Checking The Spark Plugs - Yamaha EK25BMH Service Manual

CHK
GENERAL
ADJ

CHECKING THE SPARK PLUGS

1. Check:
• Electrodes
Cracks/excessive wear → Replace.
• Insulator color
Distinctly different color → Check the
engine condition.
Color guide:
Medium to light tan color
Normal
Whitish color
• Lean fuel mixture
• Plugged jet (s)
• Wrong setting
Blackish color
• Rich mixture
• Excessive oil usage
• Defective ignition system
• Defective spark plug
2. Clean:
• Spark plug
(use a spark plug cleaner or wire
brush)
3. Check:
• Spark plug type
Incorrect → Replace.
Standard spark plug
NGK B7HS-10
4. Measure:
• Spark plug gap
Out of specification → Replace.
Spark plug gap
0.9-1.0 mm (0.035-0.039 in)
3-22
1
2
1
a
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