Needle Bearing Compensation Polini Torsen WD swingarm

What is a Small end bearing?

The small end bearing or piston pin bearing is a needle bearing; the rolling elements used are cylindrically shaped needle rollers. It works similarly to all bearings, reducing friction and increasing the life of the crankshaft and the cylinder.

The small end bearing takes in the piston pin and reduces friction between the piston pin and connecting rod by distributing the load over a larger area.

The small end bearing plays a vital role in the reliability and longevity of the engine, so it is important to replace and lubricate it well each time you reassemble the engine.