Yamaha YZ450F(B) 2012 Owner's Service Manual page 187

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.
(couplers, leads and ignition coil)
OK ↓
Check engine stop switch.
OK ↓
Check ignition coil. (primary coil and secondary
coil)
OK ↓
Check AC magneto. (crankshaft position sensor
and stator coil)
OK ↓
Replace ECU.
*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-03112-C/90890-03112
Spark → • *Clean or replace spark plug.
• Check the connection of the spark plug cap to the
spark plug.
No good →
Repair or replace.
No good → Replace.
No good →
Replace.
No good →
Replace.
7-3
IGNITION SYSTEM