Yamaha Aerox GDR155 Owner's Manual page 72

Periodic maintenance and adjustment
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 vehi-
cle is ridden normally).
TIP
If the spark plug shows a distinctly dif-
9
ferent color, the engine could be oper-
ating improperly. Do not attempt to
diagnose such problems yourself. In-
stead, have a Yamaha dealer check
the vehicle.
2. Check the spark plug for electrode
erosion and excessive carbon or
1
other deposits, and replace it if
necessary.
Specified spark plug:
NGK/CPR8EA9
3. Measure the spark plug gap with a
wire thickness gauge and, if nec-
essary, adjust the gap to specifi-
cation.
1. Spark plug gap
Spark plug gap:
0.8–0.9 mm (0.031–0.035 in)
To install the spark plug
1. Clean the surface of the spark
2. Install the spark plug with the
TIP
If a torque wrench is not available
when installing a spark plug, a good
estimate of the correct torque is 1/4–
1/2 turn past finger tight. However, the
spark plug should be tightened to the
specified torque as soon as possible.
3. Install the spark plug cap.
9-9
plug gasket and its mating sur-
face, and then wipe off any grime
from the spark plug threads.
spark plug wrench, and then tight-
en it to the specified torque.
Tightening torque:
Spark plug:
13 N·m (1.3 kgf·m, 9.4 lb·ft)