Checking The Spark Plugs - Yamaha TDM850 Owner's Manual

PERIODIC MAINTENANCE AND MINOR REPAIR
1. Spark plug cap

Checking the spark plugs

The spark plugs are important engine
components, which are easy to check.
Since heat and deposits will cause any
6
spark plug to slowly erode, the spark
plugs 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.
To remove a spark plug
1. Remove cowling A. (See page 6-5
for cowling removal and installa-
tion procedures.)
2. Remove the spark plug cap.
1. Spark plug wrench
3. Remove the spark plug as shown
EAU01668
with the spark plug wrench includ-
ed in the owner's tool kit.
To check the spark plugs
1. Check that the porcelain insulator
around the center electrode on
each spark plug is a medium-to-
light tan (the ideal color when the
motorcycle is ridden normally).
2. Check that all spark plugs installed
in the engine have the same color.
NOTE:
@
If any 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 motorcycle.
@
3. Check each spark plug for elec-
6-7
trode erosion and excessive car-
bon or other deposits, and replace
it if necessary.
Specified spark plug:
DPR8EA-9 (NGK) or
X24EPR-U9 (DENSO)