Layout: Two horizontally opposed cylinders. Benefits: Low centre of gravity, smooth and torquey nature.
BMW is perhaps the most renowned flat-twin (boxer) engine manufacturer, but the heritage of this characterful configuration extends past the German brand’s 92 years of use.
The first motorcycle to sport a flat-twin was a machine called the Fée, later known as the Fairy, built between 1905 and 1907 by the Light Motors Company. At the end of this period the manufacturer went bust and was bought out by Douglas, which went on to utilise the flat-twin technology in its own products.
As with the Fée, the earlier Douglas flat-twin motorcycles (such as the N3) carried their engines in-line with the frame to simplify the connection between the motor’s output and the rear wheel it powered. But as performance increased and greater cooling was needed, manufacturers sporting this configuration took to mounting the twins across the frame to better air the cylinders. Another downside to an engine being in-line with the frame was the need for a longer wheelbase than might otherwise have been desirable.