On August 25, 2006, at 1330 Pacific daylight time, a Boeing E 75 (Stearman), N58980, came to rest inverted following a forced landing in a field in Morgan Hill, California. The pilot was operating the privately registered airplane under the provisions of 14 Code of Federal Regulations Part 91. The commercial pilot sustained minor injuries, and one passenger (the owner of the airplane) was not injured. The airplane sustained substantial damage. Visual meteorological conditions prevailed and no flight plan was filed for the local area flight. The pilot departed from Reid-Hillview Airport, San Jose, California, at 1300. According to the owner of the airplane, the purpose of the flight was to perform aerobatics in the local area. During one of the maneuvers, flames emanated from the right side of the engine. The pilot pulled the mixture to the lean position and the fire went out. A restart was attempted but was unsuccessful so the pilot performed a precautionary landing to a field. The airplane pitched forward just prior to touchdown and nosed-over. The aircraft recovery personnel noted that when the airplane was righted from its inverted position, fuel poured from the carburetor area. They turned the fuel selector to the OFF position, placed the mixture control to idle cutoff, drained the remaining fuel from the tanks, and removed the wings for transport. On November 17, 2006, a National Transportation Safety Board investigator examined the wreckage. The investigator turned the fuel selector to the ON position and placed the mixture control to full rich. Residual fuel from the airplane's fuel lines could be heard filling the carburetor bowl. Fuel was then observed leaking at a rapid rate from the carburetor area. The mixture control was placed in the idle cutoff position and fuel still leaked from the carburetor area. The fuel selector was then placed in the OFF position and fuel stopped flowing from the carburetor. The carburetor, a Bendix Stromberg NAR6D, was removed from the engine and the investigator noted that the intake manifold displayed heavy black soot throughout. The throttle inlet and venturi was blackened with heavy soot. The carburetor halves were split to examine the float. The metallic float did not display any cracks or holes that would permit the float to sink. Fuel was added to the bowl and the float floated to a level that completely shut off the fuel inlet line. No anomalies were noted with the carburetor after its removal, with the exception of a leather seal that protected the accelerator pump plunger housing was torn. Thumb compression was obtained on each cylinder, with all of them producing compression. Dark soot was noted throughout the intake and exhaust systems.