A single cylinder engine, colloquially known as a one-lunger (or thumper in case of it being a large four-cycle), is an engine configuration consisting of just one cylinder, the simplest arrangement possible for an Otto or Diesel engine. The mounting can be standing, lying or angled.
Some early automobiles, such as the Cadillac 1906 Model K and 1907 Models L and M used single-cylinder engines . Single cylinder engines were also popular at one time for marine uses (see external links, below). The first Moto Guzzi design used a horizontal single.
In the USA, the most common configuration is the 50cc-two-stroke seen in many bikes and scooters. These vehicles allowed the first mass-motorisation in many countries. Single cylinders are very common in India and China for engines considered small in the USA but a 180cc is considered large elsewhere in the word. In India, the Royal Enfield 350cc and 500cc has been popular for over 50 years for their large size and low reving torque. Most engines used in small portable appliances, such as chainsaws, generators and lawn mowers, usually have one cylinder. Also, the one-lunger is used in working vehicles, motorsports, airplanes, and as an industrial motor.
Suzuki has produced the Suzuki LS650 Savage, a 652cc single cylinder 4-stroke motorcycle, off and on from 1986 to the present, although the content has changed slightly and the motorcycle has been renamed the Suzuki Boulevard S40 .
A Rotax sourced 650cc single cylinder engine was used in the long-lived and highly popular BMW F650GS motorbike. This bike was designed for distance and adventure touring, a usage to which the simplicity of the single cylinder design is well suited. The single cylinder 4 stroke design also typically develops a wide power band, allowing for a more relaxed selection of gears when riding - ideal when touring.
The Guinness Book Of World Records has announced that the world’s largest single cylinder engine for a motorcycle is the 2000 cc engine that was mounted into an old NSU Konsul motorcycle frame, and was built by Franz Langer, a retired engineer living in Germany.