| A number of ultralight aircraft manufacturers have started to build part 103 legal ultralight again. With all the attention that the light sport category has gotten little if any changes have taken place with respect to increasing weights for ultralights. So other ways have had to be found to build a legal part 103 ultralight. Recreational Power the U.S. Hirth Aircraft engine distributor has been working with the factory, and has put their twin cylinder opposed F-23 engine, which has been on the market for over 20 years on a weight reduction program. Hirth has redesigned the engine with a lighter crankshaft, and reduction drive, switched to a pull starter with a decompression system, which has reduced the weight for a 50 HP engine to 71 lbs. (Note the older version of the engine is still available, the newer engine has a UL designation.) This is 5 lbs heavier than a single cylinder 277 Rotax which put out only 28 HP. The decompression system works automatically on start up via a compression bi-pass system. The engine comes standard with dual carbs, dual ignition, and a 20 amp charging system. It has a 1 year total warranty and a 3 year pro rated warranty. Top end TBO is 500 hours with engine rebuild at 1,000 hours. Raven Trikes will be one of the first manufacturers to use the engine on the part 103 legal trikes. | 
