What was found
AFTER INSTALLATION OF FACTORY REBUILT ENGINE. PERFORMED GROUND RUN OF ACFT, AT ALL SETTINGS THE ENGINE RAN TOO RICH, AND ADJUSTMENTS HAD NO EFFECT. ACFT WAS NOT AIRWORTHY. REMOVED FUEL SERVO FROM ENGINE, SENT OUT FOR REPAIR. REINSTALLED FUEL SERVO AFTER REPAIR, AND ENGINE PERFORMED SATISFACTORY, RETURNED ACFT TO SERVICE.