As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ROUTINE 500 HOUR INSPECTION OF MAGNETO, THE IMPULSE COUPLING WAS FOUND TO BE CRACKED. CRACKS ORIGINATE FROM SHARP CORNERED FEATURE OF IMPULSE COUPLING FLYWEIGHT BASE PLATE. THIS CORNER FORMS THE FULL ADVANCE STOP OF THE IMPULSE COUPLING. CRACK DISCOVERED USING "MAGNETIC PARTICLE INSPECTION" NDT METHOD. HAVE SEEN A LARGE PERCENTAGE OF IMPULSE COUPLINGS USED ON THE PN 6310, SLICK MAGNETO DEVELOPE THIS SAME DEFECT. HAVE ALSO SEEN IT ON OTHER ENGINES WITH THIS SAME MODEL MAGNETO INSTALLED.