Checking The Spark Plugs - Yamaha TDM900 Owner's Manual

PERIODIC MAINTENANCE AND MINOR REPAIR
To install the cowling
Place the cowling in the original posi-
tion, and then install the screws and the
quick fastener.
1
NOTE:
To install the quick fastener, push the
2 center pin out so that it will protrude
from the fastener head, insert the fas-
tener into the cowling, and then push
3
the protruding pin in until it is flush with
the fastener head.
4
5
Panels A and B
To remove one of the panels
6
1. Remove the corresponding cowl-
ing A or B. (See page 6-5.)
7
2. Remove the
page 3-13.)
8
3. Remove the screw, and then take
the panel off.
9
1. Screw
To install the panel
1. Place the panel in the original po-
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sition, and then install the screw.
2. Install the seat and the cowling.
seat. (See
1
1. Panel A

Checking the spark plugs

1
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
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.
6-6
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