Flat-twin engine
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A flat-twin engine is a two-cylinder internal combustion engine with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the boxer-twin engine, where both pi
Douglas 80 Plus motorcycle engine (circa 1950)
Citroën 2CV engine (viewed from rear)
1912 Douglas N3 engine
1942 Harley-Davidson XA engine
Flat engine
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A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the
Flat-twin engine
…the later model) all these problems were fixed with a rear-domed piston, crankcase mixers and refined ignition system. Most flat-twin engines use a boxer configuration for the crankshaft and are therefore called "boxer-twin" engines. In a boxer-twin engine, the 180° crankshaft moves the pistons in phase…
Benz Contramotor, the first commercial flat-engine design, ca. 1899
1954 BMW R68 flat-twin boxer engine
World War II-era Riedel starter motor
1969 Hino Motors DS140 boxer-twelve diesel engine