Section 07 ELECTRICAL SYSTEM
Sub-Section 02 (IGNITION SYSTEM)
07-02-17
Fouling
Fouling of the spark plug is indicated by irregular
running of the engine, decreased engine speed
due to misfiring, reduced performance, and in-
creased fuel consumption. This is due to a loss of
compression. Other possible causes are: pro-
longed idling, or running on a too rich mixture due
to a faulty carburetor adjustment or incorrect fuel.
The plug face of a fouled spark plug has either a
dry coating of soot or an oily, glossy coating given
by an excess either of oil or of oil with soot. Such
coatings form a conductive connection between
the center electrode and ground.
Spark Plug Analysis
1. Overheated (light grey)
2. Normal (brownish)
3. Fouled (black)
The plug face (and piston dome) reveals the con-
dition of the engine, operating condition, method
of driving and fuel mixture. For this reason it is
advisable to inspect the spark plug at regular inter-
vals, examining the plug face (i.e. the part of the
plug projecting into the combustion chamber) and
the piston dome.
Spark Plug Installation
Prior to installation make sure that contact surfac-
es of the cylinder head and spark plug are free of
grime.
1. Using a wire feeler gauge, set electrode gap ac-
cording to the following chart.
2. Apply anti-seize lubricant over the spark plug
threads to prevent possible seizure.
3. Hand screw spark plug into cylinder head and
tighten with a torque wrench and a proper
socket.
1. Proper socket
2. Improper socket
Spark Plug Chart
NOTE:
Refer to next page for
Spark Plug Sym-
bol Explanation.
A00E0AA
123
Watercraft
model
Engine
Spark
plug
Torque
N•m (lbf•ft)
Gap
mm (inch)
SP 717D
NGK
BR7ES
24 (17)
0.5-0.6
(.020-.024)
GS/GSI/GTS/
GTI/HX
717
NGK
BR8ES
24 (17)
0.5-0.6
(.020-.024)
SPX/GSX/
GTX/XP
787
NGK
BR8ES
24 (17)
0.5-0.6
(.020-.024)
A00E0BA
2
1
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