Starting Failure/Hard Starting; Fuel System; Electrical System - Yamaha YFZ450S 2003 Service Manual

EBS00537
NOTE:
_
The following troubleshooting does not cover all the possible causes of trouble. It should be helpful,
however, as a guide to troubleshooting. Refer to the relative procedure in this manual for check,
adjustment and replacement of parts.

STARTING FAILURE/HARD STARTING

FUEL SYSTEM

Fuel tank
• Empty
• Clogged fuel strainer
• Clogged fuel tank breather hose
• Deteriorated or contaminated fuel
Fuel cock
• Clogged fuel hose
Carburetor
• Deteriorated or contaminated fuel
• Clogged pilot jet
• Clogged pilot air passage
• Sucked-in air
• Deformed float
• Worn needle valve
• Improperly sealed valve seat
• Improperly adjusted fuel level
• Improperly set pilot jet
• Clogged starter jet
• Choke valve malfunction
Air filter
• Clogged air filter element
STARTING FAILURE/HARD STARTING
TROUBLESHOOTING

ELECTRICAL SYSTEM

Spark plug
• Improper plug gap
• Worn electrodes
• Wire between terminals broken
• Improper heat range
Ignition coil
• Broken or shorted primary/secondary
• Faulty ignition coil lead
• Broken body
C.D.I. system
• Faulty C.D.I. unit
• Faulty pickup coil
• Faulty lighting coil
• Faulty charging coil
• Broken woodruff key
Switches and wiring
• Faulty main switch
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty neutral switch
• Faulty start switch
• Faulty clutch switch
• Faulty throttle switch
• Faulty carburetor switch
• Loose connections
Starter motor
• Faulty starter motor
• Faulty starter relay
• Faulty starting circuit cut-off relay
• Faulty starter clutch
• Faulty torque limiter
Battery
• Faulty battery
• Discharged battery
9 - 1
TRBL
SHTG