Periodic maintenance and adjustment
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EAU67110
Checking the spark plugs
The spark plugs are important engine
components, which should be checked
periodically, preferably by a Yamaha
dealer. Since heat and deposits will
cause any spark plug to slowly erode,
they should be removed and checked
in accordance with the periodic mainte-
nance and lubrication chart. In addition,
the condition of the spark plugs can re-
veal the condition of the engine.
The porcelain insulator around the cen-
ter electrode of each spark plug should
be a medium-to-light tan (the ideal color
when the vehicle is ridden normally),
and all spark plugs installed in the en-
gine should have the same color. If any
spark plug shows a distinctly different
color, the engine could be operating im-
properly. Do not attempt to diagnose
such problems yourself. Instead, have
a Yamaha dealer check the vehicle.
If a spark plug shows signs of electrode
erosion and excessive carbon or other
deposits, it should be replaced.
Before installing a spark plug, the spark
plug gap should be measured with a
wire thickness gauge and, if necessary,
adjusted to specification.
Clean the surface of the spark plug
gasket and its mating surface, and then
wipe off any grime from the spark plug
threads.
NOTICE
ECA10841
Do not use any tools to remove or in-
stall the spark plug cap, otherwise
the ignition coil coupler may get
damaged. The spark plug cap may
be difficult to remove because the
rubber seal on the end of the cap fits
tightly. To remove the spark plug
cap, simply twist it back and forth
while pulling it out; to install it, twist
it back and forth while pushing it in.
Specified spark plug:
NGK/LMAR9E-J
1. Spark plug gap
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
Tightening torque:
Spark plug (new):
18 N·m (1.8 kgf·m, 13 lb·ft)
Spark plug (after checking):
13 N·m (1.3 kgf·m, 9.6 lb·ft)
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BX4-9-E1_1.book 11 ページ ２０１８年４月２７日 金曜日 午後４時３分
