Bonhams Pioneer, Vintage
& Classic Motorcycle Auctions

Bonhams Motorcycle Department


Date Published:
22 Apr 2018
Lancashire, UK

• Matching numbers example • Fully restored • Numerous modern improvements • Custom made petrol tank • Custom made stainless steel exhaust system BSA adapted the B40 engine, increasing the capacity from 350cc to 440cc, creating the B44 incarnation which was used by Jeff Smith to great effect in scrambles competition, winning the World Motocross Championship in 1964 and 1965. It spawned a number of various competition-oriented models, culminating in what was to be the ultimate unit single, the B50, announced in late 1970. It had been stretched to 500cc and was produced in road and off-road versions. All had the new, oil bearing, frame. One of these was the Victor B50MX. This BSA B50 was despatched to the USA in February 1973. After repatriation to the UK it was purchased by the present owner in 2012 (receipt on file). He started a restoration of the machine, utilising various specialists for different aspects of the work. The engine was entrusted to RTS Racing for a complete rebuild (invoice on file) and included a new cylinder liner with nikasil bore, Omega piston, NEB conrod, and balanced crankshaft. The big end bearing, main bearings, cam followers, valves and springs were all replaced. In the gearbox, third gear and one of the selector forks were replaced, and a new NEB clutch and shaft were fitted. A new Electrex World alternator and digital ignition system were used to replace the coil and points. An external oil filter and improved engine breathing were adopted to ensure long term reliability. A wiring harness was made up to run the GPS speedometer, horn and LED running lights in the front number board. The frame was powder coated, the front forks rebuilt using slightly stronger springs, and new Rock Shocks rear shock absorbers were fitted. Terry Weedy fabricated the rear swinging arm, which is stronger and lighter than the original, finished with nickel plating. A bespoke alloy petrol tank was made, polished, painted, then lacquered all over. The petrol tank painting was done by Altamura who airbrushed the 'BSA' motif on the tank. A one-off stainless-steel road-legal exhaust system was made by OS pipes. Wheels were rebuilt with black anodised alloy rims. A new Amal carburettor was fitted, and the seat was recovered. The finished machine was road registered with the number SCA 972L and has covered only a small mileage to date, so will require further running-in by a new owner. Documentation comprises a current V5C, the aforementioned purchase receipt and engine invoice, a BSA Owners' Club dating certificate, and sundry papers.