This very rare racer was the lightest model in the range but by no means the least powerful: it was faster than the 350 cc IOE single and almost as fast as the 500 cc IOE twin.
It had a special engine from which the top half was converted to full overhead valve construction. Noticeable in this construction was that the pushrods had a cross-action and that the inlet channel was facing downward, suggesting that the cylinder head was a development from the V-twin OHV racer.
The valves had double springs to counteract possible valve float at high engine revolutions. The “Franconi” label given to these models refers to the famous Swiss racer Francesco Franconi, who seems to have been involved in the development of these fast singles.
The front forks is produced by Brampton special for the 250cc and 350cc racers. Further the motorcycle has Amac carburettor, Best&Lloyd mechanical oil pump and 3-speed Sturmey Archer hand-change gearbox.
The spark comes from a Bosch FF1 Magneto and the tyres are 26×2,5.
The light and agile machine is a rare survivor, only a limited number of these semi-racers have been produced.