On February 20, 1998, about 1115 eastern standard time, a Piper PA-28-140, N3965K, registered to an individual, operating as a 14 CFR Part 91 personal flight, experienced a loss of engine power during initial climb after takeoff from Twin Lakes Airport, Graniteville, South Carolina. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial damage, and the private-rated pilot was not injured. The flight originated about 4 minutes before the accident. The pilot stated that he was returning the airplane to his home field at Aiken Municipal Airport, South Carolina, having had maintenance performed on the gascolator, primer, and fuel selector by an A&P mechanic. Climbing through 400 feet agl, the engine began to run rough and lose power. The pilot felt his only option was a forced landing to a grass field. His final approach carried him further than his intended touchdown point, and he collided with an earth embankment and fence posts, shearing the landing gear, bending the propeller, both wing spars, and the engine mount. Subsequent teardown examination of the engine by FAA personnel revealed a broken exhaust valve in the number three cylinder. According to the FAA report, about 30 percent of the valve face was missing. The engine had undergone an annual inspection on June 6, 1997, and time since overhaul on the engine was reported as 1920.1 hours by the pilot.