On July 20, 1996, at 0920 hours mountain standard time, an experimental Graham Falcon XP, N647AA, collided with terrain after an in-flight loss of control after takeoff from Falcon Field, Mesa, Arizona. The airplane was substantially damaged and the certificated private pilot was not injured. The airplane was being operated by the pilot/owner as a personal flight. The local flight originated from Falcon Field at 0915. Visual meteorological conditions prevailed at the time. The pilot remained in the traffic pattern after takeoff and initiated a go-around during the first landing. During the climb, the engine lost power and decelerated to idle. The pilot reported to the Falcon Field air traffic control tower he was having engine problems and asked to return to the airport. As the pilot turned the airplane to return to the airport, the engine lost all power. The airplane subsequently landed in an orange grove about .5 miles northwest of the airport. The engine was examined by the Federal Aviation Administration (FAA) with the assistance of a mechanic familiar with Rotax engines. There was no evidence of mechanical failure or malfunction found with the engine or any of the engine components. Examination of the airplane's fuel system revealed the tank vent in the fuel cap was closed. According to the mechanic, the design of the cap consisted of a rubber stopper that was squeezed by a threaded wing bolt. A small hole in the stopper served as a vent. When the squeezing pressure was applied to the rubber stopper by turning the wing nut, the wall would expand decreasing the diameter of the vent hole. He indicated that excessive tightening of the wing nut would also squeeze the vent closed. According to the FAA, the pilot should have determined the airplane's fuel quantity and secured the fuel cap during his preflight check. The pilot indicated in his accident report his total flight experience was 82 hours, of which 4 were in the Graham Falcon XP.