As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ENGINE RUN-UP PRIOR TO FLIGHT WAS NORMAL. IN CLIMBOUT, LT ENGINE BEGAN SURGING. PILOT RETURNED TO BASE. ENGINE RUN-UP CARRIED OUT BY AMO INITIALLY SHOWED NORMAL. FURTHER TESTING AT HIGH POWER SHOWED SURGING. PROBLEM TRACED TO MAGNETO.