What was found
DURING 100-HOUR INSPECTION, NOTICED FUEL STAINS ON GASCOLATOR BOWL. REPLACED GASKET BETWEEN BOWL AND COVER, BUT COULD NOT SEAL. FURTHER INSPECTION WITH A STRAIGHT EDGE REVEALED COVER WAS BOWED, NOT FLAT AT MATING SURFACE. SUSPECT CAUSE: MANY YEARS OF OVERTIGHTENING THE BALE WIRE. FOUND SAME CONDITION ON 2 OTHER PA28140 AIRCRAFT. REPLACED GASCOLATOR COVERS. RECOMMEND AN INITIAL AND EACH 500 HOURS, INSPECTION OF MATING SURFACES WITH A STRAIGHT EDGE.