Overhead cam (OHC, SOHC, DOHC)

In an overhead cam (OHC) engine the camshaft sits in the cylinder head above the valves, driven by a chain, belt or gears from the crankshaft. With fewer moving parts between cam and valve than in a pushrod engine, the valvetrain is lighter and stiffer, so it can rev higher and make more peak power.

A SOHC (single overhead cam) engine has one camshaft per cylinder bank, usually working the valves via rockers. A DOHC (double overhead cam) engine has separate intake and exhaust camshafts, typically acting on bucket tappets or finger followers. Almost all modern motorcycle engines are OHC.

Key maintenance points are valve clearance checks at the specified intervals and the cam chain and tensioner. A rattling cam chain on start-up is a common warning sign.