On October 2, 1999, approximately 0750 mountain daylight time, a Piper PA-12, N2493M, registered to and operated by the pilot, was substantially damaged when it veered off the side of the runway while landing at Las Cruces International Airport, Las Cruces, New Mexico. The private pilot and his private pilot certificated passenger were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated at El Paso, Texas, approximately 0730. The pilot said that while on final approach to runway 26, he noticed that engine power remained too high even though the throttle had been retarded completely. He made a go around. On the second approach to the same runway, he noticed engine power was still too high with the throttle closed. He initiated a second go around and when the airplane was 50 feet above the ground, he slowly moved the mixture control towards idle cutoff "to decrease power." The airplane touched down at high speed and, according to the pilot, directional control was lost when he became distracted, and the airplane ground looped to the right. The left wing buckled when it struck the runway, and the side loads tore off the left main landing gear and damaged the right main landing gear. The pilot later reported the clamp that secures the throttle sleeve to the throttle housing had come loose, allowing the sleeve (not the cable) to move when the throttle control was operated.