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What Are the Bad Valve Adjustment Symptoms and How to Solve

Have you ever noticed that your lawn mower isn’t working as well as it used to, or that it’s leaving a trail of clumps in the grass when you finish mowing? It’s possible that your valves are out of adjustment. 

Valve adjustment is a pretty simple process and is something nearly anyone can perform with a little time and patience. So if your mower is having trouble, take a look at this guide to get it running and cutting like new again.

Lawn mower valve
Lawn mower valve

Symptoms of Lawn Mower Valve Adjustment

Lawn mower valve adjustment is important to keep the engine running smoothly. However, if you skip adjusting the valves at the right time, you will face several problems. We are going to discuss the most common symptoms of lawn mower valve adjustment.

Valves are an essential part of any combustion chamber engine. They allow air and fuel to enter into the combustion chamber, and exhaust to leave it. Without these valves, your lawn mower would not run at all.

Valves are delicate and require precise timing for smooth running of the engine. If your lawnmower starts showing signs of trouble in starting or running, check its valves first before doing anything else with it.

Valve Adjustment Symptoms

Your lawn mower may show signs that its valves need some fine-tuning. Here are a few common symptoms-

  1. Excessive tapping noise all on a sudden
  2. Starting cord is very hard to pull
  3. Fuel consumption is too much
  4. Power loss all on a sudden
  5. No compression
  6. Oil Leaks

Excessive Tapping Noise

The valves of an engine are important components of the entire engine. The valve is used to control the flow of gas in and out of the engine. This means that they are connected to both the intake and exhaust manifold. There are two types of valves: inlet and exhaust. In order to ensure that everything is working fine, it is necessary to adjust these valves periodically.

Tapping noise is a symptom of lawn mower valve adjustment. In case you have experienced such a noise, you should never ignore it. An increase in the valve gap means increased tapping noise; hence, it should not be ignored at any cost. If you are hearing this kind of noise from your engine, then it is definitely a good sign because you can fix it asap rather than waiting for other worse symptoms to come up and cause more damage to the engine.

Starting Cord is Hard to Pull

If you have noticed that your lawn mower starting cord is very hard to pull, then it’s possible that you need to adjust the valves on your lawn mower. Why? If a valve isn’t adjusted properly, it will close too soon and the engine won’t be able to build enough compression for combustion. 

Starting Cord is hard to pull
Starting Cord is hard to pull

It indicates increased or decreased tappets. It can cause decreased efficiency and power of the mower. It can also lead to increased fuel consumption because the mower will keep running for a long time without providing any extra performance. 

This can cause a number of issues including a reduction in the power output of the engine and an increase in fuel consumption when compared to an engine with properly adjusted valves.

If this sounds like something you would like to avoid, then make sure that you consider adjusting the valves on your lawn mower as soon as possible.

Hard to Start

A lawn mower engine that has a hard time starting, or a difficult time staying running may have an issue with the engine valve clearance. Valve clearance should be checked at every tune-up, and it is essential that the valves are set correctly before you attempt to start the engine.

Hard to start
Hard to start

A lawn mower engine that is in good working order will have no problem starting. A properly tuned up engine that has valve clearance issues will not run smoothly and can experience a hard time cranking or keeping itself running. It will often run best when warm. 

You should know your lawn mower hard starting is a symptom of lawn mower valve adjustment. You need to make sure that your valves are adjusted properly so that you can get rid of this problem. You might also experience your mower turns over but doesn’t start sometime.

Less Compression

If your lawn mower won’t start, it may be because the valves of your engine are not correctly adjusted. The mower may have little compression, or it may not have any at all. This problem can be fixed with a simple lawn mower valve adjustment tool and a screwdriver.

Lawnmowers are made up of hundreds of parts, and if any one of them fails, you will have an issue with the machine’s performance. One of the most common problems with lawnmowers is an engine that won’t start.

