R 21RX & 21XM Crankshaft Ball Bearing - OS23930000 for O.S. Engine  [OS23930000]

Precision crankshaft bearing for engine rebuilds

This replacement crankshaft ball bearing is an RC-scale accessory intended for use with O.S. Engine R 21RX and 21XM engine variants as listed in the product name. It supports crankshaft rotation, lowers friction, and helps maintain shaft alignment under throttle changes and running loads.

Installation notes: check the crankcase and bearing seats for burrs or contamination before installing the bearing, use a proper bearing driver or an even press-fit tool to avoid damage, and verify endplay and free rotation once fitted. For routine checks, confirm the bearing runs smoothly and replace it if you notice roughness or excessive play.

A targeted replacement part for engine rebuilds and maintenance, this bearing restores correct bearing fit and crank alignment to help return engine performance.