Yamaha BEARTRACKER YFM250XC, Service Manual

Page: 306 / 398

TRBL
SHTG
9 - 2
STARTING FAILURE/HARD STARTING/POOR IDLE SPEED
PERFORMANCE/POOR MEDIUM AND HIGH-SPEED PERFORMANCE
COMPRESSION SYSTEM
Cylinder and cylinder head
●
Loose spark plug
●
Loose cylinder head or cylinder
●
Broken cylinder head gasket
●
Worn, damaged or seized cylinder
Piston and piston rings
●
Improperly installed piston ring
●
Worn, fatigued or broken piston ring
●
Seized piston ring
●
Seized or damaged piston
Valve, camshaft and crankshaft
●
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
●
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
Electrical system
●
Faulty spark plug
●
Faulty CDI unit
●
Faulty pickup coil
●
Faulty source coil
●
Faulty ignition coil
Valve train
●
Improperly adjusted valve clearance
Air filter
●
Clogged air filter element
POOR MEDIUM AND HIGH-SPEED PERFORMANCE
POOR MEDIUM AND HIGH-SPEED PERFORMANCE
Refer to “STARTING FAILURE/HARD STARTING” and “POOR IDLE SPEED PERFORMANCE-
VALVE TRAIN”.
Carburetor
●
Improper jet needle clip position
●
Improperly adjusted fuel level
●
Clogged or loose main jet
●
Deteriorated or contaminated fuel
Air filter
●
Clogged air filter element
9