Checking The Spark Plugs - Yamaha MTN850-AH Owner's Manual

Panel B
To remove the panel
1. Remove the bolts and washers.
1 2
1 2
1. Bolt
2. Washer
2. Pull the panel outward as shown.
Periodic maintenance and adjustment
1. Panel B
To install the panel
Place the panel in the original position,
and then install the washers and bolts.
8-10

Checking the spark plugs

The spark plugs are important engine
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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.
Specified spark plug:
NGK/CPR9EA9
EAU19653
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