On May 17, 1998, at 1900 central daylight time, a Pitts S-2A, N31517, was substantially damaged when the engine lost power during takeoff. The airplane was turning back to the airport when it crashed in a wheat field about 1/4 mile south of the Benton Airport, Benton, Kansas. The pilot received serious injuries. The CFR 14 Part 91 flight departed the Benton Airport on a local maintenance flight. Visual meteorological conditions prevailed and no flight plan had been filed. The pilot reported that the engine had just been installed in the airplane after it had been overhauled. The purpose of the flight was a maintenance check flight and engine break-in. The pilot reported that he conducted the normal preflight and engine run-up procedures in accordance with the Airplane Flight Manual. He reported no abnormal indications were observed. The pilot reported that the takeoff and initial climbout were normal with no anomalies observed. He reported that at approximately 400 feet agl, the engine sputtered and lost partial power. He established a nose down attitude to maintain airspeed. He turned to the left. He reported the engine lost complete power and he conducted a forced landing to a wheat field adjacent to the airport. A witness to the accident, who had also helped the pilot install the overhauled engine in the airplane, reported that the airplane seemed to be developing full power and accelerating normally. He reported that the airplane climbed to 400 feet and turned right when the engine popped and sputtered. He reported the engine went to about half power. The airplane started a turn to the left and during the turn the engine quit. He reported the nose pitched down about 45 degrees. He reported, "The airplane continued on this -45 degree line, wings level and in control until impact." The witness reported that during the power-on portion of the flight, no smoke or vapor trails were seen. The witness reported the propeller continued to windmill after the engine quit. An Airworthiness Inspector from the Federal Aviation Administration inspected the airplane at the accident site. He reported that no mechanical anomalies to the airframe or engine were noted during the inspection. On onsite inspection of the engine revealed that the engine had incurred very little impact damage. The engine was sent to engine manufacturer and an engine run was accomplished. The engine ran when it was put on the test stand.