On September 17, 2004, at about 1800 central daylight time, a Cessna 150L single-engine airplane, N11418, was substantially damaged during a forced landing following a loss of engine power while in cruise flight near Mountain Home, Texas. The private pilot and his passenger were not injured. The airplane was registered to a private corporation and operated by Kerrville Aviation of Kerrville, Texas. Visual meteorological conditions prevailed for the Title 14 Code of Federal Regulations Part 91 cross-country flight for which a flight plan was not filed. The round-robin flight originated from the Kerrville Municipal Airport (ERV), Kerrville, Texas, approximately 2 hours and 45 minutes prior to the accident with a stop at Lampasas Airport (T28), Lampasas, Texas, to pick up a passenger. According to the 375-hour private pilot, before leaving Kerrville Municipal Airport, he asked the line crew to "top-off" the fuel tanks. The line crew indicated they had filled both tanks, but the pilot reported that because he did not have a ladder available, he did not visually check the fuel level before departure. On the return flight from Lampasas Airport, the pilot reported that while near Mountain Home, Texas, at approximately 2,800 feet above ground level, the engine briefly ran rough and then lost power. The pilot observed that the fuel gages were "one needles width above empty", and attempted to restart the engine. When the engine failed to start, the pilot elected to land in a freshly planted field. The pilot reported that the touch down and initial landing roll were uneventful, but the nose gear subsequently collapsed and the airplane nosed over coming to rest inverted. A representative from the Federal Aviation Administration responded to the accident site and reported that he could not see or hear any fuel in the left tank and that the right tank contained approximately one gallon of fuel. He further reported that the left wing outboard leading edge was crushed aftward and that both wing rear spars were buckled. An NTSB investigator performed a post accident examination of the engine and fuel system. The lower engine mount was supported and a temporary fuel tank was installed to facilitate operating the engine while still on the airframe. The engine was then started and was run for approximately 30 minutes. The left and right magneto checks indicated an approximately 75 rpm drop and the oil pressure and oil temperature remained in the normal operating range. The fuel gascolator screen and carburetor inlet screen were both found to be clean. The post engine run compressions where found to be as follows: #1 76/80, #2 76/80, #3 74/80, #4 70/80. The left fuel tank vent was found obstructed. The crossover vent and single vented fuel cap were unobstructed and performed normaly.