As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT NOTICED LACK OF POWER AND ROUGHNESS AFTER TAKEOFF. RETURNED TO FIELD, DISCOVERED INOPERATIVE RT MAGNETO. DISASSEMBLY OF RT MAGNETO REVEALED ROTOR SHAFT HAD SHEARED FLUSH WITH BOTTOM OF CAM CUTOUT. THE REMAINING ROTOR AND DISTRIBUTOR BOTH ROTATED FREELY. NO EVIDENCE OF PROBLEMS WITH EITHER GEAR. PROBABLE CAUSE IS A DEFECT IN MFG (POSSIBLY BAD METAL OR STRESS CRACK FROM MACHINING CAM SLOT. (K)