Crankshaft Bearing Wear and Corundum Abrasive

This is the surface of a worn crankshaft bearing as a result of using corundum abrasive paper to clean the valves in this engine. The corundum also does damage to the cylinders but if finally causes failure in the bearings. A corundum abrasive particle can still be seen stuck in one end of one of the groves carved by that particle.