Starting Failure/Hard Starting; Engine; Fuel System - Yamaha XN125 2000 Service Manual

EAS00845
NOTE:
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 manual
for checks, adjustments, and replacement of parts.

STARTING FAILURE/HARD STARTING

ENGINE

Cylinder and cylinder head
• Loose spark plug
• Loose cylinder head or cylinder
• Damaged cylinder head gasket
• Damaged cylinder base 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 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 FAILURE/HARD STARTING
TROUBLESHOOTING

FUEL SYSTEM

Fuel tank
• Empty fuel tank
• Clogged fuel tank cap breather hole
• Deteriorated or contaminated fuel
• Clogged or damaged fuel hose
Carburetor
• 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 adjusted pilot air screw
• Improperly installed pilot jet
• Clogged starter jet
• Clogged emulsion tube
Autochoke unit
• Faulty starter plunger
• Faulty ignitor unit
• Faulty thermo switch
9-1
TRBL
SHTG