Connecting rod

The rod's small end connects to the gudgeon pin and its big end to the crankpin. On small single-cylinder engines the big end usually runs on a needle roller bearing and the rod is replaced together with the crank as a pressed assembly.

• Big-end play makes a deep knocking noise from the bottom of the engine and, if ignored, the rod can break.
• Oil starvation and over-revving are the main causes of rod failure.