That being said, there are several reasons why your lawnmower won’t start. For example, if it doesn’t get enough fuel, has clogged filters, or has worn spark plugs then the problem can be easily fixed by replacing these parts. However, if the valves aren’t adjusted correctly then it will be harder to fix this problem.

When your valves aren’t adjusted properly, they either allow too much air to enter the combustion chamber or too much air to escape it. This can result in less compression which means that there won’t be enough power to run the engine.

Cord is Hard to Pull

A lawnmower has a compression release mechanism that helps in starting the engine. Due to this, you don’t need much power to pull the cord. The valve opens and releases some of the pressure in the cylinder so that it becomes easier for you to pull the cord and start your engine. 

However, if there is a fault in this mechanism, it will be harder for you to crank up your lawnmower. If that is the case, you should check out the compression release mechanism of your lawnmower and repair it if necessary.

The carburetor needle is another reason which makes the starting cord become hard to pull. If your lawn mower has a faulty carburetor needle, the lawn mower will be hard to start. So you should check if the carburetor needle works fine.

The last reason is that the flywheel brake and key are faulty. The flywheel brake and key mainly used for stopping the engine, but if it doesn’t work well, it will also make the starting cord become hard to pull. 

Hence, if your lawn mower has one of these problems mentioned above, you should take corresponding measures to repair them as soon as possible so that you can start your lawn mower smoothly again.

Why you should adjust valve in your lawn mower?

Valve Adjustment in a lawn mower is important for many reasons. First of all, the right opening and closing times of the valves must be guaranteed to prevent damage to the engine. 

For example, if the valve clearance is too little and the valves open too early, they can hit against the piston. If they open too late, they can open while the piston is already coming down again. 

This has an adverse effect on the performance of your engine and may cause it to explode. A precise valve adjustment results in improved performance and good engine mileage. 

In addition, enough space for thermal expansion must be provided during operation. This ensures that your engine does not overheat or burn out. Of course, a good valve adjustment also results in lower fuel consumption.

Frequently Asked Questions

What are the symptoms of a bad valve adjustment?

The symptoms of a bad valve adjustment can sometimes be the bike’s misfiring, an engine running rough, hard on gas status or engine noise. There can also be symptoms of air leaking system or not enough air allowing for uneven starts.

A simple visual check is all it takes to determine whether the bike requires an immediate follow-up visit or if the adjustments just need fine tuning. Ensure that your mower is running on all cylinders and with maximum power in between services.

What happens if valves are not adjusted properly?

If the valves are not adjusted properly, the engine will not run at peak efficiency, and you may experience a rough idle. If there’s too little valve clearance, the valves won’t fully close, causing excessive heat and the engine will lose power. 

On the other hand, if there’s too much clearance between the valve and the piston at TDC (top dead center) of compression stroke, the valve will not be able to open completely for exhaust and intake

What are symptoms of valves needing adjustment?

A valve adjustment is a process of adjusting the timing, or valves, in an engine to improve its overall performance and efficiency.

Symptoms of a valve adjusting change include audible clicking or tapping noises when start crank. This stressful noise can also occurred from vacuum emissions circulators being clogged. Other symptoms include decelerating idle speed suddenly and markedly at normal engine speed for several minutes before correcting itself.

What causes valves to go out of adjustment?

There are a number of reasons why valves may go out of adjustment, including damage to the valves, related components and tight clearances.

When a valve goes out of adjustment, it can cause serious problems in your system. If you notice that your valves are not operating properly, you should immediately contact an experienced technician to fix the problem.


Lawn mower valves adjustment is a very important task, as it helps in better performance. There are signs and symptoms that you can look for to yourself whether the valves need to readjustment or not. 

Make sure you understand how to adjust the valves, and know when you should replace a faulty part. It could save you a lot of money, and more importantly, several trips around the yard. 

If you can’t solve the issue by yourself, take the lawn mower to a professional to make sure there is no further damage.

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