Checking The Spark Plug - Yamaha AG100FA Owner's Manual

PERIODIC MAINTENANCE AND ADJUSTMENT

Checking the spark plug

The spark plug is an important engine
component, which is easy to check.
1
Since heat and deposits will cause any
spark plug to slowly erode, the spark
2
plug should be removed and checked
in accordance with the periodic mainte-
3
nance and lubrication chart. In addition,
the condition of the spark plug can re-
veal the condition of the engine.
4
To remove the spark plug
5
1. Remove the spark plug cap.
6
1
7
8
9
1. Spark plug cap
2. Remove the spark plug as shown,
with the spark plug wrench includ-
ed in the owner's tool kit.
EAU19604
1
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 vehicle is
ridden normally).
TIP
If the spark plug shows a distinctly dif-
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
other deposits, and replace it if
3. Measure the spark plug gap with a
1. Spark plug gap
To install the spark plug
1. Clean the surface of the spark plug
2. Install the spark plug with the
7-8
necessary.
Specified spark plug:
NGK/B7ES
wire thickness gauge and, if nec-
essary, adjust the gap to specifica-
tion.
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
gasket and its mating surface, and
then wipe off any grime from the
spark plug threads.