What was found
INSTALLED O/H HA-6 CARBURETOR, ON GROUND RUNS NOTED ENGINE EXTREMLY ROUGH AT POWER SETTING ABOVE 1400 RPM, STRONG ODOR OF FUEL AND BLACK SMOKE FROM EXHAUST. USE OF MIXTURE CONTROL AT 1400 RPM GAVE 200 RPM RISE AND CLEARED CONDITION. UNABLE TO REACH TAKEOFF RPM AT 41" MANIFOLD PRESSURE WITHOUT LEANING AT FIELD ELEVATION OF APPROX 700 FT UNLESS MIXTURE USED. IDLE AND IDLE MIXTURE WERE WITHIN LIMITS. UNIT RETURNED FOR INSPECTION AND REPAIR. CARBURETOR WAS INSTALLED DUE TO PREVIOUS UNITS MIXTURE UNABLE TO SHUTDOWN CLEAN. MIXTURE CONTROL WAS FOUND TO BE WORN AND LEAKING FROM BODY OF UNIT. NO OTHER ENGINE PERFORMANCE ISSUES NOTED PRIOR TO ITS REMOVAL.