A SMOKY, BLACK EXHAUST. Indicates a
unit contains a reservoir of oil and a filter element made
of metal gauze or fine metal wool. Air entering the
very rich fuel-air mixture.
cleaner passes through the opening at the top of the
STALLING OF THE ENGINE AS IT
body. The air flows past the oil-filled reservoir picking
WARMS. Could be caused by a defective choke
up particles of oil and carrying them into the filter. The
or closed choke valve.
filter traps the oil and particles and allows the oil to seep
back to the reservoir. The air finally hits the cover plate
A BACKFIRING ENGINE. May be due to an
and is deflected down through a passage to the
incorrect, often lean, fuel-air mixture reaching
carburetor.
the engine. In turn, this condition could be
caused by clogged fuel lines or a fluctuating fuel
The metal gauze or threads in the filter also act as a
level.
flame arrester in case of severe flashback or backfire.
Many air cleaners are equipped with a silencing unit
The more stubborn troubles in a carburetor can
called the "sound neutralizing chamber." It consists of
sometimes be eliminated only with its disassembly and
air-intake passages designed to muffle air noises and a
overhauling. The procedures vary according to the
felt pad that acts as a gasket and absorbs engine intake
manufacturer's specifications, which you should follow
noises.
closely.
The dry-type air cleaner (fig. 4-23) uses a treated
AIR CLEANERS
and pleated paper cleaner element, which requires
periodic replacement. The element is sealed in the air
The air cleaner is placed at the air entrance of the
breather by pressure against the rubberized material
carburetor to remove dust and other foreign matter from
bonded to the filter element and the cover plate and
the air before it enters the carburetor. A great deal of air,
housing. This type of air cleaner element is gradually
as much as 100,000 cubic feet for every 1,000-vehicle
replacing the oil-bath type because of its ability to
miles, is introduced into the engine. Without an air
remove smaller particles from the airflow into the
cleaner, dust and grit would enter the engine with the air
engine.
and would cause excessive wear and operating troubles.
A clogged air cleaner produces an action similar to
Two types of air cleaner are used: a wet type and a dry
choking that results in too rich a fuel mixture. Foreign
type.
matter passed into the engine because of a poor cleaner
The wet-type air cleaner (fig. 4-22) is an oil-bath
will also cause excessive engine wear and operating
cleaner, which consists of a main body and a cover. This
troubles.
ELEMENT GASKET
COVER
WING NUT
COVER GASKET
FILTER
ELEMENT
OIL
RESERVOIR
THROAT GASKET
CLAMP
TO CARBURETOR
ASf04022
CLAMP SEAL
Figure 4-22.--Wet-type air cleaner.
4-14
