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ABNORMAL COMBUSTION
The abnormal noises and other noises caused by abnormal combustion in the engine are classified as follows:
Knocking
On sudden acceleration, or when the accelerator pedal is fully depressed, a high pitched "ping ping" knocking
sound is heard. This has a bad effect on the piston and valves, and will also damage the engine.
Run on
Even after the ignition key switch has been turned OFF, combustion continues in the combustion chamber, and
the engine continues to run erratically.
After fire
When travelling for a long time under engine braking, or when the accelerator pedal is suddenly released, a loud
"bang" is heard due to an explosion in the exhaust system, with flame being visible around the muffler.
Back fire
The combustion does not complete within the explosion cycle, and continues until the intake valve opens for the
next cycle, igniting the air-fuel mixture while it is still being intaken. This causes a back fire, in which the air-fuel
mixture in the intake manifold or carburetor explode.
Knocking
Run on
Classification
Ignition
i
I
Phenomenon
I
Main places for inspection and adjustment
I
Main places for inspection and adjustment
1.
Ignition timing
2.
Vacuum advancer
3.
Governor controller
4.
Spark plugs
5.
Carbon build-up in the combustion chamber
Fuel
lgnition
1.
Carburetor solenoid valve
[Point
I]
2. Idle speed
1.
Spark plugs
2.
Carbon build-up in the combustion chamber
[Point
11
Inspect the carburetor solenoid valve
With the engine stopped, when the ignition key switch is turned ON
and OFF, if a clicking sound is audible from the solenoid valve, then
electrically everything is normal.
For the defective valve inspection, if there is still run on when the
throttle valve is completely closed (idling), then it can be judged that
the sealing of the valve tip is defective.
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