Four Signs Your Motorcycle Spark Plugs are Bad

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If you’ve owned a motorcycle for more than a few years, you’ve probably run into a few issues with the sparks plugs. This is particularly true if your motorcycle is an older model.

Although they are very small, spark plugs are essential to the engine’s functionality. If there’s any part of them that is malfunctioning, that could mean your whole motorcycle acts up and gives you problems.

What are the symptoms of bad motorcycle spark plugs You may notice your motorcycle misfiring or backfiring frequently, as well as a flooded engine. Also, look out for any physical signs such as burn marks, corrosion, or broken tips.

Throughout my motorcycle riding years, I’ve replaced hundreds of spark plugs mostly because the motorcycles I restored required it. I’ve been able to learn a thing or two about them through my experience as a motorcyclist and can report what I’ve learned.

Bad Motorcycle Spark Plugs

Bad spark plugs can cause problems on motorcycles. It is often difficult to identify the problem. You can be more prepared for the future by knowing the symptoms of bad sparkplugs and will be able to fix your motorcycle faster.

Each motorcycle’s spark plug count will vary depending on the number and type of cylinders inside it. The bigger the engine your motorcycle has, the more likely you’ll run into spark plug issues because you’re dealing with more of them.

Misfiring is the first sign your motorcycle’s spark plugs may be going bad. Misfiring occurs when your motorcycle runs on a steady beat but it starts to drift for a while before picking up its rhythm again. Think of it like the bass player in a band; you can obviously tell they’re off because the rest of the music doesn’t sound right.

The spark plug is not arcing at its tip at the correct time, which can cause misfiring. If it doesn’t arc and give off electricity at the right time, the gas it’s supposed to mix with isn’t where it should be and combustion is then thrown off.

The second way you can tell your motorcycle spark plugs are going bad is if it’s backfiring. Backfiring occurs when the exhaust produces loud, irregular pops. This happens because the spark plugs produce an intermittent spark.

An intermittent spark is when the spark plug usually fires just fine most of the time, but every once in a while it just won’t spark and your engine will backfire.  When there is fuel and air in your cylinder and the spark plug doesn’t ignite it, it gets pushed out of the cylinder on the compression stroke and as soon as it hits the hot exhaust header it combusts. For more reasons why your motorcycle can fail, see my article.

Flooded engines could also indicate bad spark plugs. When your motorcycle cranks incessantly without starting, it is called a flooded engine. You will notice a strong stench of gas.

When a motorcycle engine becomes flooded, that means the combustion chamber is filling with gas but isn’t being combusted. The carburetor or fuel injector continue to give the appropriate air and fuel ratio to a dysfunctional spark plug that isn’t arcing and isn’t creating the combustion needed to move the pistons up and down. Check out my article about what you should do if your motorcycle engine floods.

Your motorcycle could have bad spark plugs if your exhaust emits a strong gas smell or you see a lot of gas coming out of your pipes. If the spark plug is bad and isn’t giving a spark at the right time, left over gas in the combustion chamber gets sucked into the engine, doesn’t combust, gets past the exhaust valve, and shoots out the exhaust pipe.

If you do notice some sort of liquid coming out of your exhaust pipe, make sure it isn’t water. Condensation can sometimes build up in the exhaust pipe and leak out when the motorcycle starts.

If you suspect that your spark plugs are not working properly, you should also inspect the spark plugs themselves. There are obvious clues that will show that the spark plug is bad such as any burn marks, if it’s completely white, if any parts of the nobs are broken or bent, or if there is any rust or corrosion at all.

Any of these ailments on a spark plug can cause the spark plug to delay it’s electric arc or simply not spark at all, especially if there’s any type of corrosion on the end.

Why Spark Plugs Go Bad

Once you have figured out that bad spark plugs are the problem, you’ll probably want to know how to prevent this problem in the future. Don’t feel too bad if you end up having to replace your spark plugs because The number one reason that they get old is because of their age.

We wish all spark plugs would last forever, as well as any spare part that you purchase!). The nobs at the spark plug’s end will wear down over time and stop sparking. Anything to do with electric components in a vehicle is likely to go out sooner than the other parts, even if all is well.

Bad timing on your engine could cause the spark plugs to fail much sooner than they are expected. If your gas is detonating too early or too late inside the combustion chamber of the engine, all of that back pressure is going to build up on the spark plug since the pressure doesn’t have anywhere else to go.

Motorbikes that are running lean can quickly wear out their spark plugs. This is because the fuel injector or carburetor isn’t putting enough gas into the combustion chamber. The gas that does get inserted burns much hotter because there’s more air than there should be. This higher temperature can warp spark plugs, bend them and even cause permanent damage within days.

How often should you change your spark plugs?

When I discover that my motorcycle is having problems with its spark plugs, I feel relieved. Spark plugs are a quick and inexpensive fix that can be done in under an hour.

You can ride your motorcycle for years until you notice it’s acting up due to bad spark plugs, but you should probably take a look at them before they start giving you trouble. It is recommended that motorcycle spark plugs be replaced every five-years. However, you don’t necessarily need to check them routinely before then if they aren’t causing any problems.

You should replace all spark plugs at once if you have to. Again, spark plugs are inexpensive and easy to change so you might as well change all of them while you’re at it. One spark plug can cause a fire, so it is likely that others will follow suit.

How to Replace Bad Spark Plugs

You will only need a few basic tools and a couple of dollars to replace your spark plugs. It will take you about an hour. If you’re changing out your spark plugs, the first thing you’ll need to do is disconnect the battery to remove any risk of shock.

The next thing you’ll need to do is remove all the spark plug boots off of the spark plugs. These can be easily removed by a gentle tug. The back end of your spark plug will now be exposed. These ends can be removed with a socket wrench because they are shaped like nuts. Most spark plugs measure 5/8″.

Rubber gaskets can be found in special sockets. So after unthreading the sparkplug, the socket will be able pull it out for your. It is sometimes difficult to access spark plugs so this tool comes in handy.

Many people believe that the spark plugs are already at the correct distance when they purchase new ones. This actually isn’t true and you need to set the correct gap yourself.

This tool looks almost like a silverdollar and has a ridge running around its edge. It is narrower than it is wide (pictured above). This tool is easy to use to adjust the gap at the tip your spark plugs. You’ll need to look in your owner’s manual or look online to see what gap you should have with the spark plugs specific to your motorcycle.

Once you set the appropriate gap on your spark plug, you’ll need to coat the outside of the spark plug with anti-seize. Most motorcycle engine blocks are aluminum, so when you thread a steal spark plug into an engine block the two metals want to seize together because they’re different from each other. This can be prevented by the anti-seize product.

With your socket wrench, you can now thread all your spark plugs into your engine. Reinstall the spark plug boots, and connect the battery to the motorcycle.

Similar Questions

How can I reduce the gap between a spark plug and a spark plug? If you feel the gap on the spark plug is too large, gently press down with your hands. You can push it down with your hand by pressing the side electrode against a hard surface. Make sure to check the gap once you close it a little to ensure it’s at the right gap distance.

How often should my motorcycle be serviced? Oil on a motorcycle should always be changed after 4,000 miles, or six months, depending on which comes first. The same schedule should be followed for lubricating and checking the tension of the chain. Every month, tires should be checked. Tuning the carburetor and flushing of the cooling system should also be done every other year. You can read my article for more details.

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