Here’s What Happens When You Decat A Motorcycle


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You may or may not have heard of the term “decatting” your motorcycle. There are a lot of people who will tell you that this will improve your motorcycle’s performance and others who will tell you it will get you a ticket. 

So, what happens when you decat a motorcycle? When you decat a motorcycle, the performance as well as the fuel mileage will improve slightly.  However, removing the catalytic converter on a motorcycle also results in increased emissions, louder exhaust, and an impacted resale value.

Decatting, also known as de-catalyzing, is the process of removing the catalytic converter from a motorcycle. The catalytic converter is an emission control device that reduces harmful pollutants from the exhaust system. Removing this device can increase the performance of the motorcycle, but it also has significant drawbacks.

What Happens When You Decat A Motorcycle?

Removing the catalytic converter on your motorcycle may seem like an easy enough task to perform. It’s important to remember that any time you remove something stock from your motorcycle, there’s going to be some changes in the way your motorcycle performs. Some of those changes may be desired while others may be unexpected.

Catalytic converters restrict the flow of exhaust from the engine.  This, in turn, creates back-pressure on the engine and can decrease the performance altogether.  Removing the catalytic converter will ensure a smooth flow which can result in better performance and more horsepower. 

It is also thought that removing a catalytic converter from a motorcycle may also increase gas mileage.  Since the engine doesn’t need to work as hard to push out the exhaust, that means less fuel is consumed. This does, however, depend entirely on the type of motorcycle you have.  Others may argue that removing the catalytic converter doesn’t have any impact on fuel mileage.

While decatting may offer these benefits, it also has several drawbacks that riders should consider before making this modification.

One of the primary impacts of decatting is increased emissions. Without a catalytic converter, the motorcycle’s exhaust system is no longer able to filter out harmful pollutants, leading to higher levels of emissions. This can have a negative impact on air quality and the environment and may result in violation of local air pollution regulations.

Another consideration is the potential for increased engine noise. Without a catalytic converter to muffle the sound of the exhaust, the motorcycle will be louder which can be a concern for some riders. The increased engine noise can also make it difficult to communicate with passengers or other riders while on the road.

Finally, decatting a motorcycle can also impact its resale value. Many potential buyers prefer motorcycles that are emissions compliant and have a catalytic converter installed, so removing this component can reduce the motorcycle’s ability to sell.

Is It Legal To Decat A Motorcycle?

The legality of decatting a motorcycle, or removing its catalytic converter, varies depending on where you live. In some states and countries, decatting is completely legal, while in others it is prohibited by law. Before making any modifications to your motorcycle’s exhaust system, it is important to familiarize yourself with the laws and regulations in your area.

In the United States, decatting a motorcycle is only legal in certain states. In some states, removing the catalytic converter is illegal and can result in fines, impoundment of the vehicle, or even criminal charges. In other states, decatting is legal, but only if the motorcycle is used for off-road or racing purposes. If you plan to use the motorcycle on public roads, it must have a catalytic converter that is compliant with emissions regulations.

In the European Union, decatting a motorcycle is generally prohibited by law. The EU has strict regulations regarding emissions from vehicles, and the catalytic converter is an important component of a motorcycle’s exhaust system that helps to reduce emissions. Decatting a motorcycle can result in higher emissions, which is in violation of EU law.

Not all motorcycles require emissions testing, but there are a few out there that do.  A motorcycle will fail an emissions test if the catalytic converter is removed and if this fails, the owner will not be able to register their motorcycle and receive a license plate to legally drive on public roads.  This has a domino effect and can greatly hinder a rider if their motorcycle does require emissions testing.

It is also important to consider the potential consequences of decatting a motorcycle beyond the legal implications. While removing the catalytic converter can increase engine performance, it also results in increased emissions, increased engine noise, and a reduced resale value, among other impacts.

Is It Harmful To You And The Environment To Decat A Motorcycle?

Decatting a motorcycle, or removing its catalytic converter, can have negative impacts on both the rider and the environment. While some riders choose to decat their motorcycles for performance or aesthetic reasons, it is important to consider the potential harm before making this modification.

As mentioned before, one of the primary concerns with decatting a motorcycle is increased emissions. The catalytic converter is an important component of a motorcycle’s exhaust system that helps to reduce emissions and filter out harmful pollutants. When the converter is removed, the motorcycle’s exhaust system is no longer able to filter these pollutants, resulting in higher levels of emissions and a negative impact on air quality.

Decatting a motorcycle can also contribute to environmental degradation. The pollutants emitted from the motorcycle’s exhaust system can harm plants and wildlife and contribute to the overall degradation of the environment.

Be aware that removing the catalytic converter can be harmful to you as a rider.  First, consider the emissions imprint we’ve already discussed.  You’re already exposed to exhaust while you’re riding a motorcycle, especially while you’re idling.  On top of the regular exhaust you’re being exposed to, you’re also inhaling other harmful fumes the catalytic converter would otherwise filter out.

Decatting a motorcycle also makes for a louder environment for you and those around you.  While this in itself isn’t harmful to your ears, it can be harmful in the sense that you can’t hear as much of what’s going on around you. It’s risky not being able to hear someone’s horn honking as a warning.

Will Removing The Catalytic Converter Improve Motorcycle Performance?

Many riders consider removing the catalytic converter from their motorcycles in the hopes of improving performance. However, the reality is that the impact of decatting has on performance is not as straightforward as it may seem.

In theory, removing the catalytic converter should free up the flow of exhaust and improve performance. Think of this in comparison to blowing through a straw.  Having a piece of material in the straw (aka the catalytic converter) will make blowing through the straw much more difficult.  Once that piece of material is removed, blowing through that straw is much easier.

The exhaust is able to move smoothly through the exhaust pipes which, in turn, can result in a better performing engine and slightly more horsepower.  It can also result in better acceleration.

However, the impact on performance is not significant and may not be noticeable to the average rider. In some cases, the increased engine noise associated with decatting can actually detract from the overall riding experience.

It is also important to consider the potential long-term consequences of decatting on the motorcycle’s engine and performance. Over time, the increased emissions and decreased fuel efficiency can lead to engine damage, which can have a negative impact on performance and result in costly repairs.

While removing the catalytic converter from a motorcycle may seem like an easy way to improve performance, the reality is that the impact is not significant and may not be that noticeable. Be sure to familiarize yourself with the laws and regulations in your area about whether or not it’s legal to decat your motorcycle and consider the negative impacts it may have on your riding experience.

This article has been reviewed in accordance with our editorial policy.

Kyle Cannon

Kyle currently works as a mechanical engineer and graduated with a minor in automotive engineering. He loves restoring motorcycles, has a vast knowledge of how they work, and has sold his restoration projects to customers from all over the United States.

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