Section X. MAINTENANCE OF AIR INTAKE, EXHAUST, AND BREATHER SYSTEMS

Section X. MAINTENANCE OF AIR INTAKE, EXHAUST,

AND BREATHER SYSTEMS

4-22. Description

a. Before it enters the engine, the intake air is

cleaned by an oil bath air cleaner. The air passes

through the oil cup of the air cleaner and entrains

droplets of oil. This oil is deposited in the air

cleaner filter element. As the air passes through the

filter element, dirt particles adhere to the oil

deposits in the filter element and are prevented

from entering the carburetor. The oil drains back

from the filter element into the oil cup, carrying

with it the dirt particles. As the oil cup is emptied

during servicing, the dirt particles are disposed of

with the waste oil. The air cleaner is stud mounted

on an elbow attached to the carburetor air inlet.

b. The exhaust gases from the engine are passed

through a muffler to decrease engine noise and to

prevent sparks from being discharged into the

atmosphere. Since this pumping assembly is

designed to pump flammable liquids, control of

sparks from the exhaust system is important. When

inspecting the muffler, make sure that its spark-

arresting characteristics are operative.

c. A breather vent is provided to prevent

pressure buildup within the engine. Internal crank-

case pressure can result from an increase of engine

temperature which causes the gas in the engine to

expand, or by blowby at the piston rings. By

allowing free passage of gas from the engine, this

pressure is relieved. A reed valve is incorporated in

the breather system to prevent a free flow of air into

the engine, so that when the piston is on the down

stroke and moves into the crankcase, air is expelled

through the breather. On the upstroke of the piston,

however, the reed valve prevents the air from

reentering the engine. This system maintains a

slight vacuum in the crankcase. This is desirable,

since it prevents air pressure from blowing the oil

out through the seals. A washable breather filter is

used in the system. This filter requires periodic

cleaning.

4-23. Air Cleaner

a. Removal and Disassembly

(1) Service the air cleaner as directed in

paragraph 3-9.

(2) Refer to figure 4-9 if further disassembly

of air cleaner related parts is required.

Figure 4-9. Air cleaner and related parts, exploded view.

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