Cylinder Head

The cylinder head is bolted to the top of the cylinder and seals it, forming the roof of the combustion chamber. A head gasket between them keeps compression, oil and coolant where they belong.

On a four-stroke engine the head contains the intake and exhaust ports, the valves with their springs and seats, the spark plug and on most modern engines one or two overhead camshafts. On a two-stroke the head is a much simpler part with the combustion chamber dome and spark plug hole, since the ports are in the cylinder.

Common head-related problems are leaking head gaskets, warped heads after overheating, worn valve seats and guides, and stripped spark plug threads. Always tighten head bolts in the specified sequence and torque, and let the engine cool before removing the head to avoid warping.