Flat battery, what a pain in the ass, I know what your thinking, and it is a great question.
Top 2 signs a motorcycle won’t start without a battery:
- No kick-start fitted
- Lots of electrical accessories fitted
In this post you’ll learn how most bike ignition systems work and why you shouldn’t run your bike without the battery.
No Kick-Start Fitted
Yes, some bikes will start without a battery and some just won’t. Generally speaking, if your bike has a kick start, you can likely start it without a battery. No kick start, then it probably won’t start without a charged battery.
But you should know, running a bike with the battery disconnected, will fry the charging system. And it gets worse, as the charging system also supplies the power to keep the coil and spark plug firing, your bike may stop running.
Running without a battery will risk damaging the stator, regulator/rectifier and the CDI box all expensive components.
If your bike runs a ton of electrical stuff, fancy digital dash boards, twin headlights, heated grips, led lights etc, its not likely she’ll run without the battery.
And if she did, using any of the electrical accessories would rob the engine of the voltage, and the engine would stall.
Lots of recent bikes use engine management systems (computers) that means they are very reliant on voltage stability. Remove the battery on this bike and the bill could be very expensive.
No matter what bike you ride, they all require voltage to run their ignition systems.
So if there’s no battery fitted, where does the power come from? Voltage is created as the engine cranks over and magnets positioned on the flywheel, pass over the copper winding’s of the stator.
The CDI (Capacitor Discharge Ignition) box receives the voltage from the stator and also a pulse from the crankshaft position sensor (aka pickup coil, pulsar, trigger coil) which indicates the correct time to fire the plug.
The CDI processes the pulse and sends a voltage to the primary winding’s of the coil which passes to the secondary winding’s and produces in the region 30k volts needed to fire the spark plug.