Les motos anglaises d'avant 1983

A 77 x 80 mm "short stroke" version of the engine was planned to be used, but this was still in development so the existing 73 x 89 mm "long stroke" engine was retained. High compression 10.5:1 Omega pistons were fitted, the crank lightened and head reworked. A 3S cam was used with steel pushrods. Larger 33 mm Amal Concentric carburettors were fitted and the engine produced 76 bhp (57 kW) at 7,200 rpm.


https://en.wikipedia.org/wiki/John_Player_Norton