As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT STATED THAT WHILE IN FLIGHT AT 5000 FT, HE WAS UNABLE TO CHANGE THE MIXTURE SETTING ON THE LT ENGINE. THIS ENGINE HAD JUST RETURNED FROM A MAJOR O/H DUE TO TBO REQUIREMENTS. ACCORDING TO THE PILOT, THIS ENGINE HAD NOT HAD ANY PREVIOUS PROBLEMS IN THE PAST 1700 HRS OF FLIGHT. INSP FOUND THAT THE THREADS ON THE BARREL ASSY WERE WORN BEYOND LIMITS. BRONZE FILINGS WERE OBSERVED IN THE LT ENGINE COMPARTMENT BENEATH BARREL ASSY.