On August 28, 1993, at 0745 central daylight time, a Beech 19A, N6130N, registered to Flying Muskateers of Troy, Missouri, and operated by a student pilot, experienced a rejected takeoff on runway 8 (2,200' wet/turf) at Troy, Missouri. The airplane sustained substantial damage when it exited the end of the runway, impacted a fence, and crossed a gravel road. The student pilot reported no injuries. The solo instructional 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The local flight was originating at the time of the accident. The pilot originally told the FAA inspector that on takeoff he became concerned that the airplane was not accelerating well and elected to abort the takeoff. He stated that the dew of the turf resulted in poor braking action and the airplane overran the departure end of the runway, and impacted a fence and terrain off the end of the runway. He also stated that he was concerned about the possibility of fuel contamination. Additional attempts to contact the pilot or to get him to make a written statement concerning circumstances surrounding the accident were not successful. He did not answer repeated attempts to contact him by mail or by telephone. During an inspection of the airplane yellow colored fuel was found in the left tank. Blue/green color fuel was found in the right tank. Yellow fuel was found in the gascolator. Subsequent to the discovery of the fuel, the engine was run. While operating at full power on the left tank (yellow fuel), the engine lost RPM, ran rough and produced black smoke out of the exhaust. When the fuel selector was switched to the right tank and run on the other fuel (blue/green), the engine operated at rated RPM with no noted discrepancy. An evaporation test was made between the fuel from the left tank of the accident airplane, kerosene, and 86 octane rated motor fuel gasoline. There appeared to be no appreciable difference in observed evaporation rate between the fuel from the accident airplane and the 86 octane motor fuel, while the kerosene left an oily film. While no specific determination was made as to the nature of the yellow fuel found, the accident airplane had no Supplemental Type Certificate for use of any fuel in lieu of AV-gas.