Yamaha YZ450FN 2022, Owner'S Service Manual, Page: 329 / 366

ELECTRICAL COMPONENTS
8-48
a. Disconnect the diode from the wire har-
ness.
b. Connect the digital circuit tester (

) to the
diode coupler as shown.
c. Check the diode for continuity.
d. Check the diode for no continuity.
EAM30294
CHECKING THE IGNITION SPARK GAP
1. Check:
•
Ignition spark gap
Out of specification

Perform the ignition
system troubleshooting, starting with step (5).
Refer to “TROUBLESHOOTING” on page
8-3.
TIP
If the ignition spark gap is within specification,
the ignition system circuit is operating normally.
a. Remove the spark plug cap from the spark
plug.
b. Connect the ignition checker “1” as
shown.
c. Crank the engine, and measure the igni-
tion spark gap “a”.
d. Crank the engine, and gradually increase
the spark gap until a misfire occurs.
EAM30295
CHECKING THE SPARK PLUG CAP
1. Remove:
• Spark plug cap
(from the spark plug lead)
2. Check:
•
Spark plug cap resistance
Out of specification

Replace.
a. Connect the digital circuit tester (

) to the
spark plug cap.
No continuity
Positive tester probe 
Blue/Green “1”
Negative tester probe  Blue
“2”
Continuity
Positive tester probe  Blue “2”
Negative tester probe 
Blue/Green “1”
No continuity
Positive tester probe 
Brown/White, Brown “3”
Negative tester probe 
Blue/Green, Blue/White “4”
Continuity
Positive tester probe 
Blue/Green, Blue/White “4”
Negative tester probe 
Brown/White, Brown “3”
No continuity
Positive tester probe 
Blue/Black “5”
Negative tester probe

Blue/Red “6”
Continuity
Positive tester probe

Blue/Red “6”
Negative tester probe

Blue/Black “5”
A. Diode 1
B. Diode 2
C. Diode 3
L/G
L
L/B
L/R
Br/W,Br
L/G,
L/W
1
2
3
4
5
6
Minimum ignition spark gap
6.0 mm (0.24 in)
Ignition checker
90890-06754
Oppama pet–4000 spark checker
YM-34487
2. Spark plug cap
Resistance
7.50–12.50 k
