A V-twin engine, is a two cylinder internal combustion engine where the cylinders are arranged in a V configuration.
Most engine manufacturers use the classic shared crank pin design. Some notable exceptions include the Moto Guzzi 500cc with 120° V angle and 180° crank pin offset that Stanley Woods rode to win the 1935 Isle of Man Tourist Trophy; the 1983 Honda Shadow 750, claimed as being the first V-twin with an offset-dual-pin crankshaft; and the 1987 Suzuki VX 800, 45° V angle with 45° crank pin offset in USA and 75° crank pin offset for the rest of the world.
Generally, any two-cylinder motorcycle engine with its two cylinders arranged more than 0° and less than 180° apart is referred to as a V-twin. The V-twin engine is not designated by a specific angle, but is often associated with narrow V angles of 42° to 50° as the classic V-twin configuration. Any narrower could cause unwanted vibration, any wider and the chassis would have to be too long.
A 90° twin engine, such as the signature Ducati engine — with the front cylinder approximately horizontal and the rear cylinder approximately vertical — is generally referred to by Ducati as a "L"-twin engine. There is no technical distinction between V-twin and L-Twin engines. These are merely names used by convention.
When comparing common shared crank pin designs, the 90° V angle acts as a counterweight to provide primary balance to the engine, but the firing is uneven. Smaller angles give poorer mechanical balance, but more even firing for a four-stroke (but, even less even firing for a two-stroke).
The terms longitudinal engine and transverse engine are most often used to refer to the crankshaft orientation, however, some sources, most prominently Moto Guzzi, use the terminology in the opposite way.
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