On March 9, 1997, about 2012 eastern standard time, a Cessna 175, N9485B, was substantially damaged when it impacted the terrain during a forced landing from cruise flight near Weirs Cave, Virginia. The certificated private pilot and passenger were not injured. Night visual meteorological conditions prevailed and no flight plan was filed for the personal cross country flight conducted under 14 CFR Part 91. The flight originated from Morristown Municipal Airport, Morristown, New Jersey, about 1645. The pilot reported that he was in cruise flight at 6,500 feet and 20 miles from his destination when the engine began to run rough. The pilot suspected carburetor icing, applied carburetor heat, and the "situation remedied itself." According to the pilot, "the situation repeated itself," so, he again applied carburetor heat and descended to 4,500 feet. At 4,500 feet, the engine stopped completely, and the pilot set up for a forced landing. The pilot reported that the right fuel gauge needle indicated approximately a quarter tank, and the left fuel gauge needle indicated "a little over empty, but was not functioning." The pilot stated that "he had no reason to believe that the fuel was exhausted because I had topped off at Morristown." The airplane impacted the terrain in a partially wooded field about 3 miles north of Shenandoah Valley Regional Airport. A Federal Aviation Administration (FAA) Inspector examined the wreckage. The FAA Inspector reported that there was less than 2 cups of fuel in the main fuel line, a third of a cup in the carburetor, with the gascolator about half full. According to the Inspector, "the ground immediately in the vicinity of where the fuel line to the carburetor was broken, showed a 3 to 6 inch fuel stain which was not wet in the vicinity of the broken line." The Inspector continued, "there were no signs of fuel stains to indicate that fuel was leaking from the fuel tanks, or from elsewhere." The Cessna owner's manual stated that the airplane's total fuel capacity was 52 gallons, with 43 gallons useable. The cruise performance chart in the owner's manual indicated that the cruise performance with rich mixture at 5,000 feet altitude and 72% power would yield 12.3 gallons of fuel per hour, with and endurance time of 3.5 hours. The pilot had 8 total hours in make and model prior to this cross country flight. He reported refueling the airplane with 43.1 gallons at Morristown Municipal Airport, prior to his return flight to Shenandoah Valley Airport. When questioned by the FAA Inspector on the airplane's fuel system, the pilot stated that the fuel available for flight planning was 52 gallons. The FAA Inspector commented that the pilot's description of how he leaned the fuel was vague, and that "the pilot's knowledge of the aircraft and its systems was very weak."