Do Motorcycles Have Alternators?



Typically, batteries power the various electrical functions of cars and trucks. This includes starting up the engine, turning on the headlights and taillights, controlling brakes, turning on blinkers, and so on. During the times when the battery needs to be charged, the alternator saves the day and comes into play.

However, does this apply to motorcycles as well? Do motorcycles have an alternator, and if so, how does it charge the battery?

The short answer to that question is Yes, most motorcycles do have alternators

In this article, we discuss exactly that and more. We’ll talk about the difference between a car’s alternator and a motorcycle’s, as well as the telltale signs to know if your alternator needs replacing. 

What Is A Motorcycle Alternator?

An alternator is a device designed to produce alternating current (AC).

It converts mechanical energy produced by the rotary motion of an engine crankshaft into electrical energy to power your bike. 

The alternator is often mounted on the left or right side of your motorcycle’s crankshaft. These components are often considered part of the engine.

How Does The Charging System Of A Motorcycle Work?

There are generally three key factors in generating electricity and charging the battery of a bike. These are the engine’s motion, magnetism, and field coil. 

Power is generated when the engine rotates, causing the flywheel’s magnet to spin around the alternator’s magnets and thus generating a current using the coil of a wire. The current is then supplied to the battery to maintain its voltage. Once the motorcycle is started, it recharges itself via this mechanism. 

Motorbikes also require direct current (DC) to power their electrical systems. Since motorcycle alternators only produce AC, they require a rectifier to convert it into DC. Through it, the DC is regulated to provide just the right amount of voltage to the battery, completing the process. 

Why Do I Need A Battery If I Have An Alternator?

Most modern motorcycles lack a kick-starter function and rely on the battery to provide electricity to start the bike. The battery supplies power to the spark plugs, creating a charge that causes the engine to start. After that, electricity is generated by the alternator.

Also, since the alternator only works when the motorcycle is running, sometimes you may need to turn off the engine and still require electricity to operate certain functions.

For example, during traffic stops, the blinkers should still be kept on, and your motorcycle horn should still work even when the bike’s engine has been shut down. This is where the motorcycle battery comes into play. The alternator and the battery work together to provide power in all scenarios.

Do All Motorcycles Have Alternators?          

If your motorcycle is from the newer generation, then it will most likely have an alternator. An older model may not have an alternator, but a low-power alternative like a DC generator or a magneto instead. 

Difference Between Motorcycle And Car Alternators

The alternator for all types of vehicles may have the same function, which is to produce alternating current, but the way they are constructed can vary. 

One-piece alternators are commonly used in cars. They come in a single self-contained unit equipped with all the components needed to regulate and generate electricity. These are automatic and are typically installed on the outside of the engine since they generate a lot of heat. They produce DC current, use electro-magnets, and can be serviced without opening the engine assembly. These types of alternators can also be found on some large touring bikes. 

On the other hand, you may find it a bit more difficult to find the alternator on your bike the first time as it is not usually a separate component of the engine but a part of the engine assembly.

The most common alternator on a motorcycle is called a “stator”. It comes with three parts, namely, the rotor, the rectifier, and a regulator unit. Although they work together, these three parts can be serviced separately. Also, unlike cars, the alternators on motorcycles use permanent magnets.

Signs Of A Faulty Alternator

The battery of a motorcycle has a limited capacity to keep it running, so if it is not recharged, the bike will stop working. Therefore, if your alternator fails, the battery will die.

An alternator that is not working properly won’t allow you to reach high RPMs and will make it difficult to maintain a consistent speed. A faulty alternator won’t be able to transform the direct current to an alternating one consistently, meaning your engine will run erratically. (Read about when to shift gears.)

You will also notice unusual whirring sounds coming from the engine when the alternator becomes defective. This is usually caused by a failure of the alternator’s magnetic component. Some other signs of a faulty alternator include:

  • The battery quickly loses its charge or doesn’t get recharged.
  • The headlight dims down.
  • The motorbike becomes sluggish.

Testing A Motorcycle Alternator

To confirm that your alternator has issues, here are some things you can do:

Manual Inspection

This first method is the easiest. Simply start the engine, turn on the headlight, and start accelerating. It is possible to identify a working alternator if the light gets brighter as you accelerate.

Voltage Test

You can also use a multimeter to test the voltage of the stator. First, locate the stator’s connector and do an AC test. Next, check the voltage of your battery while the engine is off. Once you have completed this measurement, start the engine to test the voltage again. Take note that the voltage will be slightly higher when the engine is in use as the generator provides an additional charge to the battery.  

If your generator or alternator is operating as intended, your reading should rise to approximately 14 volts. Also, the voltage readings on each terminal should match each other. If you see one reading differently, it is likely that the stator is defective. Read more about bad stator symptoms.

Visual Inspection

Visually check the condition of the alternator. Look for the exact location of the alternator using the owner’s manual. You can remove one of the side covers of the engine and inspect the condition of the alternator. Are there any burn marks, worn-out copper wiring, or melted components? If so, your alternator needs fixing.


Yes, motorcycles do have alternators that power your bike’s headlights, brakes, and other electrical functions. Your motorcycle’s alternator is an important component, and just like all other parts, it requires regular maintenance. Even if your bike is an older model, it’s worth checking the electrical system and planning for any repairs or upgrades.