Is it Legal to Remove Your Motorbike’s Cat?

Disclaimer: We do not provide legal advice, please make your own due diligence!

There have been seemingly numerous incidents where the Police has fined riders to remove their cat from their motorbikes. By CAT, we mean catalytic converters here. Multiple motorcycle dealers have reported these incidents across the country. Replacement of exhaust system or muffler might contravene noise regulations. In contrast, removing a catalytic converter has nothing to do with noise. Instead, it has a direct connection with air pollution. In this post, we are going to find out if it is legal to remove your motorbike’s cat or not.

What is a Motorbike’s Cat?

Motorbike's catalytic converter

For those of you who do not know the purpose of this converter, it reduces emissions from your fuel combustion engine and its environmental impact.

This catalytic converter is an ugly metal box that you find mostly underneath your motorbike. This box burns red hot to lower toxic gases and the size of those pollutants present in your motorbike’s exhaust gas.

Some motorbikes experts do claim that this catalytic converter causes more asthmatic reactions because it reduces the size of airborne carbon that can infiltrate our lungs much easier.

What is Meant by Decating a Motorbike?

Removing that catalytic converter on your motorbike or decating it is one of the most common modifications you will see in the case of motorbikes.

But you also have to consider a few things.

This catalytic converter restricts the exhaust flow just like a normal exhaust can. But the two dice are placed at different distances from the cylinder head; at different RPMs, they can create different pressure wave peaks.

There is enough volume in the chests to let smaller gasses pass through without selling them down to any degree. Catalytic converters are much smaller in size and volume. Therefore, the restriction it offers will be much more linear if you compare it with engine RPM.

The back pressure wave in the exhaust chamber is critical for two-stroke engines. But it does not have any significant importance in the case of a four-stroke engine. Here, the focus is going to be on how increased flow of air will cause air-fuel ratio linear than stock.

Whether your motorbike has an aftermarket exhaust or stock end can or removed car converter. The O2 sensors in that exhaust will cope with different conditions in a closed loop. So, removing the catalytic converter will not damage your engine unless you tweak, disable, or remove the O2 sensor.

As you remove the cat converter, you will notice that your engine will start running lean. To resolve the problem, you will need a booster plug. But we will talk about this booster plugin a bit.

Is It Legal to Remove the Cat in the USA?

Is It Legal to Remove the Catalytic converter

There has been extensive legal research that took place a few years back on this topic.

The guidelines reflect EPA’S position that any pipe used to replace the section of exhaust where the catalytic converter should be, would be considered illegal under the revised Clean Air Act. Therefore, if you do any work in this area of the exhaust system, you must replace it with an approved catalytic converter.

Motorbikes are subject to these environmental laws. And once these motorbikes are registered, they become subject to the regulations in service that are applicable in a state where these motorbikes have been registered. So, for exhaust emissions, a state’s environmental protection authority is held accountable.

So, under any state’s clean air act, it is an offense to remove, impair or disconnect an engine. And some states have prosecuted different riders with pretty hefty fines that go over thousands of dollars. So, according to the law, you can remove your cat, but you will be prosecuted under environmental regulations.

What About Those Aftermarket Exhausts?

You have to check your local authorities for this one. Some states have illegalized these aftermarket exhaust systems too. Fines are not that big in this case, but riders have been prosecuted for choosing aftermarket exhausts.

Certain aftermarket exhausts are legal to use. For example, a European homologated existence is allowed in most states. Therefore, going for an aftermarket exhaust that meets certain regulations is perfectly legal to use as long as they do not enhance the overall performance of your motorbike.

But here is a thing!

Most of these aftermarket exhausts enhance the overall performance, so you will be prohibited from using any aftermarket exhaust system in most cases.

Will Use Booster Plus Resale Decating Issues?

is it allowed to use second hand catalytic converter

Yes, the booster plus and the O2 or lambda sensor will help prevent your motorbike engine from running excessively lean without the cat in your exhaust system.

The lambda sensors will adjust the air-fuel ratio within the closed-loop mode (High RPM). Therefore, decating your engine will not damage it. But when idle, or at low RPM, or during acceleration with engine braking, your engine will be running lean due to increased airflow.

It will negatively impact the motorcycle’s rideability and tends to develop terrible throttle actions after decanting it. You will also notice that your engine tends to be much easier to take off and stall when idle.

Open-loop works better with low RPM, and at low RPM, the difference in the flow of air right through the engine is not massive, whether the cat converter is there or not. The operational span of a booster plug is big enough to keep your motorbike’s engine covered both with or without the cat converter.

Are Aftermarket Exhaust Legal or Not?

Many riders prefer to go for aftermarket exhaust systems once they decat their motorbikes. But most of these exhaust systems are not legal.

