On May 9, 2004, at 1555 central daylight time, a Piper PA-12, N2368M, piloted by a commercial pilot, sustained substantial damage during a forced landing near Hartford, Wisconsin. The airplane was on initial climb from runway 18 (2,000 feet by 200 feet, dry grass) at the Hartford Municipal Airport (HXF) when it experienced a loss of engine power. Visual meteorological conditions prevailed at the time of the accident. The personal flight was operating under the provisions of 14 CFR Part 91 without a flight plan. The pilot and his passenger were not injured. The local flight was originating at the time of the accident. According to the pilot's written statement, there were no anomalies with the operation of either magneto and there was no indication of carburetor ice accumulation during the pretakeoff engine tests. The pilot reported that he experienced an uneventful takeoff roll and climb out until approximately 350 feet above ground level, at which time the engine lost power. The pilot, who was seated in the rear seat, instructed the pilot-rated passenger to switch fuel tanks, check the position of the magneto switch, and to select carburetor heat on. The pilot stated there was no change in the engine operation and he performed a forced landing into an open field. The main landing gear collapsed when it encountered the soft terrain condition. Subsequent to the accident, two gallons of fuel were recovered from the fuel system and the samples did not contain water or particulate contamination. The damaged propeller was replaced with a serviceable propeller so that an engine operational test could be accomplished. The engine started and idled between 550 and 600 rpm. The engine was then accelerated to 3,350 rpm and no anomalies were noted during the test. The temperature and dew point were plotted on a carburetor icing probability chart, originally published by Transport Canada. The conditions at the time of the accident were conducive for moderate icing at cruise power and serious icing at descent power.