SOHC (single overhead camshaft)

SOHC stands for single overhead camshaft: one camshaft in each cylinder head (or bank of cylinders) operates both intake and exhaust valves, usually through rocker arms. It sits between OHV pushrod engines, where the camshaft is down in the block and works the valves through pushrods (sometimes loosely called 'single overhead valve'), and DOHC engines with separate intake and exhaust camshafts.

SOHC engines are compact, simple and have fewer parts than DOHC, which suits many singles, commuter bikes and some twins. DOHC layouts allow higher revs and more freedom in valve timing, which is why most high-performance engines use them.

Maintenance is similar for all layouts: check valve clearances and the cam chain or belt at the specified intervals.