Yamaha F250 LF250 - Manual (Page 57)

Maintenance
51
EMU30770
Cleaning and adjusting spark plug
WARNING
EWM00560
When removing or installing a spark plug,
be careful not to damage the insulator. A
damaged insulator could allow external
sparks, which could lead to explosion or
fire.
CAUTION:
ECM01510
● Do not use any tools to remove or install
the spark plug cap, otherwise the igni-
tion coil coupler may get damaged. The
spark plug cap may be difficult to re-
move because the rubber seal on the
end of the cap fits tightly. To remove the
spark plug cap, simply twist it back and
forth while pulling it out; to install it,
twist it back and forth while pushing it
in.
● Be sure to use the specified spark plug,
otherwise the engine may not operate
properly.
The spark plug is an important engine compo-
nent and is easy to inspect. 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 di-
agnose any problems yourself. Instead, take
the outboard motor to a Yamaha dealer. You
should periodically remove and inspect the
spark plug because heat and deposits will
cause the spark plug to slowly break down
and erode.
1. Remove the bolts that are securing the
ignition coil cover, and then remove the
cover.
2. Remove the bolts that are securing the
spark plug cap, and then remove the cap.
3. Remove the spark plug. If electrode ero-
sion becomes excessive, or if carbon and
other deposits are excessive, you should
replace the spark plug with another of the
correct type.
4. Before fitting the spark plug, measure the
electrode gap with a wire thickness
gauge; adjust the gap to specification if
necessary.
Standard spark plug:
LFR6A-11
U6P212E0.book Page 51 Monday, June 6, 2005 4:23 PM