page_title: U engine
section_title: Tandem twin engine
hierarchical_section_title: U engine / Variations / Tandem twin engine
caption_attribution_description: Barber Vintage Museum_382 1976 Kawasaki KR250
context_page_description: A U engine is a piston engine made up of two separate straight engines placed side-by-side and coupled to a shared output shaft. When viewed from the front, the engine block resembles the letter "U".
  Although much less common than the similar V engine design, several U engines were produced from 1915-1987 for use in airplanes, racing cars, racing and road motorcycles, locomotives, and tanks.
context_section_description: A tandem twin engine, occasionally used in motorcycles and go-karts, is a two-cylinder engine which uses a similar design to U engines.
  The motor has two crankshafts, one for each cylinder which are joined and kept in co-ordination by load carrying, crank-phasing gears connecting the two cylinders.
  The tandem twin layout is used only with two-stroke engines since these must have a discrete crankcase chamber per cylinder. The prime advantage of a tandem-twin two-stroke is that the engine can be very narrow while allowing chain final drive without a power-wasting 90° turn.
  Between 1975 and 1982, Kawasaki used the design to win four 250 cc and four 350 cc world championships before they retired from Grand Prix racing. The engine design was also used for a road legal production motorcycle inspired by the racer. The Kawasaki KR models were instrumental in establishing the company as a manufacturer of high-performance motorcycles.
  Rotax developed a similar tandem twin design, the model 256, which it sold to independent constructors. The CCM Armstrong 250 cc, Waddon, EMC, Hejira, Decorite, and Cotton racers used this engine. CCM Armstrong developed a 350 cc version of the engine. Aprilia's 1985 GP racing bikes also used the Rotax model 256,
caption: A tandem inline-twin
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