12.
TROUBLE
SHOOTING
The following three conditions must be satisfied for satisfactory engine start.
1.
The cylinder filled with a proper fuel-air mixture.
2. An appropriate compression in the cylinder.
3.
Good sparks at the correct time to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors which make
engine start difficult, e. g., a heavy load on the engine when it is about to start at low speed, and a high back
pressure due
to
a long exhaust pipe, just to say
a
few.
The most common causes
of
engine troubles are given below:
12-1
STARTING
DIFFICULTIES
12-
1
-
1
FUEL
SYSTEM
1)
No
gasoline in the fuel tank; or the fuel cock is closed.
2)
The carburetor is not choked enough, particularly when the engine is cold.
3)
Water, dust or gum
in
the gasoline block flow
of
the fuel to the carburetor.
4)
Inferior grade gasoline or poor quality gasoline is not gasfied enough to produce the correct fuel-air
5)
The carburetor needle valve is held open by dirt or gum.
This
trouble can be detected as the fuel
flows
out of the carburetor when the engine is idling. (Overflow)
This trouble may be remedied, depending on cases, by lightly tapping the float chamber with the grip
of
a screwdriver
of
the like.
r
6)
If the carburetor overflows, excessive fuel runs into the cylinder when starting the engine, making the
fuel-air mixture too rich to burn. If this happens, remove the spark plug, and pull the recoil starter a few
turns in order to let the rich fuel-air mixture out of the spark plug hole into the atmosphere. Keep the
carburetor choke open during this operation.
Dry
the spark plug well, screw it into place, and
try
to start
again.
mixture.
12-
1
-
2
COMPRESSION
SYSTEM
If starting difficulties and
loss
of
power are not due
to
the fuel system or ignition system, the following must
be checked for possible lack of compression.
1)
Engine inside is completely dried up because of a long period of non-operation.
2)
Loose
or
broken spark plug.
This
causes a hissing noise made
by
mixture gas running out
of
cylinder in
3)
Damaged head gasket or loose cylinder head. A similar hissing noise
is
produced during compression
4)
In correct Tappet Clearance
If the correct compression is not obtained even after remedying the above, disassemble the engine and
check further as follows:
a)
Valve stuck open due to carbon or gum
on
the valve stem.
b) If the piston rings are stuck
on
the piston, remove the piston and connecting rod from the engine,
compression stroke during cranking.
stroke.
and clean, remedy or replace the parts.
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34
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