TROUBLESHOOTING
9-2
Incorrect idling speed or mid-to-high speed
Compression pressure is low
—
Measure the compression pres-
sure.
Loose spark plug
Tighten the spark plugs to the
specified torque.
Loose cylinder head or cylinder
Tighten bolts or nuts on cylinder
head and cylinder to the specified
torque.
Damaged cylinder head gasket
Replace the cylinder head gasket.
Worn, damaged, or stuck piston
ring
Replace the piston and piston
rings as a set.
Seized or damaged piston
Replace the piston and piston
rings as a set.
Worn or damaged cylinder bore
Replace the cylinder, piston, and
piston rings as a set.
Symptom
Possible cause
Actions
Spark plug does not produce a
spark
Incorrect spark plug gap
Adjust the spark plug gap.
Worn or damaged spark plug
Replace the spark plug.
Defective spark plug cap
Replace the spark plug cap.
Defective ignition coil
Replace the ignition coil.
CDI unit failure
Replace the CDI unit.
Fuel not supplied
Fuel leakage
Check the fuel passage. Repair or
replace as necessary.
Clogged carburetor fuel passage
Clean the carburetor.
Clogged needle valve or needle
valve seat
Clean the needle valve or needle
valve seat.
Damaged float
Replace the float.
—
Water or foreign material in fuel,
degraded fuel
Change fuel.
Clogged carburetor air passage
Clean the carburetor.
Incorrectly adjusted throttle cable
Adjust the throttle grip free play.
Incorrectly adjusted idling speed
(throttle stop screw)
Adjust the throttle stop screw.
Incorrectly adjusted pilot screw
Adjust the pilot screw.
Incorrectly adjusted pilot air screw Adjust the pilot air screw.
Clogged pilot jet
Clean the pilot jet.
Loose pilot jet
Tighten the pilot jet to the specified
torque.
Damaged or worn needle valve
seat
Replace the needle valve seat.
Loose needle valve seat
Tighten the needle valve seat to
the specified torque.
Symptom
Possible cause
Actions
Summary of Contents for YZ125X 2022
Page 5: ...EAM20162 YAMAHA MOTOR CORPORATION U S A YZ MOTORCYCLE LIMITED WARRANTY ...
Page 8: ......
Page 10: ......
Page 38: ...MOTORCYCLE CARE AND STORAGE 1 26 ...
Page 54: ...CABLE ROUTING DIAGRAM 2 15 EAM20152 CABLE ROUTING DIAGRAM Frame and engine left side view ...
Page 56: ...CABLE ROUTING DIAGRAM 2 17 Frame and engine right side view ...
Page 58: ...CABLE ROUTING DIAGRAM 2 19 Handlebar front view 0 in 0 mm 0 mm 0 in ...
Page 60: ...CABLE ROUTING DIAGRAM 2 21 Rear brake right side view ...
Page 62: ...CABLE ROUTING DIAGRAM 2 23 ...
Page 90: ...ELECTRICAL SYSTEM 3 26 ...
Page 158: ...CHAIN DRIVE 4 66 ...
Page 202: ...CRANKSHAFT 5 42 seal lip 4 1 2 3 M ...
Page 226: ...CARBURETOR 7 11 ...
Page 231: ...ELECTRICAL COMPONENTS 8 4 EAM30289 CHECKING THE SWITCHES 1 1 Engine stop switch ...
Page 236: ...ELECTRICAL COMPONENTS 8 9 ...
Page 250: ...TROUBLESHOOTING 9 13 ...
Page 268: ......