11.
TRQU
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 dif-
ficult, 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:
11-1
STARTING
DIFFICULTIES
11-1-1
FUEL SYSTEM
7)
No
gasoline in th fuel tank;
or
the fuel cock is closed.
The carburetor is not choked enough, particularly when the engine is cold.
Water, dust
or
gum
in the gasoline block flow
of
the fuel to the carburetor.
Inferior grade gasoline or poor quality gasoline is not gasfied enough to produce the correct fuel-air mixture.
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)
Th~s
trouble may be remedied, depending on cases, by lightly tapping the float chamber with the grip of
a
screwdriver
of the like.
If the carburetor overflows, excessive fuel runs into the cyhder when starting the engine, making the fuel-air mixture
too rich to burn. If this happens, remove the spark plug, and turn the starting pulley 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.
When the engine is cold, pull the carburetor knob to let the gasoline
flow
into the carburetor.
11-1-2
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 compression
stroke during cranking.
3)
Damaged head gasket
or
loose cylinder head.
A
similar hissing noise is produced during compression stroke.
4)
Incorrect 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, and clean, remedy
or replace the parts.
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