What was found
DURING MAG CHECK, AT PREFLIGHT RUN UP. FOUND CONTACTS INTERMITTENT WHEN TIMING LIGHT USED TO CONFIRM TIMING, REMOVED AND OPENED MAG FOR INSPECTION. FOUND BEARING CAP ASSY LOOSE IN CASE WHICH ALSO LED TO ROTOR SHAFT EXHIBITING EXCESSIVE PLAY AND END CLEARANCE. THE INTERNALS OF THE MAGNETO WERE COATED WITH FINE DUST, BELIEVED TO BE ALUMINIUM POWDER. THE BEARING CAP DOUBLES AS THE MOUNTING FOR THE CONTACTS SO THE LOOSE CONDITION LEAD TO ERRATIC CONTACT OPERATION AND LIKELY VARIABLE MAGNETO TIMING WHILE ENGINE RUNNING.