Spark plug can't provide a spark for a variety of reasons. A spark plug is the last device of the whole ignition system. Any issue in the whole ignition system can cause the spark missing in the spark plug. This situation needs one to check any fault in the ignition system diagram.
Before you can check the ignition system you need to know the whole ignition schematic to be an expert on the ignition process. Let's see what is ignition and how it works.
What does the ignition system consist of?
The ignition system consists of several conductors and semiconductor devices. These are a static power source i.e a battery, an inverter circuit, a capacitor and an ignition coil. Direct current from a battery is supplied to an inverter circuit that consists of one or more transistors. This is how the direct current (DC) is inverted to alternating current (AC). We need ac because only AC can be stepped up through magnetic induction by ignition coils. A diode and an SCR are used across the output of the inverter.
Before the current is supplied to the ignition coil a Capacitor is used in series in the CDI ignition system. The capacitor stores some energy for a very small period of time. This way first the capacitor is charged, and then it is discharged by charging the ignition coil. Then it again gets charged from the powers source. This is how the ignition coil is charged. The ignition coil at the same time steps up the voltage of the current to as much as 40KV. A high voltage is achieved because it's necessary for spark fire.
A spark plug is used next to the ignition coil as the oven for the fire.
Fault that is causing no spark in pit bike.
Low voltage in the battery
If the battery is not charged properly it will lose voltage over time. So if a 12V battery goes down to 8 volts it will less likely work.
The inverter circuit is a combination of some BJT and MOSFET transistors. It works very fast to change the direction of the current and so it becomes too hot. Without proper hit dissipation, it can burn out.
Transistor or diode failure
Transistor or any burnt diode can block current to pass to Ignition coil for what spark plug won’t get any power.
Power on a CDI Ignition system passes from the inverter to the ignition coil through a capacitor. So if the capacitor is burnt it becomes an open circuit and no current passes.
Ignition coil burnt
Ignition coils are rare to burn out as the main source is a steady direct current (DC). Still, after a long time, the core of the coil can lose the insulating burnish and cause a short circuit. So you can measure this with a meter.
Spark lid burnt
The spark lid in the spark plug is often burnt out over time. It's normal to occur. It's a usual decay. In this situation, you have to replace the spark plug with a new one.
As the incident of Spark plug damage is very common, many want to repair it. It also seems like it’s easy to repair. Because it often happens so, that the spark lid gets burnt. So People ask the question if they can solder a silver or copper lid to the place. It's technically ok to solder one there. But the problem is every spark plug has a parameter that specifies the accurate distance between the positive lid and negative lid.
So if keep more distance than it should be, you won’t get a spark. On the other hand, if you set the lid closer than it should be it will draw excessive current resulting in the burning of the ignition secondary coil. This way also you will get a poor spark. Because too close lid has little space to make sparkline. So it’s not recommended to rewire the spark lid.
Besides, you won’t get that heat sustainable lid since the spark of 40KV current makes a huge hit.
How can you find the fault?
Not all faults can be detected by yourself. Some crucial issue has to be fixed by motor garage expert. But a few things that you can test are my focus now. Here , If you spart plug not work, pit does not start.
You can check if all the wire from the battery to the ignition coil is connected tightly. For this, you don't need to understand the diagram. You just check if any connector is open or loose in connection.
You can use a small multimeter to test if the battery is providing the rated voltage that it should provide. The rated voltage is labeled on the battery. Select DC Voltage in the Voltmeter. Connect the red wire of the voltmeter to the red terminal of the battery and the black wire to the black terminal. You can see the battery voltage on the multimeter.
If the meter reading is more than 2 volts less than the voltage rating then the battery is highly discharged and needs attention. You can dismantle the battery from the bike and use an external charger to charge your battery. The external battery charger's voltage rating can be at most 2 volts higher than the battery voltage rating. But the current rating of the charger is any number above the battery current rating.
Ignition coil Test
You can also test the Ignition coil if you can reach this. Safely disconnect the battery connection. Discharge the capacitor with a screwdriver. Short the two terminals of the capacitor with the screwdriver. It may make a big spark sound. But don't worry; the sound won't last longer than a second. Then you can use the multimeter to test the primary coil of the ignition coil. Remember, the coil that received the wire from the battery and inverter side is a primary coil. This time set the multimeter to Ohm selector. Now connect the multimeter wire with two wires of the primary coil. If the coil is shorted the meter will show less than 100 ohms. If the coil is burnt or open, the meter will show more than 10 Mega ohms. Both readings provide fault repot.
However, You can check the spark plug by yourself.
The ignition coil produces high voltage. So handle with care. Don't touch the ignition coil or spark plug without disconnecting the battery connection.
Last Updated on June 28, 2022 by fahad