250
Section 4 Engine Service
valve similar to the one shown in Figure 13-18.
The valve allows outward airfl ow only.
Inspect the valve to make sure it is not dam-
aged or distorted. If it is, the breather assembly
must be replaced. If applicable, see that the drain
hole in the body of the assembly is open. This hole
permits accumulated oil to return to engine. After
all components have been inspected, replace dam-
aged gaskets, reinstall the assembly on the engine,
and tighten the screws.
Muffl er Service
An engine takes in large quantities of air mixed
with fuel, and then burns the mixture. Unless the
engine readily rids itself of the by-products of
combustion, its effi ciency will be greatly reduced.
This is the task of the exhaust system, which, in
small gasoline engines, mainly consists of exhaust
port(s) and a small muffl er.
A muffl er is designed to reduce noise and
allow exhaust gases to escape. When it becomes
clogged with carbon soot, gases cannot get out of
the combustion chamber quickly enough to allow
fresh air and fuel to enter. This causes a loss in
engine power, along with a tendency to overheat.
If clogging is suspected with a sealed muffl er,
install a new muffl er and check for improved engine
effi ciency. See Figure 13-19. If a muffl er is designed
to be taken apart, it can be disassembled and cleaned
in a solvent to remove soot and other debris.
Figure 13-17.
The foam pre-cleaner can be washed in detergent and
water and squeezed dry.
Figure 13-18.
Crankcase breather elements need periodic
inspection. The function of the reed valve is to allow air
to leave the crankcase, but prevent it from entering.
Valve Drain hole
Figure 13-19.
Locking tabs are often used to prevent muffl er fasteners
from loosening. A—Before attempting to remove the
fasteners, use a screwdriver to bend the tabs out of the
way. B—Once tabs are bent down, a wrench can be used
to remove the fasteners securing the muffl er to the engine.
Locking tab
A
B