Yamaha VMAX VMX12 Owner's Manual page 51

1. Spark plug wrench
2. Remove the spark plug as shown,
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.
PERIODIC MAINTENANCE AND MINOR REPAIR
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-
trode erosion and excessive car-
bon or other deposits, and replace
it if necessary.
Specified spark plug:
DPR8EA-9/NGK or
X24EPR-U9/DENSO
6-8
a. Spark plug gap
To install a spark plug
1. Measure the spark plug gap with a
wire thickness gauge and, if nec-
essary, adjust the gap to specifica-
tion.
Spark plug gap:
0.8–0.9 mm
2. Clean the surface of the spark
plug gasket and its mating sur-
face, and then wipe off any grime
from the spark plug threads.
3. Install the spark plug with the
spark plug wrench, and then tight-
en it to the specified torque.
6