Checking The Spark Plug - Yamaha MAJESTY 400 Owner's Manual

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
page 3-11.)
2. Pull up the storage compartment
mat, and then remove the spark
plug cover by removing the
screws.
PERIODIC MAINTENANCE AND MINOR REPAIR
EAU34171
2
1. Storage compartment mat
2. Spark plug cover
3. Screw
seat. (See
3. Remove the spark plug cap.
1
1. Spark plug cap
4. Remove the spark plug as shown,
with the spark plug wrench includ-
ed in the owner's tool kit.
3
(×3)
1
6-12
1
1. Spark plug wrench
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).
NOTE:
If the spark plug shows a distinctly dif-
ferent color, the engine could be defec-
tive. Do not attempt to diagnose such
problems yourself. Instead, have a
Yamaha dealer check the vehicle.
2. Check the spark plug for electrode
erosion and excessive carbon or
other deposits, and replace it if
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