The Hirth 2702 and 2703 are a family of in-line twin cylinder, two stroke, carburetted aircraft engines designed for use on ultralight aircraft and especially two seat ultralight trainers, single seat gyrocopters, and small homebuilts.
The 2703 was developed as a competitor to the 50 hp (37 kW) Rotax 503 and is similar to the Rotax powerplant in being a two-cylinder in-line engine, with dual capacitor discharge ignition. The 2702 was developed from the 2703 as a de-rated version.
Both the 2702 and 2703 use free air or fan cooling, with Bing 34mm slide carburetors. The cylinder walls are electrochemically coated with Nikasil. Standard starting is recoil start. Reduction drive systems available are the G-50 gearbox with reduction ratios of 2.16:1, 2.29:1, 2.59:1, 3.16:1, or 3.65:1, or a multi-element cog belt drive. A tuned exhaust and electric start are optional.
The engines runs on a 50:1 pre-mix of unleaded 93 octane auto fuel and oil.
2702Twin-cylinder in-line, two stroke, aircraft engine with a single Bing 34mm slide carburetor. Produces 40 hp (30 kW) at 5500 rpm and has a factory rated TBO of 1200 hours. Still in production.
2703Twin-cylinder in-line, two stroke, aircraft engine with dual or optionally a single Bing 34mm slide carburetor. Produces 55 hp (41 kW) at 6200 rpm and has a factory rated TBO of 1000 hours. The 2703 has been largely supplanted in production by the
Hirth 3202, but in 2009 was still available as a special order from the factory.
2702Airfer TransanBrutsche Freedom 40FlightstarHy-Tek Hurricane 103ISON AirbikePreceptor N3 PupSpacek SD-1 Minisport2703Airfer TransanAirmotive EOS 001American Sportscopter Ultrasport 254CGS HawkExkluziv JokerFalconar Golden HawkKolb FirestarRemSchetMash RobustUS Light Aircraft HornetData from Recreational Power Engineering
Type: Twin cylinder, two-stroke, in-line, aircraft engineBore: 72 mm (2.8 in)Stroke: 64 mm (2.5 in)Displacement: 521 cc (31.8 cu in)Length: 413 mm (16.3 in)Width: 450 mm (17.7 in)Height: 376 mm (14.8 in)Dry weight: 70 lb (31.8 kg) with free air cooling, 76 lb (34.5 kg) with fan cooling, including recoil starter and exhaust. G-50 gearbox adds an additional 19 lb (8.6 kg)Fuel system: 1 X Bing 34mm slide type carburetorFuel type: unleaded 93 octane auto fuelOil system: 50:1 fuel/oil premixCooling system: free air or fanReduction gear: G-50 gearbox with reduction ratios of 2.16:1, 2.29:1, 2.59:1, 3.16:1, or 3.65:1, or a multi-element cog belt drivePower output: 40 hp (30 kW) at 5500 rpmCompression ratio: 9.5:1
