page_title: Straight-twin engine
section_title: Motorcycle use
hierarchical_section_title: Straight-twin engine / Motorcycle use
caption_attribution_description: Norton Commando MKIIA, built September 1973 according to the manufacturer's plate. The motorcycle is missing the lower stay on the front mudguard and the silencers are not original, being the "pea-shooter" type fitted to earlier models. An after-market oil cooler is fitted between the front down tubes of the frame, in front of the engine.
context_page_description: A straight-twin engine, also known as straight-two, inline-twin, vertical-twin, or parallel-twin is a two-cylinder piston engine which has its cylinders arranged side by side and its pistons connected to a common crankshaft. Compared to V-twins and flat-twins, straight-twins are more compact, simpler, and usually cheaper to make, but may generate more vibration during operation.
  Straight-twin engines have been primarily used in motorcycles, but are also used in automobiles and in powersports applications. Automobiles with straight-twin engines are usually very small and include city cars and kei cars. Recent examples of cars with straight-twin engines include the Tata Nano and Fiat Group automobiles using the TwinAir engine. Powersports applications include use in outboard motors, personal water craft, all-terrain vehicles, snowmobiles, and ultralight aircraft.
  Different crankshaft angles are used in four-stroke straight-twins to achieve different characteristics of firing intervals and engine balance, affecting vibrations and power delivery. The traditional British parallel twin had 360° crankshafts, while some larger Japanese twins of the 1960s adopted the 180° crankshaft.
caption: Norton Commando Interstate, a motorcycle with a parallel-twin engine
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