On May 13, 2003, about 1900 central daylight time, a Piper J3C-65, N70971, piloted by a commercial pilot, sustained substantial damage when it struck a fence and nosed over during a forced landing. The airplane experienced a loss of engine power while performing a go-around at the Westosha Airport, Wilmont, Wisconsin. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The pilot was not injured. The flight originated from the Palwaukee Municipal Airport, Wheeling, Illinois about 1835. The pilot reported that he performed a go-around and initially, the engine responded normally. He said that after gaining about 150 feet of altitude, the engine started to sputter and the rpm's dropped. He said that he was unable to maintain altitude and selected a field in which to perform a forced landing. When the airplane was about 75 feet above ground level, engine power returned and the pilot elected to attempt to return to the airport. The pilot reported that he was able to climb for about 10 to 20 seconds before the engine rpm again dropped. The pilot executed a forced landing, during which the airplane impacted a barbed wire fence and nosed over. The pilot reported that he departed PWK with 5 gallons of fuel on board. The total fuel capacity of the airplane is 12 gallons. No pre-impact anomalies were found during a postaccident examination of the airplane by a Federal Aviation Administration Inspector. No fuel was recovered from the aircraft fuel tank, however, evidence of fuel staining was found on the ground beneath the fuel tank. A weather reporting station about 11 nautical miles northwest of the accident site recorded the temperature and dewpoint as 16 degrees Celsius, and 2 degrees Celsius respectively.