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Asingle-cylinder engine, sometimes called athumper, is apiston engine with onecylinder. This engine is often used formotorcycles,motor scooters,motorized bicycles,go-karts,all-terrain vehicles,radio-controlled vehicles,power tools and garden machinery (such aschainsaws,lawn mowers,cultivators, andstring trimmers). Single-cylinder engines are made both as4-strokes and2-strokes.
Compared with multi-cylinder engines, single-cylinder engines are usually simpler and compact.[1] Due to the greater potential for airflow around all sides of the cylinder,air cooling 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.[2] The uneven power delivery means that often a single-cylinder engine requires a heavierflywheel than a comparable multi-cylinder engine, resulting in relatively slower changes in engine speed. To reduce the vibration level, they often make greater use ofbalance shafts than multi-cylinder engines,[3] as well as more extreme methods such as a dummy connecting rod (for example theDucati Supermono).[4][5] 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 bypetrol (and use afour-stroke cycle),[6][7][8] howeverdiesel single-cylinder engines are also used in stationary applications (such as theLombardini 3LD and 15LD).
A variation known as thesplit-single makes use of two pistons which share a single combustion chamber.
Earlymotorcycles,automobiles and other applications such as marine engines all tended to be single-cylinder. The configuration is almost exclusively used in portable tools, along withgarden machinery such as lawnmowers.[9] Single-cylinder engines also remain in widespread use in motorcycles,motor scooters,go-karts,auto rickshaws, andradio-controlled models. From 1921 to 1960, theLanz Bulldog tractor used a large horizontally mounted single-cylinder two-stroke engine.[10] 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 inmotor scooters and low-poweredmotorcycles. TheHonda Super Cub (the motor vehicle with the highest overall sales since its introduction in 1958) uses a 49 cc (3.0 cu in) four-stroke single-cylinder engine. There are also several single-cylindersportbikes (such as theKTM 690 Duke R),dual-sport motorcycles (such as theBMW G650GS) and the classic-styledRoyal Enfield 500 Bullet.[11][12]
The Moto3 class in theMotoGP World Championship have used four-stroke 250 cc (15.3 cu in) single-cylinder engines since the class replaced 125 cc (7.6 cu in) two-strokes in2012.
Engines of other sorts, like thebeam engine and certain types ofStirling engine, operate using one cylinder and thus can also be considered single-cylinder engines.
