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2si 500 / 540
Cuyuna 500 / 540

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 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 was 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.


Gasoline sport vehicle engine for Formula 500 auto racing. Dual carburetors, 83 hp (62 kW) at 8000 rpm.

Gasoline aircraft engine, dual carburetors, 70 hp (52 kW) at 7000 rpm, weight 90 lb (41 kg), out of production.

Gasoline sport vehicle engine for auto racing, kart and all-terrain vehicle applications. Dual carburetors, 89 hp (66 kW) at 8000 rpm.



Type: Twin-cylinder, two-stroke aircraft engine
Bore: 75 mm (2.95 in)
Stroke: 61 mm (2.40 in)
Displacement: 540 cc (32.95 cu in)
Length: 17.5 in (444.50 mm)
Width: 14.0 in (355.60 mm)
Height: 15.0 in (381.00 mm)
Dry weight: 90 lb (41 kg)
Valvetrain: reed valve porting
Ignition: Electronic
Fuel type: Minimum 92 octane
Oil system: premixed oil and fuel
Cooling system: liquid cooled
Reduction gear: optional gearbox
Reduction: Mechanical Integral damper
Reduction Ratio: 1.66-1 to 3.00-1
Power output: 70 hp (52 kW) at 7000 rpm
Max torque: 71 at 7000 rpm
Price 1998: 29,950 Fttc





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