Symptoms Of A Bad Motorcycle Stator


Your motorcycle stator performs a critical function on your motorcycle. The electrical system on motorcycles is generally the least understood system because people are afraid of working around wiring. Having a strong stator is important for a lot of reasons. How can you tell when it’s going bad though?

What are the symptoms of a bad motorcycle stator? The most obvious symptoms of a bad motorcycle stator include no spark, weak spark, or intermittent spark (also known as misfiring). Hard starts and a poorly running engine can also be clues that your stator needs to be rebuilt or replaced.

In this article we will dig into these symptoms and what causes them. We will also teach how you can repair your own stator and what to expect to pay if you buy a new one. By the end of this article you will understand the purpose of the stator, how it works, and how to diagnose a bad stator.

Bad Motorcycle Stator Symptoms

Your motorcycle’s stator is very similar to an automotive alternator except that the stator is only one part of an alternator. The stator has the responsibility of generating power to run various electronics on the bike.

The stator also performs the extremely important role of generating the power for the spark plugs in the engine. Without a stator, your motorcycle will not get any spark at all as your battery is not capable of supplying the appropriate power levels to generate a spark.

As a result, if your stator is going bad your motorcycle will run very poorly. Eventually, your stator can prevent your motorcycle from starting at all.

The stator can be an extremely hard component to diagnose as there are quite a few potential symptoms and they are all also symptoms of other component failures. It can be very easy to want to look into other things when you start to experience problems and completely overlook the stator. 

There are so many different signs pointing towards a failing stator. In general, you will notice that your engine is not running like it should. This could become apparent even as you start the motorcycle. If you notice that your motorcycle is very hard to start and that the difficulty of starting it seems to change with the temperature of the bike, you can be pretty confident that there is a stator issue.

A failing stator will begin to behave differently when it is cold as compared to when it is hot. This will be a great way to tell whether your stator is failing.

Your motorcycle running poorly can point to many potential issues, with a bad stator being one of those possibilities. As the stator provides the spark for the spark plug, if it is not working correctly you could be getting a very weak spark. This could be constant or completely irregular and sporadic.

You may experience occasional misfiring as you ride around. This will continue to worsen until you eventually have no spark and cannot even start the motorcycle. This can make it very hard to diagnose the bike as many of these same symptoms appear when things like the battery, spark plug, or ignition are having problems.

Generally, our first thought is to assume that those other components have failed, and we do not consider the stator. This will make it very difficult to find the actual problem.

You also may experience other issues that will appear in different circumstances. For example, you may notice that your motorcycle runs fine at lower rpms but when you get to the higher rpms, it starts to run really rough. This is a result of the high-speed coil in the stator going bad. The opposite can also happen with the low-speed coil. These will be signs that your stator is failing.

You may also notice that your bike will start back-firing. This could be a result of a bad stator. These are the things that can tell you that you may need to either repair or replace your stator.

What Causes A Stator To Fail?

Stators can fail for multiple reasons. The first and generally most overlooked cause is time. Everything wears out over time. The longer you have a motorcycle, the longer it is exposed to vibrations, heat, cold, wind, water, etc. All of these things will wear on all your motorcycle components.

Your stator will wear out over time. Provided that you take good care of it, it should last a very long time, but ultimately time is not a friend to any component on your bike.

The other main cause for your stator failing on you is a power overload. This can happen when you run too many accessories at the same time. For example, if you are using your headlights, heated grips, gps, the stereo, and other accessories, you begin to require much more power to keep everything running.

Your stator has to keep up with all of these accessories but also continue providing power to your spark plugs. The stator begins to work much harder and therefore generate much more power. Over time this can wear out your stator. You can actually burn the stator and rectifier by overloading it. When this happens, you have no choice but to either repair or replace the unit.

Can You Repair A Stator?

Let’s assume that your stator has just burned itself up. Can you repair the stator yourself? Or is it best to go take it to a repair shop? You actually can repair the stator. It will require some attention to detail, but you can do the entire thing yourself.

Stators can be very expensive to replace entirely. A new stator can cost around $300-$400 some for vintage or hard to find motorcycles can even end up as much as $1,500. That is just for the part itself. You can save yourself quite a bit of money by repairing the stator.

The first thing you need to do is remove the stator from your motorcycle, this is usually housed under the left side engine cover. Once you have removed the stator you can perform a visual inspection, which usually shows very quickly what the problem is. Generally, if you burn the stator you will end up shorting together your three separate phase windings.

Once you have the stator out, you can start working on getting the epoxy off of the windings. This will let you actually get to the windings and remove them. This part can be very tricky as the epoxy is pretty hard to remove. Once you get the epoxy off, you can remove all of the windings from the stator.

Now, you can prepare the stator to be re-wound. You will want to file off any sharp edges on the stator. Now you are ready to get the stator re-wound. You will need to buy new AWG wire. Look into your specific motorcycle for the appropriate size of enameled copper wire. The winding can be very tricky as you must wind three separate phases. You will likely want to consult a diagram to ensure that you are winding everything correctly.

Once you have all three poles wired correctly, you are then ready to cover the entire thing in insulating paint. This will help the stator to last a long time again. After coating the stator, you will want to cure it in an oven at 300 degrees for about 30 minutes. Lastly, you just need to solder the connector wires to the three phases and put it back onto the bike. It should run like new again.

How To Make Your Stator Last As Long As Possible

Your stator will last quite a long time if you take proper care of it. Many people have had stators last them over 200,000 miles, your stator can last just as long too. The main reason that stators get burned is from high amperage. If you need higher amps, it will shorten the life of your stator.

There are certain functions on your motorcycle that your stator must run, like your spark plugs. This amperage is absolute and cannot be decreased. Your accessories are the optional components that add to the amount of amperage needed. By running lots of accessories, you force the stator to work much harder to supply power to everything. Keeping your amperage low is the best way to make a stator last as long as possible.

Vibration also does a lot of damage to your stator. Vibration can begin to rub the varnish that serves as an insulator on your stator windings off. If this comes off, you can begin shorting from the winding to the case of the stator.

Shorts also ruin your stator pretty quickly. This is a much harder thing to prevent though. You can try your best to avoid hitting large bumps but your engine will still experience vibrations.

Recent Posts