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Bad Spark Plug Symptoms In A Motorcycle Discussed With Replacement Tips

Bad Spark Plug Symptoms Motorcycle

Signs Your Motorcycle Spark Plugs Have Gone Bad

Like a car, the motorcycle’s spark plug is also a critical component to look after on a regular basis. Spark plugs can get worn out, too, for many causes. And when such an essential part of the vehicle wears out, you will get some symptoms before the plugs completely die.

Bad Spark Plug Symptoms Motorcycle

In this article, we are going to talk about the major symptoms of bad spark plugs on a motorcycle so that you don’t overlook those.

4 Bad Spark Plug Symptoms in A Motorcycle

1. Flooded engine:

Flooded motorcycle Engine

Have you ever faced those irritable continuous cranks when starting your motorbike? It is the result of bad spark plugs triggering from a flooded engine. It means that the worn-out spark plugs are not converting the gas into combustion, making the pistons of bikes up and down. 

2. Exhausting smell:

Exhausting Smell

The exhaust pipe will eliminate a gassy smell as the combustion chambers do not utilize the gas. The gas gets stuck on the engine, then moves to the exhaust valve, then to the pipe. Ultimately, the spark plug is not giving off the needed spark for wearing out.

3. Misfiring:

When the bad spark plugs do not arc on the tip, they don’t give off enough electricity to convert the gas. Hence, from time to time, the motorcycle starts to misfire and does not follow the rhythm while you are traveling.

4. Backfiring:

Motorcycle Backfiring

If you hear a random pop sound coming out from the motorcycle’s exhaust, then know the spark plugs are the problem! As mentioned, spark plugs combine air-fuel mixture to power the engine. But when it goes bad, the mixture gets pushed out of the chambers, thus, backfires!

What happens when motorcycle spark plugs go bad?

When a spark plug goes bad, it won’t be able to generate the spark necessary for the combustion process to occur. This will cause your bike to misfire, which can lead to problems with engine performance like slow acceleration and poor fuel economy. Bad spark plugs can also cause foul-smelling exhaust fumes and burned-out catalytic converters.

What do bad spark plugs sound like?

One sound that can indicate bad spark plugs is engine knocking. This occurs when the spark plugs or other engine elements are worn out and, instead of creating a spark to ignite the fuel, create a knocking sound instead.

Do new spark plugs make a difference?

New spark plugs are an essential vehicle maintenance item. They are responsible for igniting the air/fuel mixture in the combustion chamber, creating the powerful spark that allows the engine to run. 

While you may not always be able to detect a difference, new spark plugs create a brighter spark and ensure a smoother, more efficient running engine. When your vehicle has been in service for a while and has logged thousands of miles, the spark plugs can become fouled with oil, dirt, or deposits. 

This decreases the spark plug’s ability to create a vital spark and can reduce fuel efficiency. The plugs may also become cracked or eroded. Damaged spark plugs can cause the engine to run rough, misfire, or stop.

Motorcycle spark plug lifespan

Motorcycle owners should expect their spark plugs to last 15,000 to 20,000 miles. This range can differ depending on the make and model of the motorcycle. 

Why is my motorcycle losing power when accelerating?

The first potential explanation for losing power when accelerating could be that your motorbike’s air filters may be blocked. Over time, our air filters can get clogged with dirt and debris, restricting airflow. As a result, your bike won’t be able to get the fuel it needs to reach optimal performance. So if you haven’t done so already, replace your air filters regularly.

What happens if you drive with bad spark plugs?

Here are some of the biggest problems you can encounter if you drive with bad spark plugs:

1. Decreased Fuel Efficiency

When the spark plugs are worn and can’t produce the necessary spark energy, the fuel-air mixture won’t ignite as efficiently as it should, resulting in a decrease in fuel efficiency. This means that you’ll have to fill up your tank more often and pay more at the pump.

2. Poor Acceleration

Another common problem with bad spark plugs is poor acceleration, especially when the engine is cold and starting up. As the spark plugs weaken, they can’t provide enough spark energy to get the engine running at its maximum efficiency, resulting in poorer acceleration.

3. Misfire

In extreme cases, a worn-out spark plug can cause the engine to “misfire” – that is, some of the fuel/air mixtures may not ignite and cause the engine to shake and stall. This can be really dangerous, especially when you’re driving at high speeds.

Reasons for motorcycle spark plugs going bad

Reasons For Motorcycle Spark Plugs Going Bad

One of the main reasons that are not in anyone’s hands is obsolescence. After a certain period of use, the spark plugs go bad. Another reason is a faulty carburetor, which is not supplying enough gas to the plugs’ chambers.

Therefore, the chambers get filled with hot air that ruins the functioning of spark plugs.

When gas puts too much pressure on spark plugs, they are ready to take; it will create too much back pressure on the plugs leading them to die soon.

Lastly, oil buildup over time from the engine, which is not cleaned, gets caked inside the spark plugs’ chambers. Of this, they cannot function properly.

Spark plugs replacement routine in a motorcycle:

Spark Plugs Replacement Routine In A Motorcycle

Spark plugs are not ignorable. At some point in the bike’s life, they need replacement. Every motorcycle comes with its maintenance manual where the scheduling intervals of such things are mentioned, and every brand has a different amount of spark plugs in them.

For first-hand motorcycles, the spark plug replacement should be after every 15-16k miles of the ride. In translation to time, this equals an average of 3-5 years.

However, if you have bought a second-hand bike with engine problems that cause any bad spark plug symptoms in the motorcycle, then the replacement should be as soon as possible. In this case, the sooner, the better!

Frequently Asked Questions

How often should I check motorcycle spark plugs?

The spark plugs should be checked after a 100 mile ride with your motorcycle to see their condition. And clean the spark plugs after doubling the distance.

Can I replace the spark plugs myself?

No, you shouldn’t handle such sensitive matters unless you aren’t skilled. If displacement occurs, or the spark plugs don’t fit perfectly, then after a short time, they will wear off again due to malfunctioning. Hence, you have to spend double on another set of spark plugs plus labor.

Is it important to replace spark plugs?

No matter how much you take care of them, the spark plugs are perishable. Therefore, must replace the plugs from time to time, or else you will face those above symptoms with your motorcycle’s engine. Ultimately, the engine will stop working if the symptoms are overlooked.


It’s not a very hard or tedious job to care for the spark plugs of your motorbike. Even the slightest of care and maintenance can increase the spark plug’s life. Every three to four years, they need replacement to ensure smooth performance.

Therefore, to use your motorcycle smoothly all the time, keep these components healthy. Remember, any component that runs with electricity has to go bad someday. All you can do is try to save them as much as possible.

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