Rocker arm

A rocker arm is a small lever that pivots on a shaft in the cylinder head. One end is pushed by the camshaft lobe or, in pushrod engines, by a pushrod; the other end presses on the valve stem and opens the valve. When the cam lobe passes, the valve spring closes the valve again.

Rocker arms let designers place the camshaft away from the valves and can multiply valve lift through the lever ratio. Many motorcycle engines use them, while others have the cam acting directly on bucket tappets or use finger followers, which are a light form of rocker.

Wear on rocker pads, shafts or adjusters changes valve clearance and can cause ticking noises. Check valve clearances at the specified intervals.