed stripping off all the Comet’s road equipment, fitting
