On March 8, 1998, at 1617 hours Pacific standard time, a Cessna 182, N5704B, nosed over in soft soil during a runway overrun following a loss of power in the initial takeoff climb at the Santa Rosa, California, airport. The aircraft sustained substantial damage and the pilot and his passenger, the sole occupants, were not injured. Visual meteorological conditions prevailed for the personal flight and no flight plan was filed. The local flight was originating at the time of the accident. The pilot reported that prior to conducting the preflight, he washed the plane and sumped the fuel from both wings and the carburetor drain several times. After completing the preflight, he sumped the fuel again. The pilot stated that just after takeoff, about 50 feet agl, the engine backfired twice. He called the tower and told them that he was aborting the takeoff, then pulled the power back. He landed and applied the brakes, but was already close to the end of the runway. The pilot then steered the aircraft to the right toward a large, open field. The grass was soft due to recent rains and the nose wheel dug into the terrain. The plane nosed over causing substantial damage to the wing spars. A Federal Aviation Administration (FAA) certified airframe and powerplant mechanic conducted an inspection of the engine on April 13, 1998. He reported that there was mechanical continuity established from the propeller to the accessory section and the valve assemblies. Thumb compression was verified in all four cylinders. The accessory drives were inspected and determined to be functioning, including the generator, magnetos, and the prop governor. The magnetos were inspected for overall integrity, drive couplings, points, and timing. The magnetos were both fully functional, with proper point gap and timing, and showed no carbon trails or other evidence of arcing. The magneto switch was tested for intermittent operation and was found to be in good condition. The magneto harness was also in good condition. The spark plugs showed normal color, wear patterns, and electrode gaps according to the Champion Check-a-Plug Chart. All the spark plug leads sparked in proper sequence with hand rotation of the propeller. The carburetor and induction system was clear and unobstructed. The float chamber of the carburetor was drained and it was noted that there was a small amount of fuel present. There was no evidence of contamination such as water or particulate present in the float bowl. Continuity was established in the throttle arm and the mixture controls. Approximately 25 gallons of fuel were drained from the wing tanks. The mechanic reported that the fuel was blue in color and the odor was consistent with 100LL aviation fuel. He did not observe any visible contamination. The fuel lines to the gascolator and the gascolator itself were intact. A small amount of fuel was present in the gascolator with no evidence of contamination. There were no mechanical discrepancies noted.