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Your lawn mower may make a loud pop and die or won’t start because of a blown cylinder head gasket, damaged flywheel key, or gas igniting outside the engine’s combustion chamber, hindering the performance of the lawn mower.

Read until this end to uncover the most likely reasons why a lawn mower might make a loud pop and won’t start,

AND some practical tips to fix the problems to get your lawn mower working properly again.

Contents show

4 Reasons Why Your Lawn Mower May Make a Loud Pop and Die

1. Blown Cylinder Head Gasket

A blown cylinder head gasket may be one of the reasons your lawn mower makes a loud pop and won’t start. The gasket helps to separate the cylinder head from the engine block. Furthermore, it prevents oil and coolant from mixing and also seals the internal combustion process.

If the cylinder head gasket is faulty, it may cause your lawn mower to make a popping sound, preventing it from starting.

Fix: It is advisable to replace the blown cylinder head gasket with another one or better still, contact a technician to help you fix the problem.

How Do I Know if the Head Gasket is Blown?

Low Pressure

If your lawn mower isn’t starting and you do notice an oil leak, it shows that the gasket is bad. In addition, your gasket might be defective if it is not strong enough to keep the pressure of the combustion process.

Smoke From the Exhaust

This is one of the issues that you may have with the mower’s combustion system. You will observe smoke from the exhaust because oil is filling the chamber where the fuel is supposed to fire.

Leaking oil

To examine signs of oil leak from the gasket, you may notice a line of oil around where the two parts are held if it is leaking or blown.

2. Fuel Issues

If your lawn mower engine makes popping sound when you are in the middle of your mowing operation, it could be a result of fuel issues.

Low fuel pressure can make your machine backfire when there is too much air and not enough fuel in the combustion chamber. An old fuel filter or failing fuel pump can also cause a loud pop.

Fix: Adjust the speed settings of your mower by increasing the speed. This will help increase the fuel supply. In addition, replace the old filter or faulty fuel pump.

3. Sheared Flywheel

The flywheel of your lawn mower may have sheared on the mower engine.

This can make the mower make a loud bang and then stop its operation. It is important to fix this faulty component to avoid further damage to the mower.

Fix: To solve this issue, you may need to repair or replace the flywheel.

4. Problem with the Valves

Faulty valves can make your lawn mower engine shut off after making a loud pop. This problem is related to the exhaust and intake valve.

Fix: The first thing to do is to take off the valve cover and check if the valves are opening. You can also adjust the valves. In addition, set the valves between .004 and .005”.

Instances of Lawn Mower Making a Popping Sound

Now that we have discussed what can cause your mower to make a loud pop and die, it is also important to cover a few instances when your lawn mower could make a loud popping sound:

When Starting

Lawn mowers shouldn’t make a loud bang when you start them but if it makes a popping sound when you start it, something is wrong with your lawn mower.

You might have run over a large rock or other obstruction, causing the flywheel to break and fail to engage.

A lawn mower that has a broken flywheel will prevent it from starting automatically. To fix this, you need to take it to a professional for repair.

During Shut Off

When backfires occur as you are turning off the engine, the most likely issue is lowering the engine speed in a fast manner.

Moving quickly across your lawn builds up the speed of the engine and shutting off your lawn in a sudden way may cause a backfire.

The reason for this is that the engine could pump gas into the muffler where it could ignite, resulting in a loud sound

To reduce the chances of your mower making a loud pop, you need to lower the speed gradually and allow the motor to idle for fifteen seconds before you turn it off.

Furthermore, overheating can also cause this issue. If you notice this, you should contact the manufacturer about ways of increasing the airflow to the engine.

After Shut-Off

If your lawn mower makes a popping sound after you have shut off the engine, it means that there are problems with the carburetor or muffler.

You need to inspect the carburetor for incorrect settings and also check the construction of the muffler. Checking the two components will enable you to make adjustments when necessary.

Another problem that could arise is the usage of gas. A gas that contains alcohol ignites differently than non-alcohol gas, meaning that it could ignite in the muffler instead of the engine. To solve this, it is advisable to change to a low or non-alcohol gas.

Again, if your lawn mower made a loud pop when starting then do the following:

Ensure you have enough fuel in the mower
Check the air filter to ensure it is not dirty or wet from gasoline or oil
Set the valves between .004 and .005
Clean the carburetor jets

Top Recommended Handy Tools for Troubleshooting & Servicing Your Lawn Mower

Multimeter – This is useful for checking voltage, continuity & current to identify electrical problems in your mower	Filter Wrench – For loosening your mower’s filter.
Carburetor Cleaner – Choke and Throttle Body Cleaner for cleaning clogs & buildup in the fuel system.	Blade Balancer–Balances Blades After Sharpening.
Fuel Stabilizer – This stabilizes & cleans your fuel to reduce fuel system buildup	Battery Inflator – This helps to ensure your mower tires stay inflated to prevent steering or uneven cutting issues.
Socket & Allen Wrench Set – These tools are needed to service & troubleshoot your mower problems	Tachometer– Evaluates your mower’s engine performance and provides accurate data about the status of the engine
12-Volt Battery Charger – This is useful for charging your mower battery.	Lawn Mower Blade Sharpener– Adjustable Lawn Mower Blade Sharpener for Right and Left Hand Blades.