Will Dirt Bike Start Without Kill switch? (Yes, here’s why)


Ever wondered what’s the point of a dirt bike kill switch and an ignition switch, do we really need both.

A dirt bike will start if the kill switch is disconnected. Your dirt bike kill switch serves an important function, it’s an emergency off button, and it must be fitted by law.

In this post you’ll learn why a dirt bike will start when the kill switch is disconnected, and you’ll also learn the important function they serve.

What’s The Point Of A Kill Switch

The kill switch is a safety feature that’s fitted to all bikes. It serves as an emergency shut off button and that’s why they are always easily accessible and coloured red.

In the event of an accident, emergency services are trained to use the kill switch (aka e-Stop) or another road user could easily identify and operate the red kill switch button on the handle bars.

The button is designed to be used by the rider without removing a hand from the handlebars. Turning the ignition key off (most bikes) would do the same job, but the key is fiddly and can’t be as easily located or operated.

Consider experiencing a stuck wide open throttle, while wearing riding gloves and fiddling with an ignition key, isn’t practical.

Kill Switch Function

Kill switch wiring differs from bike to bike, but the net result is the same – hitting the kill switch turns off the engine.

The ignition will still be on and if the key isn’t turned off also, the battery will drain.

Using the kill switch to shut your bike down as part of your normal shut off procedure is perfectly OK. It’s a misconception by many riders that doing so long term will damage the battery or wiring, it won’t.

Not so, as in most cases the kill switch and ignition switch are wired in parallel, meaning they are doing the same job.

Many bike handbooks state you should only use the kill switch in emergency or electrical damage may occur. They are being diplomatic here, they are alluding to a couple of common human error situations:

  1. Forgetting to turn ignition off after hitting the kill switch causes the battery to run down.
  2. Forgetting to turn the kill switch back on when restarting, causes the rider to crank and crank, potentially running down the battery, cooking the starter motor and flooding the engine with gas.

How Does It Work

The kill switch is a very simple on/off switch. When activated it opens a ground path to the CDI box, shorting it out and shutting down the coil.

The coil as you know makes the voltage for the spark plug, no spark equals no fun.

Your ignition system consists of a few critical components, a typical start procedure looks like this:

  • Ignition switch “On” – Initiates system, by removing the ground path to the CDI box, and sending power to the start button.
  • Kill switch “RUN” – removes the secondary ground path to the CDI box
  • Clutch/Neutral switch activated – Offers a ground path to the starter solenoid.
  • Start button pressed – Power flows to the starter solenoid which connects battery power direct to starter motor and cranks the engine.
  • Stator – creates voltage and powers the CDI box as the engine cranks.
  • Trigger – creates a voltage, used by CDI box to identify the correct time to fire the plug (timing).
  • CDI box – processes the trigger signals using Capacitor, Diodes and an SCR, the timed voltage is sent to the coil.
  • Coil – produces high voltage through primary and secondary winding’s which is converted to a spark inside the combustion chamber by the spark plug.

So could you delete the Kill switch?

Yes you could, but it isn’t advised. To delete the kill switch simply disconnect the wire.

Points to note:

  • It’s is mandatory to have a kill switch fitted to a motorcycle, for road use and parks and recreation areas may not permit motorcycles without an operating kill switch.
  • Insurance companies may void insurance cover and reject claims if a kill switch is deleted.
  • In the event of an accident, injury caused by a deleted could result in a prosecution.

John Cunningham

John Cunningham is an certified mechanic and writer on ATVFixed.com. I’ve been a mechanic for over twenty years, I use my knowledge and experience to write articles that help fellow gear-heads with all aspects of ATV ownership, from maintenance, repair to troubleshooting.

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