Yamaha YZ 2020 Series, Owner'S Service Manual

Page: 346 / 376

TROUBLESHOOTING
9-1
EAM20148
TROUBLESHOOTING
EAM30309
GENERAL INFORMATION
TIP
Troubleshooting information provided here does not cover all the trouble symptoms, possible causes,
and remedial actions. Some items may not apply depending on the model. Use this information as a
guide and quick reference matrix when performing basic troubleshooting. Refer to the each chapter for
detailed information on checking, adjustment, and replacement.
EAM30509
TROUBLESHOOTING OF ENGINE (fault code not detected)
TIP
If a fault code is detected, refer to the “FUEL INJECTION SYSTEM” on page 8-17.
Engine does not crank.
Engine will not start or is difficult to start, but it cranks.
Symptom Possible cause Actions
Starter motor does not operate
Refer to “TROUBLESHOOTING” under “ELECTRIC STARTING
SYSTEM” on page 8-5.
Starter motor operates, but the
engine does not crank.
Starter clutch malfunction Replace the starter clutch.
Improper oil grade (starter clutch
slipping)
Change to recommended engine
oil.
Stuck piston or seized crankshaft
Disassemble and check the
engine. Replace defective parts.
Symptom Possible cause Actions
Spark plug does not produce a
spark
Refer to “TROUBLESHOOTING” under “IGNITION SYSTEM” on page
8-1.
Fuel not supplied
— Measure the fuel pressure.
Empty fuel tank Fill the fuel tank with fuel.
Clogged fuel tank cap breather
hole
Clean the fuel tank cap.
Clogged or damaged fuel hose
Clean, repair, or replace the fuel
hose.
Fuel leakage
Check the fuel passage. Repair or
replace as necessary.
Clogged fuel pump Clean or replace the fuel pump.
Cracks or damage in fuel pump Replace the fuel pump.
Fuel pump malfunction
Refer to “TROUBLESHOOTING”
under “FUEL PUMP SYSTEM” on
page 8-41.
Failed or clogged fuel injector Replace the fuel injector.
ECU failure Replace the ECU.