Yamaha MAJESTY YP400A - Checking the Spark Plug

PERIODIC MAINTENANCE AND ADJUSTMENT
7-12
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EAU34172
Checking the spark plug
The spark plug is an important engine
component, which is easy to check.
Since heat and deposits will cause any
spark plug to slowly erode, the spark
plug should be removed and checked
in accordance with the periodic mainte-
nance and lubrication chart. In addition,
the condition of the spark plug can re-
veal the condition of the engine.
To remove the spark plug
1. Open the rider seat. (See
page 4-12.)
2. Pull up the storage compartment
mat, and then remove the spark
plug cover by removing the
screws.
3. Remove the spark plug cap.
4. Remove the spark plug as shown,
with the spark plug wrench includ-
ed in the owner’s tool kit.
To check the spark plug
1. Check that the porcelain insulator
around the center electrode of the
spark plug is a medium-to-light tan
(the ideal color when the vehicle is
ridden normally).
TIP
If the spark plug shows a distinctly dif-
ferent color, the engine could be oper-
ating improperly. Do not attempt to
diagnose such problems yourself. In-
stead, have a Yamaha dealer check
the vehicle.
2. Check the spark plug for elec-
trode erosion and excessive car-
bon or other deposits, and replace
1. Storage compartment mat
2. Spark plug cover
3. Screw
1. Spark plug cap
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2
3
1
1. Spark plug wrench
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