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UF4D14E0.book Page 64 Tuesday, March 27, 2018 1:02 PM

Maintenance

EJU3437B
Checking the spark plugs TIP:
EWJ00351 When the engine is operating normally, the
WARNING color of the spark plug electrode portion will
Be careful not to damage the insulator be a medium-to-light tan.
when removing or installing a spark plug.
A damaged insulator could allow sparks to
escape, which could result in a fire or ex-
plosion.

Remove and check the condition of the spark
plugs.
The condition of a spark plug can indicate
something about the condition of the engine.
For example, if the center electrode portion is
very white, this could indicate an intake air 1 Insulator
leak or carburetion problem in that cylinder. 2 Electrode
Do not attempt to diagnose any problems 3 Spark plug gap
yourself. Have a Yamaha dealer service the
Specified spark plug:
watercraft. B7HS
To remove a spark plug: Spark plug gap:
(1) Remove the hood. (See page 27 for hood 0.6–0.7 mm (0.024–0.028 in)
removal and installation procedures.)
(2) Remove the spark plug cap. To install a spark plug:
(3) Remove the spark plug, and then check (1) Wipe off any dirt from the threads, insu-
the condition of the spark plug and the lator, and gasket surface of the spark
spark plug gap. If the electrode portion is plug.
significantly discolored, if electrode ero- (2) Install the spark plug, and then tighten it
sion becomes excessive, if carbon and to the specified torque.
other deposits are excessive, or if the
Tightening torque:
spark plug gap is not within the specified Spark plug:
range, replace the spark plug. 25 N·m (2.5 kgf·m, 18 lb·ft)

TIP:
If a torque-wrench is not available when you
are reinstalling a spark plug, a good estimate
of the correct torque is 1/12 turn past finger-
tight. When you are installing a new spark
plug, a good estimate of the correct torque is
1/2 to 2/3 turn past finger-tight.
(3) Wipe off any water or dirt inside the
spark plug cap.

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