On October 7, 2012, about 1430 central daylight time, a Challenger II CW Experimental, N530MW, owned and operated by the pilot, sustained minor damage during a forced landing near Sandwich, Illinois. The certificated private pilot was not injured. The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91, with no flight plan filed. Visual meteorological conditions prevailed. According to pilot testimony, the airplane experienced a total loss of engine power after initial takeoff from Woodlake Landing Airport (IS65). The pilot conducted a forced landing into a cornfield off the departure end of the runway. The airplane was equipped with a Rotax 503 engine, serial number M5555721. This 2-stroke, 2-cylinder in-line engine is utilized with experimental, uncertificated aircraft and is no longer in production. Examination of the engine revealed a failure of the power takeoff lower rod bearing due to corrosion. Debris from the lower rod bearing transferred through the transfer port to the top of the piston, damaging the piston and head. In addition, oil leaks around the cylinder head gasket were observed, as well as corrosion on two of the four cylinder head bolts, with one cylinder head bolt absent. The engine was operated infrequently, accumulating a total of 163 hours over a nine year period. The owner had recently purchased the airplane and operated the engine for approximately four hours. The Rotax operations manual directs short and long term engine preservation instructions and the maintenance schedule directs an engine overhaul at 300 hours or five years, whichever comes first. According to the mechanic who performed the examination, the engine overhaul and preservation instructions were not accomplished.