2003 Ski-Doo ZX Series Factory Shop Manual, Page 71Get this manual
Section 03 TROUBLESHOOTING Subsection 02 (ENGINE)
SYMPTOM CONDITION TESTINSPECTION
IRREGULAR ENGINE IDLENORMAL USE AFTER ENGINE WARM UP1Check chokeaChoke plunger may be partially openedReadjust2Check carburetor adapteraAir enters through crackReplace3Check air screw positionaInadequate fuelair mixtureAdjust according to specifications (refer to TECHNICAL DATA)4Check dimension of pilot jetaInadequate fuelair mixtureAdjust according to specifications (refer to TECHNICAL DATA)5Check reed valveaImproper tightness andor openingReplace or adjustRefer to proper ENGINE subsection6Perform engine leak testaLeaking gaskets allow air to enter in engineReplace defective parts7DPM manifold air vent is obstructedaCarburetion is too leanEnsure proper air vent