2003 Ski-Doo ZX Series Factory Shop Manual, Page 73Get this manual
Section 03 TROUBLESHOOTING Subsection 02 (ENGINE)
10Check if there are leaks at air intake silencer andor engine crankcaseaLeak(s)Repair or replace11Check condition and heat range of spark plugsaMelted spark plug tip or inadequate heat rangeReplaceSYMPTOM CONDITION TESTINSPECTION ENGINE EQUIPPED WITH RAVE VALVE DOES NOT REACH ITS FULL OPERATING RPM (500 TO 1000 RPM SLOWER)NORMAL USE1Check RAVE valve pistonsaValve piston(s) is (are) not screwed to the bottomScrew valve piston(s) to bottom2Check that valve moves freelyaValve stuck in closed positionClean3Check RAVE valve stemsaBent RAVE valve stem(s)Replace4Check RAVE valvesaJammed valve(s)Clean5Check tension of RAVE springsaInadequate spring tensionReplace6Check RAVE pressure holesaClogged holesClean7Check clamps or sleevesaDamaged clamp(s) or sleeve(s)Replace8Check exhaust tightnessaExhaust system is leaking leading to too low back pressureReplaces parts and reseal