A single cylinder engine is a type of combustion engine that features only one cylinder, or chamber in which a piston moves to engage combustion. This is the engine's source of power, and since only one piston is doing the work, a single cylinder engine is primarily used on smaller vehicles and tools. It can produce a relatively large amount of power given its size, but this engine is not especially adept at varying the power output quickly, making it less versatile for larger vehicles. These engines are lightweight and compact, making them a good choice for engine powered tools such as weed whackers.
Disadvantages of a single cylinder engine include the vibration the engine is known for producing, as well as the lower power output. Vibration occurs for several reasons; primary among them is the weight of the rotating parts. Since only one cylinder is used for power output, many of the rotating components have to be extra strong to withstand the strain of operation. This means the parts can be quite heavy — much heavier than their counterparts in two- and four-cylinder engines. This rotational weight can cause vibration as the piston activates, which is not too much of a disadvantage on small engines used for weed whackers, chain saws, and so on. It can be a problem on this type of engine mounted to a motorcycle or moped.
One of the biggest advantages of a single cylinder engine is the production cost. Since the engine is relatively small and does not feature several combustion chambers, the engine can be built cheaply and easily, driving down the cost of this effective engine style. These engines are therefore common on lower-end small motorcycles, mopeds, go-karts, and lawnmowers. The engine is also lightweight in most cases, making it easy to manipulate on handheld garden or yard machinery.
Early motorcycle models used single cylinder engine designs as a power source, though the vibration issues made the engine a poor choice, especially in comparison to two- and four-cylinder engines. To counteract the vibration problems, some engines were fitted with balances that sought to steady the vibrating engines, and these worked well, to a point. As motorcycles grew larger and faster, however, the single-cylinders were replaced with larger engines that could power the machine more effectively. Automobiles have also used single cylinder engines in the past, but four-, six-, and eight-cylinder engines are far more common.