Inspecting Spark Plug - Yamaha LF250 Owner's Manual

Maintenance
EMU3077B

Inspecting spark plug

The spark plug is an important engine com-
ponent. The condition of the spark plug can
indicate something about the condition of the
engine. For example, if the center electrode
porcelain is very white, this could indicate an
intake air leak or carburetion problem in that
cylinder. Do not attempt to diagnose any
problems yourself. Instead, take the out-
board motor to a Yamaha dealer. You should
periodically remove and check the spark plug
because heat and deposits will cause the
spark plug to slowly break down and erode.
To remove the spark plug
1. Remove the bolts to remove the ECM
(Electronic control module) cover.
2
1
1. Bolt
2. ECM (Electronic Control Module) cover
2. Remove the bolts that are securing the
ignition coil, and then remove the ignition
coil. NOTICE: Do not use any tools to
remove or install the ignition coil. Oth-
erwise, the ignition coil coupler could
be damaged.
[ECM02331]
82
1
2
1. Bolt
2. Ignition coil
3. Remove the spark plug. WARNING!
When removing or installing a spark
plug, be careful not to damage the in-
sulator. A damaged insulator could al-
low external sparks, which could lead
to explosion or fire.
1
ZMU05160
To check the spark plug
1. Check the condition of the spark plug. If
electrode erosion becomes excessive or
carbon and other deposits are exces-
sive, replace the spark plug with the
specified plug.
Standard spark plug:
LFR6A-11
2. Measure the spark plug gap using a
thickness gauge. If the spark plug gap is
out of specification, replace the spark
plug with the specified plug.
ZMU05161
[EWM00562]
ZMU08486