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Owning a motorcycle can sometimes feel like you're missing an engineering degree. Terms like alternator, stator, and rectifier can sound like technical gibberish to the uninitiated.
An alternator is simply the thing used to generate electricity in the bike, which is needed to power the headlights, indicators, and the engine itself. So, what's the deal with motorcycles and alternators?
We've put together a layman's guide to answer any burning questions you might have about alternators, in plain language that anyone can understand. You might already know what an alternator is, but we'll go through exactly how it works so you have a total understanding of exactly what's powering your motorcycle.
Yes, most motorcycles have alternators that charge the electrical components while they're operating. However, the alternators found in bikes work a bit differently from the ones found in cars, due to their substantial size difference.
The electrical system in bikes is usually powered by a type of alternator called a stator. Stators are much smaller and less complex than standard car alternators, which is why they're commonly used for motorcycles.
Whether you're a technical whiz or not, knowing about the different types of power sources is an important part of owning a motorcycle. So keep reading and we'll take a deeper look into alternators, stators, and their main differences.
So we've established that an alternator powers the bike with electricity, but what exactly is it? How does it actually work? Don't worry, we won't get too fancy on you.
This section will establish what an alternator actually does, the main differences between alternators and stators, and how to locate the alternator on your motorcycle.
First of all, the word 'alternator' is kind of an umbrella term that describes how a vehicle produces its power. Most bikes use stators, which are just simpler and smaller alternators, and the two words can often be used interchangeably.
Simply put, an alternator is a mechanism that converts mechanical energy into electrical energy. Most vehicles have one in some form or another.
A bike can't run off a battery alone, or it would drain extremely quickly and leave you stranded. The stator is what keeps the battery continuously running.
Once a bike is turned on, the kinetic energy (or motion) from the motorcycle engine crankshaft prompts the stator to start working.
When the bike is running, the stator starts rotating and generates an electrical current back to the battery and the ignition system, restoring the battery's charge. So the stator constantly feeds energy into the battery, ensuring it doesn't go flat.
Whether it's on a car or a motorcycle, the alternator does the exact same thing: keeps the battery charged and powers the bike with electricity. The only major difference between the two types is in their construction.
Cars are obviously much bigger than bikes and so are their alternators. A car's alternator is a big, bulky thing that you'll find under the hood near the engine.
Unlike with bikes, it's an independent, externally mounted unit that's entirely separate from the engine. So if it needs to be serviced, you can just take it out and work on it. There's no need to open up the engine assembly like you would for a motorcycle.
A car alternator has three parts: a stator, a rotor, and a unit that contains the rectifier and regulator. So even though we call it a stator in a motorcycle and an alternator in a car, they share many of the same parts.
When it comes to motorcycles, the stator is normally considered to be a part of the engine. It shares pretty much the same parts as a car alternator, but things are laid out a bit differently.
A bike stator is connected to the engine crankshaft, and the unit that contains the rectifier and regulator is found at a different location.
Getting to a motorcycle stator means opening up the engine assembly since a bike's stator is part of the engine. Stators are important parts of motorcycles that are usually very reliable, but they'll occasionally need some maintenance and inspection just like any other part of the bike.
The alternator or stator of a motorcycle is usually mounted on the left side of your engine crankshaft. It should be on the side opposite the carburetor or air intake.
The exact location might change depending on the make and model of the motorcycle. Some common places to look are the side or bottom of the engine case, the rear of the engine, or near the gearbox. Consulting the bike manual is a good first step toward finding the stator.
Remember that alternators on motorcycles are part of the engine, so if you want to do some work on it that means taking apart the engine assembly. The alternator won't just be conveniently sitting there like it would in a car.
The alternating system of vehicles is a fairly straightforward mechanism, but motorcycles adopt a slightly different system for their electrical power. This raises the obvious question; if it's such a simple process then why use different systems?
Well, it's all about size. If you've never seen an alternator in a car then look up a picture. They're huge! A motorcycle simply can't accommodate something that bulky.
Since bikes are way less complicated than cars, it means they can use simpler technology as well. Stators require less complex parts and they're way smaller, which is why they're commonly used in motorcycles.
Back in the day, before stators were a thing, bikes used something called a magneto instead. No, not the bad guy from x-men. This was a very basic alternator that did the exact same thing as a stator, only much more primitive.
As the technology of alternators improved over time, stators became the go-to mechanism in almost every motorcycle made today. They're a middle-ground between the basic magnetos and the more complex alternators used in cars.
Every vehicle has some kind of alternator charging system to provide electricity and to get it started up. They all function in a similar way no matter the vehicle, but with a few key differences.
An alternator in a car or motorcycle functionally does exactly the same thing. They share most of the same parts, including a stator, and both handle their power generation task with similar components.
The biggest difference between the two types of alternators is how it's all put together. Alternators in cars have everything placed together in one big, bulky component. A bike stator, on the other hand, has its parts dispersed throughout the motorcycle.
Another key difference is how the electromagnetic induction system works. In vehicles like cars, an alternator gets its rotating mechanism indirectly from the engine. This usually involves a series of chains or belts that connect the engine to the alternator.
In motorcycles, the stator gets generated with a direct current from the engine, since it's located in the engine itself.
So if the stator is generating power, what's the point of a motorcycle battery? Well, a motorcycle's battery can't function without the stator, and the stator can't function without the battery.
The battery power is what gets the motorcycle started. The stator doesn't start working until the bike is turned on, and the bike can only turn on once it gets some electrical power from the battery.
A bike's battery is pretty much there to turn the bike on. Once it does that, the stator does all the rest. But every time you start the bike, it drains a little bit of power from the battery. The stator is what restores power to the battery, so it's charged up and ready to start the bike again the next time you ride it.
As a motorcycle owner, it's important to be able to recognise tell-tale signs of an issue with the stator. If you own a bike for long enough, a problem with the stator will probably come up sooner or later.
The most obvious sign of alternator problems is when the battery doesn't seem to hold a charge. You might notice the bike seems a bit sluggish, and the lights seem to dim quicker and quicker. If it gets really bad, the bike might even start to slowly die out while you're on a ride.
As mentioned above, a battery can't operate without a stator. Without the stator feeding it power, the battery can't take the load of your motorcycle by itself. This is why stator issues will prevent you from getting to or staying in high RPMs. If the engine dies when you suddenly accelerate or rev the engine, this indicates a problem with the stator.
Another sign of a stator problem is a kind of 'whirring' sound coming from one side of the engine. If you start to hear it, it means the magnetism in the stator isn't working.
You can inspect the stator itself if you believe it may be faulty. The bike manual should tell you exactly where to find it, or refer above to the section on finding the stator. Check the stator for things like burn marks, melted components, or frayed copper wires.
Better yet, if you have a multimeter handy it will save you the trouble of opening the bike up. This nifty device lets you test how much voltage a stator is emitting. You just need to find the stator connector and perform an AC test while the bike is running. Check the voltage read on each terminal. If one read differently from the other, there's a problem with the stator.
We've already covered everything you'll need to know about motorcycle stators, but here's some extra info for those interested in taking an even deeper dive.
So motorcycles do have alternators, just not the same bulky ones that are typically found in cars. They're built a bit differently, but all the same, parts are there and it performs pretty much the exact same function. Motorcycle stators are a lot smaller, but a necessary part of starting and running the bike.
While topics like these can get very technical, it's important to know your way around a motorcycle if you plan on owning one long-term. Issues like these come up very rarely, but you'll be glad to have the knowledge when they do.