2008 Yamaha Raptor 250SE / 250SE2 Factory Service Manual, Page 303Get this manual
STARTING FAILUREHARD STARTINGPOOR IDLE SPEED PERFORMANCEPOOR MEDIUM AND HIGH-SPEED PERFORMANCE COMPRESSION SYSTEM Cylinder and cylinder head Loose spark plug Loose cylinder head or cylinder Broken cylinder head gasket Broken cylinder gasket Worn, damaged or seized cylinder Valve and camshaft Improperly sealed valve Improperly contacted valve and valve seat Improper valve timing Broken valve spring Seized camshaft
TRBL SHTG
Piston and piston rings Improperly installed piston ring Worn, fatigued or broken piston ring Seized piston ring Seized or damaged piston Crankcase and crankshaft Improperly seated crankcase Seized crankshaft Valve train Improperly adjusted valve clearance Improperly adjusted valve timing
EBS00538
POOR IDLE SPEED PERFORMANCE