G643(E) Service Manual Chapter 4. Engine Electrical System 117
Inspection of Spark Plug
Inspection and clean
1. Disconnect the ignition wires from the ignition
coil ass’y.
2. Remove all spark plugs from the cylinder head
using a spark plug wrench.
CAUTION
Take care not to come foreign materials into
spark-plug mounting hole.
3. Check the spark plug as below.
1) Insulator broken
2) Terminal worn
3) Carbon deposit
4) Gasket damaged or broken
5) Porcelain insulator of spark plug clearance
4. Check the plug clearance using a plug clearance
auge and if the value is not within the specified
values, adjust it by bending the ground clearance.
When installing a new sparkplug, install it after
checking the uniform plug clearance.
Spark plug clearance 0.8 ~ 0.9 mm
5. Install the spark plug and tighten it to the specified
torque.
Take care not to over tighten it to prevent cylinder
head threads from damage.
Tightening torque 30 N· m
Spark Plug Analysis
State
Contact point
is black
Contact point
is white
Description
• Density of the
fuel mixture
is thick
• Density of the
fuel mixture is
thin
• Lack of air
intake
• Ignition timing
is fast
• Spark plug is
tight
• Lack of torque
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