When to Change Motorcycle Spark Plugs?

Motorcycle riders hardly remember to notice their rides’ spark plugs. Because it’s hidden and should be fine right?

That’s what people usually think. Tires, brakes, and stuff on the outside are checked regularly, usually before every ride. But spark plugs aren’t lucky and don’t get checked as much.

If you’re just looking for an answer of when to change motorcycle spark plugs, then it is about 15000/16000 miles. It’s a generic answer and applies to new bikes or bikes that are used for basic rides. Commuting and using the bike to give short trips here and there falls into the basic rides’ category.

But if your riding habit differs from this, then the rules won’t be the same for you too. There are no fixed rules; however, you should keep in mind some factors.

And we’re going to talk about those factors as well as some guide to keeping a motorcycle’s spark plug in the best shape. So, it’ll require less maintenance.

With that in mind, let’s start discussing the important bits of a spark plug’s checking and maintenance.

Checking Spark Plug

There are two electrode points in a spark plug. Notice where the spark gets made. There are two points, right? Those two are electrode points.

Since they create combustion all the time, the colors for both of them are kind of like a brownish tint. That’s the normal color. If you see this, it means they’re in good condition.

Now, a spark plug shouldn’t come into contact with liquid fuel. If that happens, the consequences can be dangerous. It might lead the engine into fire bursts. But why does a spark plug get wet? The likely reason behind this is fuel leakage. 

If fuel leaks from the engine and falls into the electrodes, the points will get a thick brown tint. And if fuel and air mixture is out of balance and fuel has the most percentage in the mixture, the resulting plug color will be dark black. 

Now, if you notice any of the issues mentioned above, you should see a mechanic as soon as possible. Using a faulty spark plug or a leaking valve/fuel chamber may become a disaster.

Also, notice the plug for breakage in its body as well as in its electrode points. When a spark plug gets old, these signs will start to show.

There is only one solution for these issues: replace the plug. It’s not expensive, nor is it time-consuming. In fact, it’s quite easy as well. You have no reason not to change it.

When you notice excess blacking in the electrode points, it’s a sign that there could be some damage to the carburetor. The spark plugs start to get more carbon on their electrode points when a carburetor can’t maintain the air and fuel mixture. These are some well-known signs that you can easily check for on your own.

How to Change a Spark Plug on Your Own?

You should never have to depend on a mechanic for a simple task like changing the spark plug of your motorcycle. Here’s how to do it step by step.

Step 1

Remove the plug wiring from the plug itself. The wiring works as a connection between the plug and the engine coil. Pull the wire, and it’ll come out. There’s no complicated process here in this step.

Step 2

Use a spark plug socket to take the plug out. Check its coloring to see its current state. This will give you some ideas on what could be the underlying reasons for your spark plug damage

Step 3

Take a new plug that’s of a similar size as the previous ones and set it inside the engine. Connect the wiring, and you’re done. That’s how simple it is to change a spark plug. 

But remember, don’t over-torque the plug. It’s a sensitive component, and if you try messing with it too much, it might get bent out of shape if the threading on it gets removed.

Use a good torque to set it up or measure the torque by your guess. Going extreme in any direction while tightening it can create engine faults.

What are the Signs of a Bad Spark Plug

Some signs you can notice when your spark plug goes bad are – 

Imbalance of Air Fuel Mixture

When the amount of fuel in the air-fuel mixture is high, the consistency is known to be lean. And when there’s more air around a spark, the fire is hotter and larger in size. That’s what happens in the combustion chamber.

If a spark plug faces high heat on a regular basis, it has a hard time adjusting to it and starts to melt its plug points down. Slowly, the length between the electrode points starts to increase, and as a result, the plug fails to create sparks in time.

Conversely, when the fuel amount is high in the mixture, but the air is not enough to create combustion, it results in a faulty spark plug.

Even if the engine and other components are doing well, the flooding inside the engine makes the spark plug unusable. See a mechanic to adjust the plug positioning. 


When a spark plug misses its firing a few times at a stretch, what happens is that the combustion can’t happen inside the engine. The fuel mixture is created and immediately gets pushed out through the combustion pipe. And while the mixtures leave out of the engine, that’s when it catches fire in the tailpipe. 

In fact, you may notice liquid fuel coming out of the tailpipe sometimes. That happens for the same reason but with the difference that it doesn’t create combustion. The fuel gets left out in the same form it was inside the engine.


A spark plug fires in accordance with the gas input in the engine. If there’s a slight imbalance between the timing of the gas-air mixtures and the plug firing, the difference in combustion can easily be felt. 

How to notice it easily? Just look for the engine sound. Notice an imbalance of combustion timing. In normal circumstances, the sounds will be steady. When there’s combustion, the sound is easily differentiable.

Engine Overheating

If you need to check your engine to see how hot it’s gotten every once in a while, in between a ride, then maybe it’s a sign of a bad spark plug.

Why? Because when a spark plug works well, it maintains the timing of the ignition, so the engine doesn’t need to get much heat, the combustion chamber quickly transfers it away.

But when there’s a fault in the timing, the combustion gets inside the engine and can’t leave from there quickly. As a result, it gets hot and needs some break if it runs for too long. If the plug’s condition is well, the engine hardly has to take breaks like these.

Does Changing Spark Plugs Make a Difference on a Motorcycle?

Changing the spark plugs on a motorcycle can make a noticeable difference in how the motorcycle runs. This is because the spark plugs are responsible for providing ignition power to the engine.

When they are old or dirty, they can cause the engine to run poorly. By replacing the spark plugs, you can often improve the performance and fuel economy of the motorcycle.

Final Words

Although changing a spark plug isn’t complicated, knowing when to do it takes some regular checking and brainwork. You now know when to change motorcycle spark plugs after going through this guide. If you can ensure regular maintenance and immediate action, you can keep your engine in the best shape.

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