A single-cylinder engine, sometimes called a thumper, is a

piston engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...

with one cylinder. This engine is often used for motorcycles, motor scooters, go-karts, all-terrain vehicles, radio-controlled vehicles, portable tools and garden machinery (such as lawnmowers, cultivators, and string trimmers). Single-cylinder engines are made both as

4-stroke A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...

s and

2-stroke A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of t ...

Characteristics

Compared with multi-cylinder engines, single-cylinder engines are usually simpler and compact. Due to the greater potential for airflow around all sides of the cylinder,

air cooling Air cooling is a method of dissipating heat. It works by expanding the surface area or increasing the flow of air over the object to be cooled, or both. An example of the former is to add cooling fins to the surface of the object, either by maki ...

is often more effective for single cylinder engines than multi-cylinder engines. This reduces the weight and complexity of air-cooled single-cylinder engines, compared with liquid-cooled engines. Drawbacks of single-cylinder engines include a more pulsating power delivery through each cycle and higher levels of vibration. The uneven power delivery means that often a single-cylinder engine requires a heavier flywheel than a comparable multi-cylinder engine, resulting in relatively slower changes in engine speed. To reduce the vibration level, they often make greater use of

balance shaft Balance shafts are used in piston engines to reduce vibration by cancelling out unbalanced dynamic forces. The counter balance shafts have eccentric weights and rotate in opposite direction to each other, which generates a net vertical force. Th ...

s than multi-cylinder engines, as well as more extreme methods such as a dummy connecting rod (for example the

Ducati Supermono The Ducati Supermono is a lightweight, single-cylinder racing motorcycle made by Ducati and named after the Supermono racing class. 65 Supermonos were built by Ducati between 1993 and 1995. Technology This lightweight, compact racer was built wi ...

). These balancing devices can reduce the benefits of single-cylinder engines regarding lower weight and complexity. Most single-cylinder engines used in motor vehicles are fueled by petrol (and use a four-stroke cycle), however diesel single-cylinder engines are also used in stationary applications (such as the Lombardini 3LD and 15LD). A variation known as the split-single makes use of two pistons which share a single combustion chamber.

Uses

Detail view of a large single-cylinder air-cooled motorcycle engine

Early motorcycles, automobiles and other applications such as marine engines all tended to be single-cylinder. The configuration is almost exclusively used in portable tools, along with garden machinery such as lawn mowers. Single cylinder engines also remain in widespread use in motorcycles,

motor scooter A scooter (motor scooter) is a motorcycle with an underbone or step-through frame, a seat, and a platform for the rider's feet, emphasizing comfort and fuel economy. Elements of scooter design were present in some of the earliest motorcycles ...

s, go-karts, auto rickshaws, and radio-controlled models. From 1921-1960, the Lanz Bulldog tractor used a large horizontally-mounted single cylinder two-stroke engine. However they are rarely used in modern automobiles and tractors, due to developments in engine technology. Single cylinder engines remain the most common engine layout in

s and low-powered motorcycles. The Honda Super Cub (the motor vehicle with the highest overall sales since its introduction in 1958) uses a four-stroke single-cylinder engine. There are also several single-cylinder sportbikes (such as the KTM 690 Duke R), dual-sport motorcycles (such as the BMW G650GS) and the classic-styled Royal Enfield 500 Bullet. The Moto3 class in the

MotoGP World Championship Grand Prix motorcycle racing is the premier class of motorcycle road racing events held on road circuits sanctioned by the Fédération Internationale de Motocyclisme (FIM). Independent motorcycle racing events have been held since the start of ...

have used four-stroke 250cc (15.2 cu in) single cylinder engines since the class replaced 125cc two-strokes in

2012 File:2012 Events Collage V3.png, From left, clockwise: The passenger cruise ship Costa Concordia lies capsized after the Costa Concordia disaster; Damage to Casino Pier in Seaside Heights, New Jersey as a result of Hurricane Sandy; People gather ...

References

{{Authority control Motorcycle engines Engines by cylinder layout

Characteristics

Uses

See also

References