On May 28, 2003, about 1255 Pacific daylight time, an experimental Callahan Murphy Rebel airplane, N6324H, lost engine power during cruise flight and collided with terrain near the southeast end of Clearlake, California. The pilot/owner operated the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, sustained minor injuries; the airplane sustained substantial damage. The personal cross-country flight departed Roseburg Regional Airport, Roseburg, Oregon, about 0900, and was en route to Gnoss Field Airport, Novato, California. Visual meteorological conditions prevailed, and a visual flight rules (VFR) flight plan had been filed. In a written statement, the pilot reported about 1230, while in cruise flight at 7,500 feet msl, the engine started to run rough. He applied full rich mixture, and pumped the throttle. This alleviated the problem for a while, but then the engine lost total power. He slowed the airplane to 65 knots, and advised controllers on the emergency frequency, 121.5, of an engine problem, along with position information. The pilot decided to make a forced landing in a clearing on the southeast side of Clearlake. However, about one mile out he saw a low ridge that the airplane would have to clear before he would be able to land in the clearing. When it became apparent that he would not be able to clear the ridge, he applied full flaperons and raised the nose of the airplane in order to contact the ground "somewhat parallel to the slope and at a minimum controllable airspeed." The airplane incurred damage to the main landing gear, firewall, propeller, and fuselage skin. After exiting the airplane, the pilot found that the right fuel valve was closed. During the pilot's preflight procedure, he normally turns both fuel valves ON to check the fuel drains, and leaves the valves ON until he lands. The pilot further commented that he did not recall any distractions during the preflight, and remembers checking both belly drains. The pilot stated that he left Roseburg assuming that both valves were open. A Federal Aviation Administration inspector examined the airplane after the accident. He stated that the right fuel tank was about 80 percent full of fuel, and the left fuel tank was less than 10 percent full of fuel. The pilot stated that the accident could have been prevented by the use of checklists. He reported no pre-impact mechanical malfunctions or failures with the airplane.