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Section 4 Engine Service
clean it on a wire wheel or with a wire brush. If the
threads are dirty, they should be wiped clean or
wire brushed before inserting the plug back into
the spark plug hole. The gasket should be in good
condition or replaced with a new one.
Insert the spark plug in the spark plug hole and
turn it clockwise by hand until it stops. Be careful
not to cross thread the spark plug in the hole. If the
plug will not turn, do not force it. Remove it and
examine the threads in the hole. If they are dam-
aged, a thread chaser (special thread tapping tool)
may be needed to clean and correct the threads.
If the spark plug turns smoothly by hand until
it seats, tighten the plug with a torque wrench to
13–15 lb ft. Do not overtighten.
Examine the spark plug wire for deterioration
before reinstalling it on the spark plug. Heat and
dirt can make the insulation brittle and insula-
tion cracking can occur. Cracked wire insulation
can allow arcing to metallic parts of the engine
and cause hard starting and erratic running. Oil-
or fuel-soaked wires will leak current and cause
weak fi ring of the plug. The insulating boot should
be dry and in good condition.
Air Cleaner Service
The air cleaner should be cleaned before each
season of operation and at regular intervals there-
after. Under severe dust conditions, air fi lters
should be cleaned more often. A plugged air fi lter
can cause hard starting, loss of power, and spark
plug fouling.
Three types of air cleaners widely used in
small gasoline engines are the oil-wetted (plastic
foam element) type, the dry type (pleated paper
element), and the dual-element type. Each has a
different method of cleaning and servicing.
Begin by removing the screw, wing nut, or
other fastening device to uncover the air cleaner
element. See Figure 13-12.
When servicing an oil-wetted fi lter element,
the element can be pulled from the receptacle after
the cover is removed. See Figure 13-13. Be careful
not to drop any dirt into the carburetor throat dur-
ing this procedure.
To clean the element, wash it in liquid detergent
and water. Then rinse the element in clear water.
After washing the element, wrap it in dry cloth
and squeeze it dry. Absorbent toweling works well
for this procedure.
The plastic foam should be saturated with clean
engine oil. After saturating the element, squeeze
excess oil out of the foam. See Figure 13-14. Finally,
reassemble the air fi lter unit. Follow any special
instructions found in the owner’s manual for the
specifi c engine and fi lter.
Most dry-type air fi lter elements (pleated
paper) are designed to be thrown away when they
become dirty. Nevertheless, you can clean a pleated
paper fi lter element by tapping it on a fl at surface
to dislodge light accumulations of dirt. However, if
the element will not tap clean, it must be replaced.
Figure 13-12.
The cover on this air cleaner housing is held in place
by a screw.
Air cleaner cover
Figure 13-13.
After the cover is removed, the element can be pulled
from the receptacle.
Oil-wetted
air cleaner