On July 20, 2022, about 0815 mountain daylight time, a Maule M-5-235C, N6224M, sustained substantial damage when it was involved in an accident in Three Forks, Montana. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, who held a mechanic certificate with airframe and powerplant ratings with inspection authorization, the accident flight was the first flight following an engine and magneto overhaul, in addition to the installation of new avionics. He reported his completion of several engine test runs and multiple full-power, high-speed test runs. Confident of the engine’s performance, the pilot departed on the local flight and continued with engine break-in procedures. He conducted several flight maneuvers and the engine operated normally. With the intent to land, he was established in the right traffic downwind leg of the airport traffic pattern when he noticed that the engine rpm was winding down slowly. He attempted to troubleshoot the anomaly without success. He pitched for best glide with no flaps applied and made a right 180° turn for runway 03. However, the airplane’s sink rate was too high to land on the runway. The airplane touched down about 1,000 ft short of the runway threshold on an unplowed pasture and collided with a barbed wire fence. The airplane sustained substantial damage to its longerons near the wing’s attach points, the left-wing spar, and lift struts. The postaccident examination of the engine’s single-drive dual magneto revealed that the right magneto capacitor wire was attached utilizing an automotive-style terminal, that was bent 90°, rather than a right-angle flag terminal. Further examination revealed that the wire had separated within the crimped section of the terminal. The left magneto P-lead was deteriorated, and had an area of exposed wire that resulted in a ground fault when the P-lead was tested with a multimeter. The pilot reported that he could have avoided the accident if he had immediately turned toward the runway when the engine began losing power, rather than continuing the downwind leg while troubleshooting.