BSA 650 ROCKET GOLD STAR A10 RGS

01 Engine

After 12 years of production, the A-series twin design was well refined. The 360-degree, built-up crankshaft was supported by a drive side ball bearing and a bush on the timing side. The one-piece con rods gave a stroke of 84mm topped with 70mm, high-compression pistons for 646cc. Gears drove the single camshaft (usually BSA’s new ‘Spitfire’ performance grind) located behind the cylinders, as well as the magneto. To the front of the timing chest, a chain drove the dynamo. The one-piece iron cylinder casting had separate aluminium cylinder heads.