Yamaha VMX12 2001 Service Manual page 448

EAS00844
NOTE:
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The following guide for troubleshooting does not cover all the possible causes of trouble. It should
be helpful, however, as a guide to basic troubleshooting. Refer to the relative procedure in this man-
ual for checks, adjustments, and replacement of parts.
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STARTING PROBLEMS
ENGINE
Cylinder(s) and cylinder head(s)
• Loose spark plug
• Loose cylinder head
• Damaged cylinder head gasket
• Worn or damaged cylinder
• Incorrect valve clearance
• Improperly sealed valve
• Incorrect valve-to-valve-seat contact
• Incorrect valve timing
• Faulty valve spring
• Seized valve
Piston(s) and piston ring(s)
• Improperly installed piston ring
• Damaged, worn or fatigued piston ring
• Seized piston ring
• Seized or damaged piston
Air filter
• Improperly installed air filter
• Clogged air filter element
Crankcase and crankshaft
• Improperly assembled crankcase
• Seized crankshaft
STARTING PROBLEMS
TROUBLESHOOTING
FUEL SYSTEM
Fuel tank
Fuel pump
Carburetor(s)
9 - 1
• Empty fuel tank
• Clogged fuel filter
• Clogged fuel strainer
• Clogged fuel tank drain hose
• Clogged rollover valve
• Clogged rollover valve hose
• Deteriorated or contaminated fuel
• Faulty fuel pump
• Faulty fuel pump relay
• Deteriorated or contaminated fuel
• Clogged pilot jet
• Clogged pilot air passage
• Sucked-in air
• Damaged float
• Worn needle valve
• Improperly installed needle valve seat
• Incorrect fuel level
• Improperly installed pilot jet
• Clogged starter jet
• Faulty starter plunger
• Improperly adjusted starter cable
TRBL
SHTG