2004 John Deer Buck Utility ATV 500, 500EX and 500EXT Service Manual, Page 38Get this manual
Clean carbon accumulation and replace spark plugGo to next stepElectrical system has failure? Replace defective part(s)Go to next stepCheck leakage on intake manifoldair filter boxAir leak on intake system? Retighten screws andor replace intake manifoldair filter boxGo to next stepCheck exhaust air leakingExhaust gasket is leaking? Retighten screws andor replace exhaust gasketGo to next stepIntake valve(s) is (are) leaking? Repair or replace valve(s)Go to next stepCheck if fuel supply is insufficient at high RPMFuel line is contaminated andor bent (engine gets lean)? Clean andor replace defective part(s)Go to next stepCheck calibration of carburetorWrong carburetor adjustment (engine to lean)? Clean and readjust carburetor Go to next stepReadjust carburetor andor replace spark plugGo to next stepCheck fuel supply to engine intakeFuel valve is switched off? Turn on fuel valveGo to next stepRun out of fuel? Turn fuel valve to "RES" position and refillGo to next stepPoor quality andor wrong fuel? Clean from contamination and use appropriate fuelGo to next stepFuel supply insufficient at high RPM? Clean fuel supply from contaminationGo to next stepCarburetor contaminated? Clean jets and carburetor float chamber from contaminationGo to next stepFuel line clogged andor bent? Clean fuel supply from contamination andor replace defective part(s)Go to next stepPerform engine leak testRefer to "Engine Leak Test" procedureCheck for possible piston seizureDamaged head gasket andor seal andor leaking inlet exhaust valve(s)? Replace andor repair defective partsGo to next stepPiston seizure (piston ring(s) damaged andor cylinder shows grooves)Spark plug heat range is too low? Replace damaged parts and install spark plug with appropriate heat rangeGo to next stepCompression ratio is too high?