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

piston engine A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more Reciprocating motion, reciprocating pistons to convert high temperature and high pressure into a Circular motion, rotating motion. This article ...

with one

cylinder A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

. This engine is often used for

motorcycle A motorcycle (motorbike, bike; uni (if one-wheeled); trike (if three-wheeled); quad (if four-wheeled)) is a lightweight private 1-to-2 passenger personal motor vehicle Steering, steered by a Motorcycle handlebar, handlebar from a saddle-style ...

motor scooters A scooter (motor scooter) is a motorcycle with an underbone or step-through frame, a seat, a transmission that shifts without the operator having to operate a clutch lever, a platform for their feet, and with a method of operation that emph ...

motorized bicycle A motorized bicycle is a bicycle with an motor or engine and transmission used either to power the vehicle unassisted, or to assist with pedalling. Since it sometimes retains both pedals and a discrete connected drive for rider-powered propu ...

go-kart A go-kart, also written as go-cart (often referred to as simply a kart), is a type of small sports car, close wheeled car, open-wheel car or quadracycle. Go-karts come in all shapes and forms, from non-motorised models to high-performanc ...

all-terrain vehicle An all-terrain vehicle (ATV), also known as a light utility vehicle (LUV), a quad bike or quad (if it has four wheels), as defined by the American National Standards Institute (ANSI), is a vehicle that travels on low-pressure tires, has a seat ...

s, radio-controlled vehicles,

power tool A power tool is a tool that is actuator, actuated by an additional engine, power source and mechanism (engineering), mechanism other than the solely manual labour, manual labor used with hand tools. The most common types of power tools use electric ...

s and garden machinery (such as

chainsaw A chainsaw (or chain saw) is a portable handheld power saw, power saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. Modern chainsaws are typically gasoline or electric and are used in activities such as t ...

lawn mower A lawn mower (also known as a grass cutter or simply mower, also often spelled lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a lawn, grass surface to an even height. The height of the cut grass may be fixed by ...

cultivator A cultivator (also known as a rotavator) is a piece of agricultural machinery, agricultural equipment used for secondary tillage. One sense of the name refers to frames with ''teeth'' (also called ''shanks'') that pierce the soil as they ar ...

s, and

string trimmer A string trimmer, also known by the portmanteau strimmer and the trademarks Weedwacker, Weed Eater and Whipper Snipper, is a garden power tool for cutting grass, small weeds, and groundcover. It uses a whirling monofilament line instead of a b ...

s). Single-cylinder engines are made both as 4-strokes 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 of the piston, one up and one down, in one revolution of the crankshaft in contrast to a four-stroke engine which ...

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 A flywheel is a mechanical device that uses the conservation of angular momentum to store rotational energy, a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, a ...

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 the opposite direction to each other, which generates a net vertical force ...

s than multi-cylinder engines, as well as more extreme methods such as a dummy connecting rod (for example the Ducati Supermono). 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 Gasoline (North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When formul ...

(and use a

four-stroke cycle 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 ...

), 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 In internal combustion engines, a split-single design is a type of two-stroke engine, two-stroke where two cylinders share a single combustion chamber. The first production split-single engine was built in 1918 and the design was used on several ...

makes use of two pistons which share a single combustion chamber.

Uses

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

Early

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

s 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, a transmission that shifts without the operator having to operate a clutch lever, a platform for their feet, and with a method of operation that emph ...

auto rickshaw An auto rickshaw is a motorized version of the pulled rickshaw or cycle rickshaw. Most have three wheels and do not tilt. They are known by many other terms in various countries, including three-wheeler, Adaidaita Sahu, Keke-napep, Maruwa, auto, ...

s, and

radio-controlled model A radio-controlled model (or RC model) is a model that is steerable with the use of radio control (RC). All types of model vehicles have had RC systems installed in them, including ground vehicles, boats, planes, helicopters and even submarine ...

s. From 1921 to 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

s. The

Honda Super Cub The Honda Super Cub (or Honda Cub) is a Honda underbone motorcycle with a four-stroke engine, four-stroke single cylinder engine, single-cylinder engine ranging in engine displacement, displacement from . In continuous manufacture since 1958 wit ...

(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

sportbike A sports motorcycle, sports bike, or sport bike is a motorcycle designed and optimized for speed, acceleration, braking, and cornering on asphalt concrete race tracks and roads. They are mainly designed for performance at the expense of comfo ...

s (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 have used four-stroke single cylinder engines since the class replaced two-strokes in

2012 2012 was designated as: *International Year of Cooperatives *International Year of Sustainable Energy for All Events January *January 4 – The Cicada 3301 internet hunt begins. * January 12 – Peaceful protests begin in the R ...

Other single-cylinder engines

Engines of other sorts, like the

beam engine A beam engine is a type of steam engine where a pivoted overhead Beam (structure), beam is used to apply the force from a vertical piston to a vertical connecting rod. This configuration, with the engine directly driving a pump, was first used b ...

and certain types of

Stirling engine A Stirling engine is a heat engine that is operated by the cyclic expansion and contraction of air or other gas (the ''working fluid'') by exposing it to different temperatures, resulting in a net conversion of heat energy to mechanical Work (ph ...

, operate using one cylinder and thus can also be considered single-cylinder engines.

References

{{Authority control Motorcycle engines Engines by cylinder layout