As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE BECAME HARD TO START. ON INVESTIGATION, FOUND TIMING HAD SLIPPED ON THE IMPULSE MAG. CHECKING INTERNAL TIMING, IT WAS DETERMINED THAT THE POINTS HAD CLOSED TO THE POINT THE SPARK OUTPUT WAS DEGRADED EVEN THOUGH THE PREFLIGHT MAG CHECK WAS WITHIN LIMITS.