The pilot reported that the purpose of the flight was to test cooling plenum changes that he had recently made to the experimental amateur-built airplane’s automotive conversion engine. After takeoff on the planned flight in the airport traffic pattern, the pilot heard over the radio that another airplane was inbound to the airport for touch-and-go landings, so he flew away from the airport and performed ground reference maneuvers. Shortly after, the pilot returned to the traffic pattern, entering on the upwind leg. Upon turning onto the crosswind leg, his engine began to “sputter”, so he made a 180° turn to land on the opposite direction of the same runway. About that time, he noticed that the other airplane was back taxiing on the runway. He elected to not land on the parallel taxiway due to its condition and out of concern for a possible collision with another aircraft. The pilot overflew the other airplane on the runway, and shortly thereafter his airplane’s engine lost power completely as he neared the end of the runway. About that time the pilot was turning the airplane left, but could feel it slowing, so he leveled the wings and landed straight ahead, perpendicular to the runway. The airplane subsequently traveled over a grass embankment and contacted trees, resulting in substantial damage to the right wing and fuselage structure. The pilot stated that following the accident, an examination of the engine revealed that a bracket for the fuel/air mixture cable had “bent and overextended,” which resulted in the engine’s fuel/air mixture becoming excessively lean. The pilot stated that he had fabricated the bracket during a recent engine replacement and knew that a new bracket would need to be refabricated but had not completed the task it before the accident flight. Based on this information, it is likely that the loss of engine power was the result of the improperly fabricated bracket, which resulted in an excessively lean mixture to the airplane’s engine.