What are Valves on a Dirt Bike?

In every engine, whether it is 2 stroke or 4 strokes there is an intake and exhaust system available. Whether it is a two-wheeler or four-wheeler this all has a fluid intake system through which in the combustion chamber oil is supplied. But the question arises here what are the valves on a dirt bike?

Whether it is spark plug ignition or combustion engine these all work on the phenomenon of intaking fluid from the fuel tank and then it is burnt inside the cylinder which outputs the power by after one power stroke. So here today we will discuss what are valves on a dirt bike and its function and what is its necessity?

What are Valves?

Before getting into the deep first we have to understand in simple words what is a valve? How does it work and what is its working principle? Everywhere there is some mechanism is in process and understanding the phenomenon of the mechanism can be helpful for people who are in the field of riding.

So let’s discuss what is dirt Bike valve?

A valve is a mechanism that controls the flow of fluid by allowing and disallowing it. If you talk about floats it means there are liquid and gases also included and this kind of substances can flow really so valves are used here for controlling them.

Valves control flow of fluids different types of systems like pneumatic and hydraulics, motors, generator, etc.

When we talk about the valves are the mechanical devices that control the flow and pressure inside a system it can be a process. These are basically implemented in a piping system that helps to flow liquids such as gases, vapours, and oil.

There are many different types of valves are available like the globe, plug, butterfly, globe, gate, diaphragm, control valves, pressure relief, and pinch valves.

All have different numbers of models and each with several features and functional abilities. Some walls are manually operated while others are self-operated. The manual operated comes with an actuator hydraulic or pneumatic systems.

Manual valves are generally operated by pedals, hand nobs, levers or wheels. Some of the valves have a geared system which mechanical works inside that actuate the valves ball for Disc against its seat it also includes sometimes gasket.

A valve can control fluid flow to many ports, not in a single or double port. These are having different costs and sizes from smallest to biggest. Being a beginner you may be acquainted with how does a clutch work on a dirt bike?

What is the function of the Valves?

When we talk theoretically then the valve operation is said to be very simple. The camshaft pushes the valve down into the cylinder that goes against the spring which helps to open the valves. After opening the valve’s air-fuel mixture floors and it enters into the combustion chamber and then it lets the valve shut due to the spring force.

But nobody has imagined that this process is really very fast with a dirt bike engine which revolves around at 10000rpm, let’s say each valve has to open and close 83 times per second so it has to move very fast. So the speed is the main problem for the wall which has to consist of a lot of energy and it is repeatedly slamming into the valve seat.

Valve timing is really a critical issue. Designers of the engine can set exactly when the inlet and exhaust valves will open and close and how long they will be open by changing the orientation of the camp and their profiles.

Dirt bike engine works in the same way in which a car engine works. Inside the engine, it is consists of a cylinder Block one head and a piston which contains the valve train.

In this process, the Piston moves up and down inside the cylinder block which is driven by the explosion of the air-fuel mixture which has been ignited by a spark. For generating The Spark there one spark plug is used.

Valves open and close that allowed the air-fuel mixture inside the combustion chamber. The Piston helps to rotate the crankshaft which transforms the energy from the Piston into a rotary motion. The rotational force of the crankshaft now submitted by the transmission system to the rear wheel of the dirt bike.

Dirt Bike engines have been classified normally in different characteristics:

  • Number of strokes generated in the cycles
  • The capacity of the combustion chamber
  • Number of cylinders they posses

Construction of the valves

It is shaped like a 4-inch little finger with a big flathead. Nowadays in all modern bikes, the valves head which is also called as face lies in the combustion chamber with the shaft which is called the stem which poking up out of the cylinder where it is is connected with the spring.

Different methods of activating valves some of the Older engines have rocker arms connected to a shaft which is operated by cams down by the crankshaft and in modern bike Desmodromic system is used.

But I would like to share you the normal configuration which is also known as the most common configuration that is called as the double overhead cam in which which which one of the two camshafts operating two inlet valve per cylinder and others operating the two exhaust valves per cylinder.


Inside a dirt bike engine, there are a lot of parts which results in a powerful riding and different kind of stunts. It is not just one part that is responsible for performing and power on the bike. If the clutch is important then gearbox, carburettor, valves, and wheels are also very important.

So in this post, we have talked about what is falls on a dirt bike and how they function and what is the significance of using them inside a bike. Most probably all are aware of the necessity of valves inside a dirt bike engine. I hope we have given you enough information about the valves which are used on the dirt bike and if you have any query you can ask by using our comment.

Sources: What are valves, Valves general, How does a dirt bike valve work