Hirth 2704
The Hirth 2704 and 2706 are a family of in-line twin cylinder, two stroke, carburetted aircraft engines, with optional fuel injection, designed for use on ultralight aircraft and especially two seat ultralight trainers, single seat gyrocopters and small homebuilts. It was manufactured by Hirth of Germany. The series is out of production and were replaced by the Hirth 3202 and 3203 in May 2002. Development The 2706 was developed as a competitor to the Rotax 582 and is similar to the Rotax powerplant in being a two-cylinder in-line engine, with dual capacitor discharge ignition, although it is air-cooled, compared to the 582's liquid cooling. The 2704 was developed from the 2706 as a de-rated version to compete with the Rotax 503. Both the 2704 and 2706 use free air or fan cooling, with dual Bing 34mm slide carburetors or optionally fuel injection. The cylinder walls are electrochemically coated with Nikasil. Standard starting is recoil start with electric start as an option. The reduction drive system available is the G-50 gearbox, with reduction ratios of 2.16:1, 2.29:1, 2.59:1, 3.16:1, or 3.65:1. The engines run on a 50:1 pre-mix of unleaded 93 octane auto fuel and oil, or optionally 100:1 oil injection.