At 10:30 mountain time, a Piper PA-18-150 lost power on takeoff and struck the perimeter fence at El Tiro Gliderport. The pilot was not injured. The pilot said he was making a flight prior to towing gliders to make sure that the airplane was working properly. He conducted a preflight and saw the fuel selector pointing toward the left. The pilot said he had been flying a Cessna 120 that has a similar looking fuel selector but operates opposite the Super Cub. In the 120, the left position is fuel on, in the Cub its fuel off. The engine sputtered on takeoff and the pilot tried to slip the airplane back to the runway, but the engine momentarily caught again and pushed him into the fence.