On June 23, 1995, at 1750 eastern daylight time, a Kemp Acro-Sport II, N27727, was destroyed after it impacted the ground during a forced landing at Honeoye Falls Airport, Honeoye Falls, New York. The private pilot, the sole occupant, received minor injuries. No flight plan had been filed and visual meteorological conditions prevailed at the time. The flight was conducted under 14 CFR Part 91. The Federal Aviation Administration (FAA) Inspector reported that the pilot/airplane owner purchased and reassembled the aircraft which had been hangared for 5 years. The pilot stated that during reassembly of the airplane he did not drain the carburetor bowl, or flush the fuel tank. He stated that the airplane had flown about 3 to 4 hours since it was reassembled. The pilot stated that on the flight prior to the accident flight, the engine lost power during traffic pattern operations. A successful emergency landing was made in a field, approximately 3/4 of a mile from the airport. The pilot reported that he got a car ride back to the airport, gathered some tools, and returned to the airplane to check the engine. He stated that he found no mechanical problems; however, when he drained the sump, he found water and other unknown contaminants. The pilot reported that he drained fuel until he did not see any contaminants, then decided to fly the airplane back to the airport. He indicated that when the airplane was reentering the airport traffic pattern, the engine lost power again. The pilot attempted to make an emergency landing on the runway, but the airplane impacted the ground approximately 100 feet short of the runway. During postaccident examination of the wreckage, the FAA Inspector found fuel in the system that measured approximately one third of the system's capacity. Unknown particles/contaminants were detected in the fuel samples drained from the tank and the carburetor bowl. Closer examination revealed black particles approximately 1/16th to 1/8th of an inch found in the samples. The source of these particles was unknown.