Yamaha YZ125(D) Owner's Service Manual page 153

IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to ignition system failure
and for checking the spark plug which will not spark.
Spark gap test
No spark ↓
Check entire ignition system for connection.
OK ↓
Check engine stop switch.
OK ↓
Check ignition coil. (primary coil and secondary
coil)
OK ↓
Check spark plug cap.
OK ↓
Check CDI magneto. (pickup coil and charging
coil)
OK ↓
Replace CDI unit.
*marked: Only when the ignition checker is used.
• Remove the following parts before inspection.
1. Seat
2. Fuel tank
• Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754
Pocket tester:
YU-3112-C/90890-03112
Spark → *Clean or replace spark plug.
No good → Repair or replace.
No good → Replace.
No good →
Replace.
No good → Replace.
No good →
Replace.
6-3
IGNITION SYSTEM