On July 20, 2002, at 1330 central daylight time, a Meyer OTW-145, N34321, piloted by a private pilot, was substantially damaged when it landed in a wheat field approximately 5 miles south-southwest of Waupun, Wisconsin, following a total loss of engine power. The flight, consisting of a total of 6 OTW aircraft, originated at 1200 cdt from the Poplar Grove Airport (C77), Poplar Grove, Illinois, and was destined for the Wittman Regional Airport (OSH), Oshkosh, Wisconsin. The flight was being conducted under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. The pilot and pilot-rated passenger reported no injuries. The pilot reported that while in cruise flight en route to OSH, the engine suffered a complete loss of power. The pilot stated that manually actuating the fuel pump restored power for approximately 30 seconds. Unable to regain engine power, the pilot executed a forced landing into a wheat field. However, during the landing the airplane nosed over and came to a rest inverted. A post-accident investigation revealed no evidence of fuel in the fuel tanks. During the inspection, additional fuel introduced into the fuel tanks was noted leaking from the engine-driven fuel pump air vent. Examination of the fuel pump revealed a hole in the diaphragm.