Narrative
The pilot reported experiencing a problem with spark plugs loading up before departing Sacramento, California, on a cross-country flight. The magneto had been overhauled prior to departure. The pilot stated that the engine ran well except for a brief period of spark plug loading on one cylinder, which was cleared by leaning the mixture. En route stops were made at Tehachapi, California, and Flagstaff, Arizona, for fuel.
During takeoff at Flagstaff, the pilot reported that the engine lost power at approximately 100 feet above ground level. However, witnesses reported that the engine was missing (misfiring) during the takeoff roll. One witness, a certified flight instructor, stated that from where he first heard the engine, it was missing steadily, but the aircraft continued on the takeoff and rolled approximately another 1,500 feet before the pilot took off with the engine still missing. After taking off, the aircraft settled, hit treetops, and crashed.
Findings
The airport elevation was 7,012 feet. Examination of the engine revealed that the right magneto was found at 3 degrees before top dead center (BTDC). However, there were scrape marks where it had rotated; the retaining nuts were snug but not tight. The left magneto was in its proper position to fire at 25 degrees BTDC.
No additional information regarding the aircraft, occupants, or injuries was provided in the source.