Why Do Motorcycles Have A Kill Switch? – (Engineer’s Guide)

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You must have noticed too many switches on the handlebar of your motorcycle, which serve various purposes. A big red button near the handlebar is called the kill switch. All modern motorcycles have this button.

So, why do motorcycles have a kill switch? A motorcycle has a kill switch on the handlebar because it lets you turn off the engine in an emergency without taking off the hands from the handlebar. Turning off the engine with a kill switch is more convenient than taking your hands off to rotate the ignition key.

Motorcycle Kill Switch

What’s The Purpose Of Kill Switch in Motorcycles?

The primary purpose of the kill switches on motorcycles is to cut off the current supply of the ignition coil in an emergency to stop the engine.

When riding at high speed, taking your hand off the handlebar and rotating the ignition key to turn off the engine is risky.

Sometimes, the ignition key gets stuck when a motorcycle encounters an accident, so it becomes tough to shut off the engine.

So, the motorcycle manufacturer installed a kill switch button near the right side of the handlebar. This switch helps to stop the engine immediately in an emergency.

Another exciting purpose of the kill switch is that people often feel lazy to switch off the engine with the ignition key on the traffic signal.

So, the kill switch becomes a great feature to turn off the engine on a traffic signal. This will prevent unnecessary fuel consumption and improve your motorcycle’s fuel economy.

How Does Motorcycle Kill Switch Work?

The kill switch sends the signal to the CDI (capacitor discharge ignition) unit, which cut-off the current supply of the ignition coil, and the engine stops.

If you have an old motorcycle, the kill switch stops the electric supply to the spark plug/ignition coil, and in modern bikes, it cuts off the fuel injector’s current supply.

Once your ignition coil doesn’t receive electric current, it won’t create a spark in the engine cylinder. As a result, the compressed air-fuel mixture in the engine cylinder won’t catch fire, and your motorcycle won’t generate power.

Kill Switch Wiring Diagram

Does Using a Kill Switch Harm The Motorcycle?

Using a kill switch to stop the motorcycle is completely safe, but don’t use it regularly. Because the switch is made from plastic, it slowly became loose due to wear and tear. So, once the kill switch is damaged, your bike will face problems in starting.

Also, the kill switch doesn’t cut off the main supply, so other accessories, like lights, ABS modules, ECU, instrument cluster, etc., will drain the battery if you leave the ignition key turned on.

So, don’t just turn off the kill switch when parking your motorcycle. Instead, rotate the ignition key to turn off the main current supply to save the battery charge.

Can a Motorcycle Start Without Kill Switch?

Most heavy motorcycles with powerful engines have a kill switch button for emergencies. However, some motorcyclists don’t like the big red button on the handlebar. So, they can replace it with a small one or remove it from the handlebar.

But, in that case, you need to short the red and black wires of the switch so that it won’t interrupt the current flow to the ignition coil. You can start the motorcycle by shorting the kill switch wire. But, for that, you should know the CDI wiring diagram.

How To Start a Motorcycle if Kill Switch is Broken?

If you frequently use the kill switch button to stop the engine, the plastic button will break or lose because of wear and tear. In that case, you may face problems in starting the motorcycle engine.

So, how to start a motorcycle if the kill switch is broken? If you’re outdoors and the kill switch breaks, take a screwdriver from the toolbox and open the kill switch from the handlebar. Disconnect the positive terminal of your motorcycle battery, inspect the wiring, and connect the (short) red and black wire of the kill switch button.

After shorting the kill switch wires, an electric current will flow to the ignition coil, and your motorcycle will start. Once you reach home, you can replace the kill switch button with a new one.

How To Repair a Broken Kill Switch?

Motorcycle Kill Switch Replacement

A broken kill switch will create problems in starting your motorcycle. Although you can short the red and black wires of the kill switch to start the engine, it’s just a temporary solution. If your kill switch is broken, you can replace it yourself.

Here is how to replace a broken kill switch button on a motorcycle:

  • Buy a kill switch button for your motorcycle model.
  • Disconnect the positive terminal of your motorcycle battery.
  • Remove the kill switch button with the help of a screwdriver.
  • Disassemble the switch and click a photo of the wiring diagram.
  • Now, replace the new kill switch button that you purchased.
  • Connect the wires correctly (take help from the photo).
  • After installing it on your handlebar, connect the battery’s positive terminal.

That’s it! You have successfully replaced the broken kill switch. Rotate the ignition key and press the starter switch to start the motorcycle.


The kill switch is an emergency button to stop the engine quickly. The kill switch cuts off the current supply of the ignition coil, and your bike engine stops even when other electrical accessories are functioning.

There is no harm in using a kill switch, but it’s not recommended when parking the motorcycle somewhere because it won’t shut off the main current supply as the ignition key does.

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