Electrical Systems; Incorrect Engine Idling Speed; Engine; Fuel System - Yamaha XN125 2000 Service Manual

POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE

ELECTRICAL SYSTEMS

Battery
• Improperly charged battery
• Faulty battery
Fuse(s)
• Blown, damaged or incorrect fuse
• Improperly installed fuse
Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
Ignition coil
• Broken or shorted primary or secondary coils
• Faulty spark plug lead
• Cracked or broken ignition coil body
EAS00847

INCORRECT ENGINE IDLING SPEED

ENGINE

Cylinder and cylinder head
• Incorrect valve clearance
• Damaged valve train components
Air filter
• Clogged air filter element

FUEL SYSTEM

Carburetor
• Faulty starter plunger
• Loose or clogged pilot jet
• Loose or clogged pilot air jet
• Damaged or loose carburetor joint
• Improperly adjusted engine idling speed
(throttle stop screw)
• Improper throttle cable free play
• Flooded carburetor
Autochoke unit
• Faulty starter plunger
• Faulty ignitor unit
EAS00848
POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE
Refer to "STARTING FAILURE/HARD STARTING" section.
ENGINE
Air filter
• Clogged air filter element
STARTING FAILURE/HARD STARTING/
INCORRECT ENGINE IDLING SPEED/
Ignition system
• Faulty ignition unit
• Faulty pickup coil
• Broken generator rotor woodruff key/slipped
timing
Switches and wiring
• Faulty main switch
• Broken or shorted wiring
• Faulty front, rear or both brake switches
• Faulty start switch
• Improperly grounded circuit
• Loose connections
Starting system
• Faulty starter motor
• Faulty starter relay
• Faulty starter clutch
ELECTRICAL SYSTEMS
Battery
• Discharged battery
• Faulty battery
Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
Ignition coil
• Faulty spark plug lead
Ignition system
• Faulty ignitor unit
• Faulty pickup coil
FUEL SYSTEM
Carburetor
• Faulty diaphragm
• Incorrect fuel level
• Loose or clogged main jet
9-2
TRBL
SHTG