The two strokes first, intake
and compression, second,
combustion and exhaust.
The two-stroke engine cycle differs from the more common four-stroke cycle by having only two strokes (linear movements of the piston), although the same four operations (intake, compression, power, exhaust) still occur. Thus, there is a power stroke per piston for every engine revolution, instead of every second revolution.
Two-stroke engines are light, mechanically simple and produce more power than a similar size four stroke when running well.
The down sides of a two-stroke are: They are oily and dirty, require regular maintenance, and power is only available in a narrow rpm band, often referred to as the power band.
Two stroke sportbikes like the Aprilia RS250 are well known for their acute handling, lightweight, and narrow powerband, unfortunately they are no longer produced.
Four-stroke engines
Four-stroke engines are by far the most common type of engines found in modern motorcycles. The four-stroke engine operates on the exact same principle as regular car engines except on a smaller scale. Four-strokes are cleaner, more reliable and power comes across a much wider range of rpm than two-strokes.
Engine Configuration
Engines come in a variety of cylinder configurations and numbers. Some general rules which most engines live by are: More cylinders usually allows for a higher maximum rpm. Less cylinders provide more torque at low rpm. And vibrations tend to decrease with more cylinders.
One cylinder, or single cylinder engines as they are commonly known, are just that. One cylinder, usually positioned vertically with a single spark plug attached to the top.
V-twin engine BMW Boxer twin
Two cylinder engines, or twins, are one of the most popular types of motorcycle engine. V-twins are the most common 2 cylinder engines, the cylinders are positioned in a 'V' configuration with both cylinders pointing upwards, V-twin engines power all Harley-Davidson bikes and many sportbikes with 'character'.
L-twin engines power some Ducati motorcycles, this is essentially a V-twin with one cylinder pointing horizontally forward.
Parallel twins exist where the cylinders are positioned parallel to one another.
BMW produces boxer twin (otherwise known as flat twin) engines. In a boxer twin engine the cylinders are opposed to one another and move in a manner similar to a boxers fists.
Three cylinder engines, or triples are less common. However, companys such as Triumph and Benelli have produced several triple engines. Triumph has cornered the market in triples and their newest sportsbike the Daytona 675 Triple is one of the most desirable bikes on the market today.
Four cylinder engines are similar to small car engines, the cylinders are normally positioned in an in-line configuration, where the cylinders are lined up one after another in a line. V and square twin designs have also been produced.
A less conventional motorcycle engine, comes in the MTT Y2K Turbine superbike. This bike is fitted with an aircraft grade jet engine, not a common engine choice for motorcycle manufacturers.
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