1997 Yamaha YFM600FWAK ATV Service Manual, Page 313Get this manual
STARTING FAILUREHARD STARTINGPOOR IDLE SPEED PERFORMANCEPOOR MEDIUM AND HIGH SPEED PERFORMANCE COMPRESSION SYSTEM Cylinder and cylinder head
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Valve, camshaft and crankshaft
Loose spark plug Loose cylinder head or cylinder Broken cylinder head gasket Worn, damaged or seized cylinder Improperly installed piston ring Worn, fatigued or broken piston ring Seized piston ring Seized or damaged piston
Piston and piston rings
Improperly sealed valve Improperly contacted valve and valve seat Improper valve timing Broken valve spring Seized camshaft Seized crankshaft
POOR IDLE SPEED PERFORMANCE
POOR IDLE SPEED PERFORMANCE Carburetor Electrical system
Improperly returned starter plunger Loose pilot jet Clogged pilot jet Clogged pilot air jet Improperly adjusted idle speed (Throttle stop screw) Improper throttle cable play Flooded carburetor