2si 500

2si 540 & 500
Type	Two-stroke aircraft engine
National origin	United States
Manufacturer	2si

The 2si 540 and 2si 500 are a family of in-line twin-cylinder, liquid-cooled, two-stroke, dual ignition, aircraft engines that were designed for ultralight aircraft.

The basic engine was originally designed and produced by JLO-Motorenwerke of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name. Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand. Cuyuna no longer markets engines for aircraft use although the 540 is still in production as a sport vehicle engine.

The 540 is a conventional twin-cylinder engine that weighs 90 lb (41 kg) in its L70 aircraft version. The engine features dual capacitor discharge ignition (single in the sport vehicle version), reed valve porting, tuned exhaust system, two slide venturi-type carburetors, liquid cooling, fuel pump, a cast iron cylinder liner, ball, needle and roller bearings throughout. The aircraft version was offered with an optional gearbox reduction system. Starting is electric starter or recoil starter.

The 500L85 is a special engine that was developed from the 540, by reducing the cylinder bore from 75 mm (2.953 in) to 72 mm (2.835 in). This was done to reduce the displacement to under 500 cc and allow the engine to be used for Formula 500 auto racing.

Data from Cliche & 2si

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