Why Are Dirt Bikes So Loud?

Have you ever heard the thunderous roar of a dirt bike drive past you and wonder why the noise was so loud? Today I want to help you understand why that is.

Dirt bikes are loud because of their short mufflers, their high RPMs, and how often they are accelerating instead of cruising. Two-stroke dirt bikes are generally louder than four-stroke dirt bikes, but the noise from a four-stroke bike will carry further.

Obviously, there is more to dirt bikes than simply mufflers and short pipes. To learn more, keep reading!

Where Does the Noise Come From?

There are plenty of things that affect how loud a dirt bike is. It is really hard to determine which one of these is the main culprit of the noise, but they all contribute in some way to the loudness of the bike.

RPM

It may sound like a simple answer to a simple question, but the faster or slower you go depends on the range the sound of your dirt bike can create. With a two-stroke dirt bike, the problem with its pitch is the way the adjustable-power-valves operate. When the valve opens at different rpm, it will cause erratic noise levels to be forced out of the chamber.

The four-stroke dirt bike experiences the same variation in noise level, but instead with the carburetor settings. Depending on the width and length of the carburetor is the effect it has on the noise of the dirt bike. All of these factors come from the RPM of the bike, which can create a noise that is high pitched and may appear as a squeak, or deep and resonating due to the mechanics of the bike stated before.

Two-stroke bikes are louder, but the sound doesn’t carry as far because of its high pitch. On the contrary, with four-stroke bikes, because of the difference in exhaust and combustion, their pitch is deeper and more resonating, which carries farther than the two-stroke.

Mufflers and pipes

There are a few different spots inside the dirt bike as to where the noise is coming from. The loud noise comes from the muffler, but it can get even louder due to the different types of mufflers, such as a chambered-muffler, a straight-through muffler, and a turbo style muffler.

Within the dirt bike itself, the pipes vary in length, causing a quicker burst of energy to escape the bike. Along with this information, there are two different bikes, the two-stroke, and the four-stroke, that have varying sounds depending on the factors stated before.

When the pipes of a bike are shorter, the engine is more quickly outputted, thus creating a greater sound than those of a bike with the proper lengths. While the bike is in it’s building stage, there are questions in regards to how long and wide a pipe should be, which is taken into consideration for the overall performance of the bike.

When it comes to the muffler, the three stated above all perform different tasks. A chambered-muffler has grooves in its piping in order to cause friction, which will lessen the sound that comes out at the end. A straight-through muffler is standard piping, in which case some of the noise is absorbed as it passes through the pipe, and doesn’t cause as much sound unless it were to be shortened and there was less friction between the exhaust and the piping. The final type of muffler is the turbo style muffler, which is shaped like an “s” and takes most if not all of the sound away, deadening into the air around it. The different piping and mufflers put on a bike can drastically change the sound coming out of the dirt bike.

2-Stroke vs 4-Stroke

The difference between a two-stroke and four-stroke dirt bike is the number of times the piston in the engine moves back and forth, causing the gasoline and chain reactions within the engine itself. The difference in the number of times the piston pushes exhaust out greatly influences the sound of the dirt bike.

A four-stroke dirt bike works in a series of injection, compression, ignition, and exhaust. When the piston pushes down the second time, the exhaust is released, which isn’t creating as much of a commotion within the dirt bike.

With a two-stroke bike, each time the piston pulls back, combustion is happening, causing the bike to be considerably louder than a four-stroke dirt bike. The way these two bikes work is drastically different, resulting in two different releases, neither resulting in the same sound.

Wear and Tear

Not only do bikes have different parts that can create a higher or lower noise, but also how old and often a bike has been used. With age, parts begin to wear down, causing the bike to make undesirable noises. It is important to keep up with the parts on your bike, as not only do parts begin to wear thing, but they can also grind upon one another and create other noises not solely because of the engine or the muffler.

How loud is a dirt bike

There are a few different aspects to consider when understanding the decibels of a dirt bike and where the noise comes from. Some factors to consider with the noise level of a dirt bike is not only the make, model, and pipes used in the formatting of a dirt bike, but also the rpm’s of a dirt bike. It may seem like a silly answer to this question, but how fast or slow you’re driving can cause the dirt bike to develop varying noises.

According to a study done in California, the comfortable sound a dirt bike should make is 96 decibels, which is more like a quiet roar. Of course, each state has different laws according to how raucous a dirt bike can be, and which parts are used to create such noises. The decibel of a dirt bike ranges, but it is all dependent upon the way it is developed and the rate of speed that the bike is going can greatly affect it’s overall performance and noise level.

How to decrease noise

Whether your bike is brand new or has seen its fair share of the mud and grime of the dirt tracks your ride, your bike may need some service to decrease the noise level that is upsetting your neighbors. As stated before, as a bike gets older, parts begin to wear thin or become loose, thus creating more noise. First, check your muffler. Depending on what type of muffler you may have is how much noise is being absorbed, which is an easy fix. Next, check the parts of your bike. Is the tubing air-tight and all of the nuts and bolts securely placed so that nothing is rattling around? There are simple ways to fix a dirt bike so that the noise that is being produced isn’t causing others to question why you were allowed to have the bike in the first place. Ensure that your bike is working according to the laws placed in your state or city, as the decibels it produces greatly bothers others.

Jim Harmer

I'm the co-owner of DBP. I live in Star, Idaho and enjoy dirt biking with my wife and two boys throughout the Idaho mountains.

Recent Content