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49
EMU28951
Cleaning and adjusting spark plug
WARNING
EWM00560
When removing or installing a spark plug,
be careful not to damage the insulator. A
damaged insulator could allow external
sparks, which could lead to explosion or
fire.
The spark plug is an important engine compo-
nent and is easy to inspect. The condition of
the spark plug can indicate something about
the condition of the engine. For example, if the
center electrode porcelain is very white, this
could indicate an intake air leak or carburetion
problem in that cylinder. Do not attempt to di-
agnose any problems yourself. Instead, take
the outboard motor to a Yamaha dealer. You
should periodically remove and inspect the
spark plug because heat and deposits will
cause the spark plug to slowly break down
and erode. If electrode erosion becomes ex-
cessive, or if carbon and other deposits are
excessive, you should replace the spark plug
with another of the correct type.
Before fitting the spark plug, measure the
electrode gap with a wire thickness gauge;
adjust the gap to specification if necessary.
When fitting the plug, always clean the gasket
surface and use a new gasket. Wipe off any
dirt from the threads and screw in the spark
plug to the correct torque.
NOTE:
If a torque-wrench is not available when you
are fitting a spark plug, a good estimate of the
correct torque is 1/4 to 1/2 a turn past finger-
tight. Have the spark plug adjusted to the cor-
rect torque as soon as possible with a torque-
wrench.
EMU28962
Checking fuel system
WARNING
EWM00060
Gasoline and its vapors are highly flam-
mable and explosive. Keep away from
sparks, cigarettes, flames, or other sourc-
es of ignition.
WARNING
EWM00910
Leaking fuel can result in fire or explosion.
Standard spark plug:
LFR5A-11
1. Spark plug gap
2. Spark plug I.D. mark (NGK)
Spark plug gap:
1.0–1.1 mm (0.039–0.043 in)
Spark plug torque:
25.0 Nm (18.4 ft-lb) (2.55 kgf-m)
U69J14E0.book Page 49 Friday, March 12, 2004 10:20 AM