Single-cylinder engine

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DKW RT 250 (1952-1953) motorcycle engine 2007-05-20 3 DKW RT 250 in Mendig (kl).JPG
DKW RT 250 (1952–1953) motorcycle engine

A single-cylinder engine, sometimes called a thumper, is a piston engine with one cylinder. They are often used for motorcycles, motor scooters, go-karts, all-terrain vehicles, radio-controlled (on 0) [2974] vehicles, portable tools and garden machinery (such as lawnmowers, cultivators, and string trimmers).



Villiers engine in a 1959 Bond Minicar Bond minicar engine bay 1959.jpg
Villiers engine in a 1959 Bond Minicar

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 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 shafts than multi-cylinder engines, [3] as well as more extreme methods such as a dummy connecting rod (for example the Ducati 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 by petrol (and use a four-stroke cycle), [6] [7] [8] 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.


Yamaha SRX600 (1985-1997) motorcycle engine Detail view of a large single-cylinder air-cooled motorcycle engine.jpg
Yamaha SRX600 (1985–1997) 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. [9] Single cylinder engines also remain in widespread use in motorcycles, motor scooters, 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. [10] However they are rarely used in automobiles and tractors these days, due to developments in engine technology.

Single cylinder engines remain the most common engine layout in motor scooters and low-powered motorcycles. The Honda 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-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. [11] [12]

The Moto3 class in the MotoGP World Championship have used four-stroke 250cc (15.2 cu in) single cylinder engines since the class replaced 125cc two-strokes in 2012.

See also

Related Research Articles

Reciprocating engine Engine utilising one or more reciprocating pistons.

A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.

V6 engine Piston engine with six cylinders in a "V" configuration

A V6 engine is a six-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.

Cylinder bank Line of cylinders in a piston engine arranged in two or more lines

Piston engines are usually arranged so that the cylinders are in lines parallel to the crankshaft. Where they are in a single line, this is referred to as a straight engine.

V4 engine Piston engine with four cylinders in "V" configuration

A V4 engine is a four-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.

Flat-twin engine

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 cylinders move inwards and outwards at the same time.

Flat-four engine

A flat-four engine, also known as a horizontally opposed-four engine, is a four-cylinder piston engine with two banks of cylinders lying on opposite sides of a common crankshaft. The most common type of flat-four engine is the boxer-four engine, each pair of opposed cylinders moves inwards and outwards at the same time.

Straight-twin engine Inline piston engine with two cylinders

A straight-twin engine, also known as an inline-twin, vertical-twin-0=0(2974), or parallel-twin is a two-cylinder piston engine where two cylinders are arranged in a line along a common crankshaft.

Straight-four engine Inline piston engine with four cylinders

A straight-four engine is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.

Straight-six engine Internal combustion engine

The straight-six engine is an internal combustion engine, with six cylinders mounted in a straight line along the crankcase with all the pistons driving a common crankshaft.

Straight-three engine Type of engine

A straight-three engine is a three-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.

Yamaha Motor Company Japanese motorcycle manufacturer

Yamaha Motor Co., Ltd. is a Japanese manufacturer of motorcycles, marine products such as boats and outboard motors, and other motorized products. The company was established in 1955 upon separation from Yamaha Corporation, and is headquartered in Iwata, Shizuoka, Japan. The company conducts development, production and marketing operations through 109 consolidated subsidiaries as of 2012.

Flat-six engine

A flat-six engine, also known as a horizontally opposed-six, is a six-cylinder piston engine with three cylinders on each side of a central crankshaft. The most common type of flat-six engine is the boxer-six engine, where each pair of opposed cylinders moves inwards and outwards at the same time.

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.

Motorcycle engine Engine that powers a motorcycle

A motorcycle engine is an engine that powers a motorcycle. Motorcycle engines are typically two-stroke or four-stroke internal combustion engines, but other engine types, such as Wankels and electric motors, have been used.

Villiers Engineering Historical motorcycle manufacturer

Villiers Engineering was a manufacturer of motorcycles and cycle parts, and an engineering company based in Villiers Street, Wolverhampton, England.

Free-piston engine

A free-piston engine is a linear, 'crankless' internal combustion engine, in which the piston motion is not controlled by a crankshaft but determined by the interaction of forces from the combustion chamber gases, a rebound device and a load device.


Flyscooters, formerly known under the name Znen, was an American company that marketed gas-powered motor scooters manufactured in China and Taiwan. The company was founded in 2006 in Florida by scooter enthusiasts Leon Li and Daniel Pak, and ceased operations in 2010. During the operating life of the company, Flyscooters' basic business model was to import low-cost scooters from abroad and distribute them under the Fly brand name to a network of retail scooter dealerships across the United States, providing dealers with warranty and spare parts support.

Split-single engine

In internal combustion engines, a split-single design is a type of two-stroke where two cylinders share a single combustion chamber.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

Small engine

A small engine is the general term for a wide range of small-displacement, low-powered internal combustion engines used to power lawn mowers, generators, concrete mixers and many other machines that require independent power sources. These engines often have simple designs, for example an air-cooled single-cylinder petrol engine with a pull-cord starter, capacitor discharge ignition and a gravity-fed carburettor.


  1. "Single Cylinder Engines". Retrieved 10 July 2019.
  2. "How to Balancing a Single Cylinder Engine Crankshaft and Piston/Connecting Rod Assembly and Flywheel to Reduce Dangerous Vibration". Retrieved 10 July 2019.
  3. "Engine Science: The Balancing Act of Single Cylinder Engines". Retrieved 10 July 2019.
  4. Methods of Balancing Single Cylinder Engines. Joseph R. Harkness. SAE Transactions. Vol. 77, Section 3: Papers 680436–680591 (1968), pp. 2329-2338
  5. Suzuki's Supermono Engine Design. A second con-rod without a piston. Ben Purvis. April 26, 2019
  6. "5 of the funkiest single-cylinder street bikes". 5 March 2009. Retrieved 7 July 2019.
  7. "The Single Life: 6 of the best thumpers". Retrieved 7 July 2019.
  8. "The 16 Best Retro Motorcycles Make Bikes Great, Again". 9 August 2016. Retrieved 7 July 2019.
  9. "How Car Engines Work". 5 April 2000. Retrieved 10 July 2019.
  10. "The Lanz Bulldog". Retrieved 10 July 2019.
  11. "690 Duke: The essence of motorcycling". Archived from the original on 2012-06-12. Retrieved 2012-06-01.
  12. David Blasco. "Royal Enfield Motorcycles". Archived from the original on 2011-12-07. Retrieved 2011-12-06.