I spotted this JAP (J.A. Prestwich)-engined sprinter at the Brighton Speed Trials in Sept. 2005, and managed to catch a short video when the bike made a run up the strip. British 'Sprints' are the equivalent of American 'Drag Races', but they're racing against the clock only in England, no side-by-side racing, and the film shows several competitors lining up and making a run.
The Brighton event is really worth attending, as the list of machines is invite-only, and the organizers try to cover a range of ages and capacities of cars and motorcycles, from brand-new superbikes to ancient hammers, and the cars range from Vintage Bentleys to newish F1 cars. 2005 happened to be the Centenary of the BST, so the lineup included vehicles which had raced on the seaside from all decades. I should mention that the Brighton event is held on the promenade at the beach, which is normally a pedestrian area full of tourists enjoying the sea and the lousy food. The street level of the town is about 40' higher than the beach, so it's possible to watch the vehicles take their speed runs from above. The second video shows the bikes and cars making their way to the start line - the run itself covers 1/4 mile. Despite all the new machines taking part, often the fastest machines/riders are decades old - this JAP-engined special is normally one of the top contenders, but was a little off-song that day (although it won it's class).
It's an interesting bike; the engine is a 1100cc ohv JAP v-twin, probably from the 1950's, and was developed for speedway sidecar racing and use in Formula 3 cars (eg, Coopers). The engine is housed in a nickel-plated Norton Wideline Featherbed frame, which may well have originally housed a Manx engine - the wheels are certainly magnesium items from a Manx, and the gearbox is a pre-1952 Norton item as well. Sparks are courtesy of two BTH TT magnetos, and the carbs are two whopping 1 1/4" GP items with giant SU float chambers (courtesy of some car, no doubt). The bike would make an awesome road special!
