As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE DEVELOPED A SHUDDER EVENT ON CLIMB OUT. MOMENTARY DROP IN POWER AND RPM. RETURNED TO KOSU WITH OUT ANY OTHER ISSUES. ALL STICKING VALVES HAVE BEEN CYLINDERS #2, AND/OR #4. TECHS COMPLIED WITH LYCOMING SB N0.388C REAMED EXHAUST VALVE GUIDES. THIS CORRECTED THE ENGINE SHUDDER ISSUE.