Checking The Spark Plug - Yamaha WR250R Owner's Manual

Checking the spark plug

The spark plug is an important engine
component, which should be checked
periodically, preferably by a Yamaha
dealer. Since heat and deposits will
cause any spark plug to slowly erode, it
should be removed and checked in ac-
cordance with the periodic mainte-
nance and lubrication chart. In addition,
the condition of the spark plug can re-
veal the condition of the engine.
The porcelain insulator around the cen-
ter electrode of the spark plug should
be a medium-to-light tan (the ideal color
when the vehicle is ridden normally). If
the spark plug shows a distinctly differ-
ent color, the engine could be operating
improperly. Do not attempt to diagnose
such problems yourself. Instead, have
a Yamaha dealer check the vehicle.
If the spark plug shows signs of elec-
trode erosion and excessive carbon or
other deposits, it should be replaced.
Specified spark plug:
NGK/CR9EK
Before installing a spark plug, the spark
plug gap should be measured with a
Periodic maintenance and adjustment
EAU48341 wire thickness gauge and, if necessary,
adjusted to specification.
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1. Spark plug gap
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
Clean the surface of the spark plug
gasket and its mating surface, and then
wipe off any grime from the spark plug
threads.
Tightening torque:
Spark plug:
13 Nm (1.3 m·kgf, 9.4 ft·lbf)
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.
NOTICE
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.
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ECA10841
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