Electrical - Yamaha YZ450F(D) Owner's Service Manual

ELECTRICAL

CHECKING THE SPARK PLUG
1. Remove:
• Spark plug
2. Inspect:
• Electrode "1"
Wear/damage → Replace.
• Insulator color "2"
Normal condition is a medium to
light tan color.
Distinctly different color → Check
the engine condition.
An extended run at low speeds
causes the insulator to be colored
black even if the air-fuel mixture is
normal.
3. Measure:
• Plug gap "a"
Use a wire gauge or thickness
gauge.
Out of specification → Regap.
Spark plug gap:
0.7–0.8 mm
(0.028–0.031 in)
4. Clean the plug with a spark plug
cleaner if necessary.
5. Tighten:
• Spark plug
Spark plug:
13 Nm (1.3 m•kg, 9.4
ft•lb)
• Before installing a spark plug, clean
the gasket surface and plug sur-
face.
• Finger-tighten "a" the spark plug
before torquing to specification "b".
CHECKING THE IGNITION TIMING
1. Remove:
• Timing mark accessing screw "1"
2. Attach:
• Timing light
• Digital tachometer
To the ignition coil lead (orange
lead "1").
Timing light:
YM-33277-A/90890-
03141
3. Adjust:
• Engine idling speed
Refer to "ADJUSTING THE EN-
GINE IDLING SPEED" section.
4. Check:
• Ignition timing
Visually check the stationary
pointer "a" is within the firing
range "b" on the rotor.
Incorrect firing range → Check ro-
tor and Crankshaft position sen-
sor.
5. Install:
• Timing mark accessing screw
Timing mark accessing
screw:
6 Nm (0.6 m•kg, 4.3
ft•lb)
3-24
ELECTRICAL