On October 27, 2002, at 1010 eastern standard time, a Cessna 152, N49422, was substantially damaged during a forced landing, following a loss of power, in Springfield, Ohio. The certificated private pilot was seriously injured, and visual meteorological conditions prevailed at the time. No flight plan was filed for the flight, between Moraine Airpark (I73), Dayton, Ohio, and Port Bucyrus-Crawford County Airport (17G), Bucyrus, Ohio. The personal flight was conducted under 14 CFR Part 91. According to the pilot, the airplane had just undergone a 100-hour inspection during which the number 3 cylinder was replaced. He performed a preflight inspection prior to his departure and observed no anomalies with the airplane. While en route to Bucyrus, the airplane was at an altitude of 2,000 feet, in the vicinity of Springfield, Ohio, when the pilot noticed that a small amount of pressure was required on the yoke to maintain level flight. The pilot believed he was experiencing a partial loss of power, and applied carburetor heat and enriched the mixture. The pilot was still unable to maintain level flight. The pilot decided to make a precautionary landing at the Springfield-Beckley Municipal Airport (SGH), Springfield, Ohio, and was cleared to land. About 4 miles northeast of the airport, he realized he would not be able to make it to the runway, and prepared for a forced landing to a football field. The airplane touched down on the 27 yard line, the landing gear sheared off, and the airplane came to rest on the 2 yard line. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed substantial damage to both wings, and the fuselage and empennage sections. Examination of the engine by the FAA inspector revealed the number 3 cylinder exhaust rocker arm set screw had backed out and the jam nut was observed lying in the rocker cover. Additionally, the "1102" plug was missing from the intake port of the number three cylinder. A measurement was taken of the tappet clearance (between the rocker foot and the valve stem tip) and noted to be .300 inch. According to published Lycoming Service Instructions, the tappet clearance should have been .006 to .012 inch. Examination of the engine logbook revealed an entry for a 100-hour inspection, dated October 26, 2002. The entry stated, "...Replaced #3 cylinder with serviceable unit using new rings and gaskets. Ground run and check for ops and leaks. All OK..." The mechanic who performed the inspection stated that the cylinder was replaced due to an exhaust valve leak.