The Hirth F-33 is a single cylinder, two stroke, carburetted aircraft engine designed for use on ultralight aircraft, including powered paragliders and ultralight trikes. the engine is noted for its extremely light base weight of 350NaN0. It is manufactured by Hirth of Germany.[1] [2] [3]
The F-33 was intended to fill the niche previously occupied by the now out-of-production 280NaN0 Rotax 277. The F-33 uses free air cooling, dual capacitor discharge ignition and reed valve induction, with a single Bing 34mm slide or optional diaphragm type carburetor. The cylinder walls are electrochemically coated with Nikasil. Standard starting is recoil start. A belt reduction drive system, fuel injection, tuned exhaust and electric start are optional.
The engine runs on a 50:1 pre-mix of unleaded 93 octane auto fuel and oil. Recommended time between overhauls is 1000 hours.
The F-33 produces 220NaN0 at 5200 rpm and 280NaN0 at 6500 rpm.