1. GENERAL INFORMATION ATV 300/250 ENGINE LACKS POWER Inspection/Adjustment Symptom Probable Cause Start engine and accelerate lightly for observation Clogged air cleaner Engine speed Engine speed does not Restricted fuel flow increases increase sufficiently Clogged fuel tank cap breather hole Clogged exhaust muffler Check ignition timing Carburetor fuel level too low (using a timing light) Faulty ignition unit Correct timing Incorrect timing Faulty pulser coil Check valve clearance Improper valve clearance Correct Incorrect adjustment Excessively worn valve seat (protruded valve stem) Test cylinder compression Improper valve and seat contact Normal Abnormal Worn cylinder and piston rings compression compression Leaking cylinder head gasket Improper valve timing Check carburetor for clogging Not clogged Clogged Clean and unclog Remove spark plug and inspect Plug not fouled or Plug fouled or Fouled spark plug discolored discolored Incorrect heat range plug Remove oil dipstick and check oil level and condition Incorrect or Oil level too high Correct and not Oil level too low contaminated contaminated Oil not changed Remove cylinder head oil pipe bolt and inspect Valve train not Clogged oil line Valve train lubricated properly lubricated properly Faulty oil pump Check if engine overheats Coolant level too low Worn cylinder and piston rings Mixture too lean Engine does not Engine overheats Poor quality fuel overheats Excessive carbon build-up in combustion chamber Ignition timing too early Rapidly accelerate or run at high speed Excessive carbon build-up in combustion chamber Engine does not knock Engine knocks Poor quality fuel Clutch slipping Mixture too lean Ignition timing too early 1-22