What Are Dirt Bike Valves? Function, Adjustment, and Signs of Problems [2023]

Dirt bike valves are one of the most important parts of the engine, and yet they are often overlooked. Valves control the intake and exhaust of air and fuel mixture into and out of the engine cylinders. They are opened and closed by the camshaft, which is driven by the crankshaft.

Dirt bike valves need to be tough to withstand the high temperatures and pressures inside the engine, as well as the abrasive action of the fuel mixture. They are made from steel or titanium, and can be either solid or hollow.

Hollow valves are lighter and cooler than solid valves, but they are also more fragile and can break more easily. Solid valves are heavier but can take more abuse. Valves are an important part of the engine, and it is important to choose the right type for your dirt bike.

What are valves?

Valves are one of the most important components of an engine, and they are also one of the most vulnerable. Valves control the flow of air and fuel into the combustion chamber, and they also help to regulate the exhaust gas outflow. The valvetrain is made up of a series of valves, each with their own specific function.

Dirt bike valves are designed to withstand the rigors of off-road riding, but they are still susceptible to damage from debris and rocks. It is important to check your valves regularly to make sure they are in good working order.

Valve problems can cause a loss of power and efficiency, so it is important to catch any issues early on. If you think there may be a problem with your valves, take your bike to a qualified mechanic for inspection.

What are dirt bike valves?

Dirt bike valves are essential for the proper functioning of your bike. They are responsible for controlling the air and fuel mixture that enters the engine, and play a vital role in the combustion process.

Dirt bikes typically have four valves – two intake and two exhaust. The intake valves allow fresh air to enter the engine, while the exhaust valves allow spent gases to exit. Both types of valves are opened and closed by the camshaft, which is driven by the crankshaft.

Valve clearance is critical on a dirt bike, as it ensures that the valves are opening and closing at the correct time. If clearance is too tight, the valves will not open fully and will cause poor performance. If clearance is too loose, the valves will open too early and can cause valve float, which can lead to serious engine damage.

It’s important to check your valve clearance regularly, as it can change over time due to wear or temperature changes. Adjusting valve clearance is a relatively simple task that can be performed with basic tools. Consult your owner’s manual or a service manual for specific instructions on how to adjust valve clearance on your particular bike.

The Function of Dirt Bike Valves:

Dirt bike engines have two types of valves: intake valves and exhaust valves:

a. Intake Valves:

  • Intake valves allow the air-fuel mixture to enter the engine’s combustion chamber during the intake stroke.
  • They open and close at specific times to ensure efficient air and fuel flow for combustion.

b. Exhaust Valves:

  • Exhaust valves are responsible for expelling the burned gases from the combustion chamber during the exhaust stroke.
  • They open and close at precise intervals to facilitate the smooth evacuation of exhaust gases.

c. Valve Timing and Performance:

  • Proper valve timing is crucial for optimal engine performance, ensuring the right amount of air-fuel mixture and efficient exhaust gas expulsion.
  • The timing of the valves is controlled by the camshaft, which rotates in sync with the engine’s crankshaft.

Importance of Valve Clearance:

Valve clearance, the small gap between the valve stem and the rocker arm or valve lifter, is vital for engine performance and longevity:

a. Valve Clearance and Engine Performance:

  • The correct valve clearance ensures that the valves open and close precisely according to the manufacturer’s specifications.
  • Proper valve clearance promotes efficient combustion, power delivery, and overall engine performance.

b. Effects of Incorrect Valve Clearance:

  • Insufficient valve clearance can cause valves to stay partially open, leading to loss of power and poor performance.
  • Excessive valve clearance may result in valve tapping, reduced compression, or even valve damage.
What Are Dirt Bike Valves?
What Are Dirt Bike Valves?

Checking and Adjusting Dirt Bike Valves:

Follow these steps to check and adjust the valves on your dirt bike:

a. Tools Required:

  • Feeler gauges
  • Wrenches
  • Screwdriver or socket set
  • Service manual for your specific dirt bike model

b. Step-by-Step Valve Adjustment Process:

  • Consult the service manual for the recommended valve clearance specifications and the appropriate adjustment procedure.
  • Remove the necessary components to access the valves, such as the valve cover.
  • Use the feeler gauges to check the clearance between the valve stem and the rocker arm or valve lifter.
  • Adjust the clearance by loosening the locknut and turning the adjuster screw until the proper clearance is achieved.
  • Once adjusted, tighten the locknut while holding the adjuster screw in place.
  • Repeat the process for each valve, following the specific sequence and clearance specifications outlined in the manual.

c. Recommended Valve Clearance Specifications:

  • Valve clearance specifications can vary between different dirt bike models and engines.
  • Consult the service manual or contact a qualified mechanic to ensure you have the correct clearance specifications for your specific dirt bike.

Signs of Valve Problems:

Be aware of these common signs that may indicate valve problems in your dirt bike:

a. Ticking or Clicking Noises:

  • Unusual ticking or clicking sounds coming from the engine can indicate valve clearance issues or worn valve components.
  • These noises may become more noticeable during acceleration or at higher RPMs.

b. Loss of Power or Poor Performance:

  • If your dirt bike experiences a loss of power, struggles to reach higher speeds, or has reduced throttle response, it could be due to valve problems.
  • Incorrect valve clearance or worn valves can affect the engine’s ability to breathe properly and perform optimally.

c. Hard Starting or Backfiring:

  • Difficulty starting the engine or backfiring during starting or deceleration can be signs of valve problems.
  • Valves that are not closing properly or have incorrect clearance can disrupt the combustion process, resulting in these symptoms.

The benefits of having dirt bike valves

One of the benefits of having dirt bike valves is that they can help improve the performance of your bike. Valves can help improve airflow into the engine, which can lead to increased power and efficiency. Additionally, valves can help reduce engine vibration, which can make your ride more comfortable and enjoyable.

How to clean your dirt bike valves

If your dirt bike has a four-stroke engine, there are two valves per cylinder: an intake valve and an exhaust valve. The intake valve opens to let fresh air/fuel mixture into the cylinder. The exhaust valve opens to let the spent air/fuel mixture out of the cylinder. Both valves are closed during the compression and power strokes.

Dirt and debris can build up on the valves, causing them to stick or not seal properly. This can lead to poor engine performance or even engine damage. That’s why it’s important to clean your valves regularly.

Here’s how to clean your dirt bike valves:

1. Remove the spark plug from the cylinder you’re going to be working on. This will prevent the engine from accidentally starting while you’re working on it.

2. Use a valve adjustment tool to loosen the rocker arms so that you can access the valves.

3. Use a brush and some cleaner to remove any dirt and debris from the valves and valve seats. Be careful not to damage the delicate surfaces of the valves or seats.

4. Use a rag or compressed air to clean out any remaining dirt or debris in the area around the valves.

5. Reassemble everything, being careful not to over-tighten the rocker arms (this can damage the valves).


In conclusion, dirt bike valves are an important part of the engine and need to be well maintained in order to prevent damage. It is recommended that you check your valves at least once a year and more frequently if you ride often. With regular maintenance, your valves will last for many years and keep your dirt bike running smoothly.


John Webler a writer for Offroadbible
John Webler

Hi there, I'm John Webler, the owner and a writer for Offroadbible, a website that covers everything related to ATVs, dirt bikes, and UTVs. As a lifelong off-roading enthusiast, I have a deep passion for exploring the great outdoors on two and four wheels. I have spent countless hours tinkering with engines, navigating rough terrain, and pushing the limits of what these machines are capable of.

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