The unusual engine layout was the S7's notable feature with an engine and drive similar to that of a car. The engine was a longitudinally mounted inline vertical OHC 500 cc twin with coil ignition and wet sump lubrication which, through a dry clutch, drove a shaft drive to the rear wheel. The inline engine made this technologically feasible (flat-twin "boxer" engines on BMW motorcycles had already used shaft drives). Unlike BMW, who sensibly specified a bevel gear crown-&-pinion drive to the rear wheel, Sunbeam used worm gearing with a bronze spiral gear; by reputation the soft bronze gave rapid wear of drive components.