Checking The Spark Plugs - Yamaha Star XV19SY Owner's Manual

PERIODIC MAINTENANCE AND ADJUSTMENT

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
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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.
EAU19642
Specified spark plug:
NGK/DPR8EA-9
DENSO/X24EPR-U9
Before installing a spark plug, the spark
plug gap should be measured with a
wire thickness gauge and, if necessary,
adjusted to specification.
1. Spark plug gap
Spark plug gap:
0.8–0.9 mm (0.031–0.035 in)
Clean the surface of the spark plug
gasket and its mating surface, and then
wipe off any grime from the spark plug
threads.
TIP
If a torque wrench is not available when
installing a spark plug, a good estimate
of the correct torque is 1/4–1/2 turn
past finger tight. However, the spark
plug should be tightened to the speci-
fied torque as soon as possible.
7-8
Tightening torque:
Spark plug:
17.5 Nm (1.75 m·kgf, 12.7 ft·lbf)