The pilot reported that he performed a fly-by at a restricted landing area and when he applied power the engine did not respond. He attempted a 180 degree turn to land on the runway in the opposite direction, but the right wing tip struck the ground prior to the completion of the turn. Post accident examination of the airplane revealed that a clamp attached to the engine mount that secured the throttle cable to the engine mount structure had rotated. This prevented the opening of the carburetor butterfly when the throttle was advanced. Additional information obtained during the investigation revealed that the pilot's most recent application for a medical certificate was denied on November 14, 2003. Federal Aviation Administration regulations state that a person operating an airplane as a light sport aircraft must have been found eligible for the issuance of at least a third-class airman medical certificate at the time of his or her most recent application if that person has applied for a medical certificate in the past. In addition, the accident airplane, an Ercoupe 415D, which has a maximum gross weight of 1,400 pounds, does not comply with the 1,320 pound maximum gross weight limitation prescribed in the regulations.