Flat battery, what a pain in the ass, I know what you are thinking, and it is a great question.
Top two signs a motorcycle won’t run without a battery:
- Electronic fuel injection fitted
- Lots of electrical accessories fitted
In this post, you’ll learn how to reliably check if your bike will run without the battery, you’ll also learn the possible dangers of doing so.
Kick-Start Fitted?
If your bike has a kick start fitted, there is a good chance you can run it without a battery, but wow there! that’s a generalization, we’ll need to do a little more detective work before we can answer this conclusively. And it’s worth remembering since your bike has a battery fitted, its charging system is designed to charge a battery, running without the battery therefore could damage the charging system.
No kick start fitted? If you don’t have a kickstart, there’s a good chance your bike won’t run without a healthy charged battery.
So how can you tell for sure? To do that we’ll need to check which type of fuel system you have fitted and that’s what we’ll do next.
1 Electronic Fuel Injection
A reliable way to tell if your bike will or won’t run without a battery is to know what type of fuel system your bike runs. Motorcycle fuel systems come in two flavors, carburetor or fuel injected.
Carburetors – Carburetors are fitted to all older bikes but are still in use in many modern bikes too. Higher-end larger motorcycles are less likely to run carburetors and the reasons are many, carbs are less efficient and require more maintenance than the more modern fuel-injected systems.
The carburetor is a fully mechanical gravity-fed component whose function is to mix air (oxygen) and gas together to a preset ratio and to have a sufficient quantity ready to feed the engine for any given demand.
Fuel injection – Fuel injection offers a ton of advantages over carburetors, while in some ways it’s more complicated and yet in other ways it makes life easier for both the rider, mechanic, and the manufacturer. Fuel injection allows for greater accuracy in fuel delivery and that makes for a more powerful, reliable, efficient, and cleaner running engine.
Fuel injection is a part mechanical part electrical fuel system that delivers a precisely measured amount of gas directly to the intake system.
But it’s not all gravy, while the concept of the fuel-injected engine is simple, (injects gas into the engine). It is not so simple to execute. Getting the correct amount of gas, ie the ratio of air to gas is complex, it requires sensors, a pump, actuators, and a control module (computer) known as an ECU (Engine Control Unit).
The ECU does the heavy lifting, it manages all the sensor data and makes appropriate fueling decisions in real-time for varying engine demands. And as you know none of these components will run without an electrical power supply, and as you’ve no doubt guessed, this is why most fuel-injected bikes won’t run without a battery.
The electric fuel pump is crucial to a fuel-injected system, it moves gas from the tank to the throttle body and helps pressurize the gas for delivery through the injector.
Note I have said most because this won’t be true for all bikes, some fuel-injected bikes may start and run without a battery all be it run poorly.
How do I know if I have fuel injection?
Trying to find out if your bike is fuel-injected isn’t always easy. A dirt bike engine is easy to access and identifying sensors and electrical connections on the intake system is a pretty good indication your bike is fuel injected. But road bike engines are closed in with covers and guards to help keep the weather out and not so easy to check.
Often your time is best spent on the net, googling your year, make, and model. Most good bike makes allow for engine identification and specification right on their websites with just your engine number. Otherwise, you’ll need to remove some covers to access the intake system.
Risks of running your bike without a battery
Your bike uses a stator and a rectifier/regulator to create and manage electrical current. Some systems are designed to have a battery fitted and some are designed to operate without a battery. You’ve already learned if your bike is carbureted and has a kick start you’ll likely be fine to run without a battery.
That said, it is possible to damage a stator and regulator by removing the battery, it really is manufacturer dependent.
Stator – Voltage is created as the engine cranks over and magnets positioned on the flywheel also known as the rotor, pass over the copper windings of the stator.
The stator creates A/C voltage, but a bike can’t use alternating current (A/C) and so it’s passed to the rectifier for conversation before being used by the electrical components.
Rectifier/regulator – Receives A/C current and converts it to useable direct current (D/C).
2 Electrical Kit
A second reliable way to tell your bike won’t run without a battery is the amount of electrical kit it runs. So if you have a fancy digital dashboard, twin headlights, heated grips, led lights, etc, it’s not likely she’ll run without the battery.
ECUs need power
Many latest bikes as said use engine management systems – ECU (Engine Control Unit). These guys are very sensitive to resistance as are the sensors they rely on for information. They don’t like running low on voltage, while some ECU bikes may run without a battery, they won’t be reliable.
Battery Testing
We can run two battery tests, but we’ll need a voltmeter and for the second part of this test, your battery will need to be charged. I’ve covered battery charging below also.
As you know batteries are commonly referred to as 12 volts but are actually 12.65 volts when fully charged.
The second part of the battery test is the crank test but it will require a charged battery.
The crank test loads up the battery and stress tests it. Setting your voltmeter to Min-Max will be helpful.
Battery Charging
A totally flat battery is a pain to charge, most regular chargers won’t turn on because of a fail-safe system.
Connecting a healthy battery with jumpers before connecting the charger fools it into turning on.
Remove the jumpers after 20 mins and continue cooking for 3-4 hours. Consider investing in a smart charger that can be safely left on your bike when not in use, they use minimal power and will keep the battery in great shape.
Checking Your Charging System
Connect your meter as per the picture and run the engine at approx 3000 rpm.
A reading between 13 and 14.5 volts suggests all is well.
Jumpstarting Your Bike
It is possible to jumpstart your bike from any other bike, car, tractor mower, ATV, etc. What’s important is that your batteries are both the same. Most are 12 volts (actually 12.65 volts but referred to as 12 v) and you’ll find the voltage marked on the battery casing.
Remove the jumpers in reverse order – 4, 3, 2, and 1.
You may find these posts helpful:
How do dirt bike kill switches work?
How often should I start a motorcycle?
Will dirt bike start without kill switch?
- About the Author
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John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.