9. Ignition System
Troubleshooting
Engine cannot be started.
Check fuel and air channels for any faults; If the fuel and air channels are normal, check the
ignition system.
Inspect ignition system for the following items:
1. Spark inspection:
Check in the following steps:
Remove spark plug
Remove spark plug cap
Set high tension flexible cable end to earth
Check spark arc
It is normal if spark arc is more than 8mm，while it is weak if it is less than 5 mm.
If the spark is normal, check the spark plug.
A faulty spark plug may be caused by the following reasons:
(1) Spark plug is too wet and drowned. This is because the gas mixture is too thick. Cut the
fuel and start the engine several times..
(2) Carbon deposit on spark plug---Mixture too thick or oil combustion in the combustion
chamber. Clean and burnish the spark plug.
(3) Cracks with spark plug insulator.
(4) Spark plug electrodes have short circuit or it is obstructed between negative pole and
thread or positive pole and input end.
2. Faulty spark includes: no spark and weak spark.
Inspect the following aspects if there is no spark.
(1). Inspect ignition coil with multimeter or measurement in the following steps:
1) Measure primary bobbin resistance, usually it is about 1.
2) Measure secondary bobbin resistance, usually it is about 4.2K.
3) Measure damp resistance, usually it is about 5K.
(2). Check CDI if it is out of service.
(3). Check ignition circuit. Usually the voltage between black wire and earth wire (green)
should be 12V. If there is no voltage, check from the battery positive terminal to the end of black
wire.
(4). Check the cable: check if there are any faults from the input of trigger signal (output of
magneto pickup) to output (CDI terminal) and ignition output wire (black/yellow).
(5). Check stop switch. When switch is at the ignition position, black/white wire should be cut
with green wire.
In case of weak spark, check the following:
(1). Check CDI .
(2). Check ignition coil and secondary coil whether there is short circuit, or fault with the damp
resistance.
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