O.S. Engine OS4A408000 Drive Washer — Crank Shaft Component  [OS4A408000]

Washer to maintain crank shaft alignment

This O.S. Engine drive washer is manufactured as an RC crank shaft spacer to control axial distance and keep rotating components running true. It serves as a compact replacement or service item commonly used with engine crankshaft sets on small model engines.

Fitting is straightforward for those familiar with engine work: press the washer flat against the mating face of the crank, ensure uniform contact, then confirm axial clearance once assembled. Its function in setup is to maintain correct gear and drive clearances so throttle response and timing stay repeatable.