- 51 -
10. TROUBLESHOOTING
The following three conditions must be fulfilled for satisfactory engine start.
1. The cylinder filled with a proper fuel-air mixture.
2. Good compression in the cylinder.
3. Good spark, properly timed, 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.
The most common causes of engine troubles are given below :
10-1 STARTING DIFFICULTIES
10-1-1 FUEL SYSTEM
(1) No gasoline in the fuel tank.
(2) The carburetor is not choked sufficiently especially when the engine is cold.
(3) Water, dust or gum in the gasoline interfering the fuel flow to the carburetor.
(4) Inferior grade gasoline or poor quality gasoline not vaporized enough to produce the correct fuel-air
mixture.
(5) 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 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 choke valve open during this operation.
Dry the spark plug well, screw it into place, and try to start again.
10-1-2 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 storage.
(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 compres-
sion stroke.
(4) Incorrect Valve 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.
Clean or replace the parts.
