2009 Suzuki 400 LTZ Quad Sport Service Manual, Page 73Get this manual
1A-9 Engine General Information and Diagnosis: Condition Possible cause Engine lacks power Loss of tappet clearance(Defective engine internal Weakened valve springselectrical parts) Valve timing out of adjustmentWorn piston rings or cylinderPoor seating of valvesFouled spark plugIncorrect spark plugClogged fuel injectorTP sensor out of adjustmentClogged air cleaner elementSucking air from throttle valve or vacuum hoseToo much engine oilDefective fuel pump or ECMDefective CKP sensor and ignition coilEngine lacks power Low fuel pressure(Defective control circuit Defective TP sensoror sensor) Defective IAT sensorDefective CKP sensorDefective IAP sensorDefective GP sensorDefective ECMTP sensor out of adjustmentEngine overheats Heavy carbon deposit on piston crown(Defective engine internal Not enough oil in the engineparts) Defective oil pump or clogged oil circuitUse of incorrect engine oilSucking air from intake pipeDefective cooling systemEngine overheats (Lean fuelair mixture) Short-circuited IAP sensorlead wireShort-circuited IAT sensorlead wireSucking air from intake pipe jointDefective fuel injectorDefective ECT sensorIgnition timing too advanced due to defective timing advance system (ECT sensor, GP sensor, CKP sensor and ECM Drive chain is too tightWorn piston rings or cylindersToo much engine oil in the engineWorn valve guidesScored or scuffed cylinder wallWorn valves stemsDefective stem sealsWorn oil ring side railsCorrectionReference Item AdjustReplaceAdjustReplaceRepairClean or replaceAdjust or replaceCleanAdjustCleanRetighten or replaceDrain out excess oilReplaceReplaceRepair or replaceReplaceReplaceReplaceReplaceReplaceReplaceAdjustCleanAdd oilReplace or cleanChangeRetighten or replaceRefer to "Engine Cooling Symptom Diagnosis in Section 1F (Page 1F-4)"Repair or replaceRepair or replaceRepair or replaceReplaceReplaceReplace Engine overheats (The other factors)