Coventry teamsters Nigel Boocock and John Harrhy gave the new BSA 499cc engine a real pounding during a hundred lap try-out, and it came through totally unscathed.
Housed in a Rob North frame and driven through a North-Greenwood countershaft assembly, it was a project of the BSA engineering company under the guide of Engineer works manager Cyril Haliburn.

The tests were originally carried out on the MK1 Prototype (Left) adapted from a B50 Motocross engine. Modifications included sawing off the gearbox whilst the Cylinder barrel was shortened slightly to provide a 13.6 to 1 compression ratio suitable for dope fuels.

Shortly afterwards, the MK2 (Below) was introduced and in the same frame it weighed a total of 179lbs. The main visible differing feature of the MK2 was the sparse interrupted finning of the barrel.
With the compression ratio remaining at 13.6 to 1, the power output was said to be over 45bhp. Ignition was of the Lucas RITA type which dispensed with contact breakers. Ignition coil and amplifier box are mounted between the engine plates at the rear of the crankcase and together with the necessary battery, are claimed to weigh no more than a magneto.

The original 36mm choke carb was replaced by an Amal 34mm Concentric type and unlike other speedway machines, it had a dry sump-lubrication system with the oil being carried through the frame tubes.

Left is the MK2 unit fitted into a Jawa frame with the battery unit clearly visible behind the timing cover.

So what happened to these machines? .....
Carl Askew visited these Pages and tells us the following.

• "The BSA speedway bikes that you feature that were ridden by Nigel Boocock were owned by Alan Grahame, and he rode his first few races at Birmingham in 1973-74 on both of them. I do not know where they are now."

  "Alan Grahame's dad, Archie was a Sidecar Motocross rider back in the sixties and rode BSA's. He got to be friends with some of the guys there in the racing department. Anyway when the factory was closing down his mate told him to come around and take what he wanted, so he got both the BSA Speedway bikes with a heap of other stuff. He used to ride both of them at different times. They were always very clean and tidy."

Our thanks to Carl for letting us share that story.

To find out more about the B50 and BSA in general Rickard Nebror has an excellent site. [Link missing from archive.]