Boxer Engine

A boxer engine is a flat engine with cylinders laid horizontally on opposite sides of the crankshaft. In a boxer, opposing pistons move in and out at the same time, like boxers' fists punching towards each other, which gives the name.

The layout is naturally well balanced and smooth, has a low centre of gravity and, with the cylinders sticking out into the airflow, cools well. BMW has built boxer twins since 1923, and they remain the brand's signature engine. Honda's Gold Wing uses a flat-six, and the Soviet-era Ural and Dnepr also use boxer twins.

The protruding cylinders reduce cornering clearance and are exposed in a fall, so cylinder head guards are a popular accessory. Valve clearances on older boxers are easy to reach and check, which owners appreciate.