Grey Flash 2751

The history and restoration of a Vincent HRD Grey Flash

Externally I can see that a considerable amount of the original motor remains. Certainly the cylinder head was replaced. As mentioned earlier in in a comment by Bill Hoddinott: “The original cylinder head of the GF was an unpainted Black Lightning/Shadow front head with standard size but polished valves and the inlet port opened to 32mm to match the carburetor.” We should also assume the barrel utilised now is not the original one. And obviously the piston was changed and the engine lost its special Vibrac connecting rod. Internally I’m eager to see what it looks like and keen to look for markings and stampings in order to ascertain how many of the parts therein, if any, might be original to 2751.

Grey Flash engine numbers explained: ‘F’ = four stroke (engine type), ‘5’ = 500cc (the cubic capacity), ‘A’ = aluminium alloy (material), ‘B’ = bicycle (purpose) and ‘/2B/’ = Grey Flash (the design number). This all precedes the engine number: ‘2751’.

Additional stampings: #1 is at present a bit of a mystery but must be with regards a note on the Engine Spec Sheet (see below). #2 is the mating number – not visible on on the crank case halves until the barrel is removed. #3 are, I believe, inspection stamps. Perhaps readers of this blog could further comment?

‘RH KS’ – not sure what this refers to… Certainly it’s not Right Hand Kick Start. And ’22 TEM’ – this must be the stamping above the engine number… Can anyone shed any light?
The mating number is plainly visible on the inner primary chain case
And the timing chest cover has the HRD logo cast into it so is highly likely to be original to the bike. The vast majority of postwar single cylinder machines produced by the factory are ‘Vincent’ branded and very few timing chest covers were cast with the HRD logo. The mating number stamped onto an inner surface of this cover will confirm originality.

2 thoughts on “The Engine

  1. Somer says:

    Several Flashes were fitted with kick starters. Mine was one.


    1. humphsmith says:

      Yes. This one wasn’t though…


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