When I first stumbled across this bike it caught my eye because of its weird proportions; low and incredibly compact giving the impression of a short wheelbase with the rider's arse almost directly above the rear axle. Then I noticed exactly what was creating the impression of compactness: a monstrous 500cc, liquid-cooled, SOHC, 8-valve, V-FOUR filling the frame. And it's also got a supercharger bolted on the front for good measure! Pre WW2, every man and his dog were bolting blowers on their GP bikes (and cars) which places this bike as being pre war; it is in fact, the 1939 AJS 500 Supercharged V4.
The 500cc V4 racer was actually based on a road-going air-cooled concept/prototype of 1935. In '39 it became water-cooled and supercharged to compete with the German and Italian machines which were dominating TT and GP racing at the time.
Despite a portly* dry weight of 183 kilos, the 500cc V4, with 55hp at 7,200rpm (@16.5psi boost pressure) could hit a top speed of 216km/h! At this point I'd like to direct your eyes to the pip-squeak drum brake, the plunger rear suspension and tasty liquorice tyres which wouldn't inspire too much confidence on the Isle of Man!
It was a reasonably successful racer to a point. That point was WWII, after which supercharging was banned in Grand Prix racing and a new era had begun. The V4 continued, however, having lost its compressor, its weight hampered its competitiveness.
_______________________*Fat bastard
The ex-Jock West 'Number 2' bike in many of these photos belongs to legendary racer Sammy Miller and can be seen in his famous eponymous museum. If you need proof, above is a photograph of Sammy trying to break the lap record of the museum parking lot! And by the looks of that concentration-face, I bet he did too!
Aaaaand a nice art-deco-ey illustration I found with a 500 V4 in it. Why not!