We have all seen and heard those noisy exhaust systems creating a disturbance in the neighborhoods and breaking the silence at night. Local authorities and state governments have gone down hard on these aftermarket exhaust systems. Still, there is no shortage in supply or demand of this market.

The thing is, most of these exhaust systems are not approved by the Department of Transportation. Therefore, you can only go for those exhaust systems approved by the state or federal government. These systems comply with the motor vehicles act.

If you go with these aftermarket exhaust systems, you will not be prosecuted or penalized. But you have to deal with your local authorities and regulations as to which exhaust systems they allow being street or road legal.

What Do Aftermarket Exhaust Systems Do to A Motorcycle?

Exhaust Systems

Here are some different reasons why riders prefer to go for these aftermarket exhaust systems.

Make the motorbike faster

Aftermarket exhaust systems are all about going fast. The OE manufacturer has a strict budget to meet. It means that they could not produce the best exhaust systems for your motorbike at the market price.

Therefore, they went with an easier and budget-friendly design to keep the costs minimum. The emissions regulations construct these systems, and it leads to certain performance-based compromises.

Reduce your motorbike weight

You have the option of reducing your motorbike’s overall weight significantly. Most of these OE exhaust systems are made of steel or metal, and they are heavy. But you can go for those custom titanium ones that are much lighter. It can significantly improve your maneuverability and increase your overall horsepower.

Reduce maintenance costs

There are not many parts that you can change, and they significantly alter the performance of your motorbike. But your exhaust system is certainly one of those few parts that you can change. It can completely change how our bike performs. Moreover, the aftermarket options are much cheaper to maintain change too.

Change the way your motorbike sounds

It allows you to change how your bike sounds. For example, you can convert a sewing machine into a fire-breathing monster. Likewise, sports bikes that are mildly buzzy can be terraformed into something cacophonous if you truly unleash it.

Improving performance

There are various ways to improve your motorbike engine perfromance. For example, you can enlarge it or make it faster. You can also reduce the amount of air intake. But when you go for your motorbike’s exhaust system, it means that you are working on its engine efficiency.

Your bike engine is a pump. You can improve its pumping efficiency if you use a precise mix of fuel and air into it and out of it. Therefore, an exhaust that flows better will reduce engine work and perform well when it expels gases.

What Type of Exhaust Systems Should I Go For?

Different types of Aftermarket Exhausts for motorcycle

It depends upon the type of riding you do. If you are a heavyweight who carries a lot of stuff on your motorbike, you will need a different exhaust system than someone tearing down a track on a lightweight sportbike.

There are two different types of exhaust systems that you can go for:

  • You can go for mufflers only that is also known as bolt-on systems or slip-on systems. These systems retain factory head pipes, and they only replace the mufflers.
  • There are full systems available too. In this type, the exhaust will fully replace everything from the head to the back of your motorbike.

Most of the slip-on systems are typically designed to be the only thing that has to be changed. In this case, the performance boost is not going to be a major one compared to a full system. But the initial cost that you have to bear upfront is significantly low. The installation process of these muffler-only systems is much simpler too.

On the other hand, full systems alter the entire fuel system to make it work correctly. Therefore, it will typically entail a kit for a carbureted motorcycle. Plus, there will be a fuel controller for a fuel-injected bike.

This exhaust system is much more complex to install compared to mufflers-only systems. But you will get rewarded as you will get a better power gain, and your exhaust system will be much more aesthetically pleasing too.


Is it legal to decat a motorbike?

Decating your motorbike is illegal in many states as most state governments do not allow riders to decat their bikes. It is not because they make sounds, but it is because they pollute the air.

How can I decat my motorbikes within regulations?

You can use a booster plug after decating your motorbike. This booster plug will work with the O2 or lambda sensor and prevent your engine from getting damaged once you have removed the catalytic converter.

Is it better to go for a full-system replacement or a muffler-only system?

If you are on a tight budget, then a better option for you is to go for a muffler-only system. But if you are looking for high performance, a full modification is mandatory. Of course, it will cost you much more, but it will also improve your motorbike’s performance trifold.

Do all exhaust systems make the engine sound loud?

No, not all exhaust systems make the engine sound loud. It is up to you what you are looking for first. There are different options available for you to choose from. You can make a choice based on your budget, based on how much sound you want it to make, and how much horsepower it can produce. But you might have to check your local or state government rules on exhaust systems too.

What does straight piping mean?

Straight piping also means removing the catalytic converter for your motorbike. When you remove the cat converter and the muffler, the existing pipe that remains is just parallel to the ground, and it is short because it only contains the exhaust header. But this practice is illegal.


Straight piping or decating your motorbike, whatever you call it, is illegal in most states. And it has nothing to do with the sound. Instead, it is about air pollution.

You can decat your motorbike, but you will have to use an aftermarket exhaust system that compares with your state’s Department of Transportation. Otherwise, prepare yourself for some hefty fines.