Yamaha Lawn Mower Engine Problems: Common Causes And Solutions!

Yamaha engines are known for their reliability and durability. However, like any other engine, lawn mower powered by a Yamaha has various issues with its engine. But early checking and fixing these reported issues can save you a lot and prevent further damage to your mower.  

So, what are the Yamaha lawn mower engine problems? Some of the most common problems include difficulty starting the engine, rough engine performance, overheating, and bent pushrods. And such crises are caused by various factors, including dirty carburetor, clogged air filter, faulty spark plug, and low oil levels.

If you’re experiencing issues with your mower engine, don’t let them go unaddressed. Check out our article to learn more about common problems and how to solve them effectively. Your yard (and your mower) will thank you!

Problems, Causes  & Solutions At A Glance

Here’s a table to give you a brief idea about common Yamaha lawnmower engine problems and their solutions

No.ProblemCommon CausesSolutions
1.Engine fails to startFuel issues (clogged filter, dirty carburetor, malfunctioning pump), spark plug issues (worn or fouled)Check and replace damaged or dirty fuel system components 
Check the oil level and add more if necessary 
2.Engine runs roughlyDirty/clogged air filter and carburetor problemsClean or replace the filter; adjust carburetor settings 
Clean or replace dirty carburetor parts
3.Engine overheatsLow levels of oil, cooling system issues (malfunctioning thermostat, leaking radiator)Clean, lubricate, reassemble or test the engine as necessary
Inspect and repair cooling system components
4.Bent pushrodsOver-revving, valve problems, dirt/debris, lack of lubricationRemove cylinder head inspect and replace bent pushrods
Check and swap valves 
Clean, lubricate, reassemble or test engine as necessary

Common Yamaha Lawn Mower Engine Problems, Causes and Solutions

In this section, we will discuss some common lawnmower engine problems, causes and their solutions. 

1. The Engine Fails to Start

One of the most common problems faced by owners is an engine that fails to start. There are several reasons why this may happen, but the two most common causes are fuel issues and spark plug issues.

Fuel issues

If your lawnmower engine is not getting enough fuel, it will not start. This can be caused by a clogged fuel filter, a dirty carburetor, or a malfunctioning fuel pump. 

Spark plug issues

A faulty or dirty spark plug can also prevent your lawnmower engine from starting. Over time, the spark plug may become worn or fouled, making it hard to start the engine. 


You need to fix these issues in the following way

  • You should check the fuel system components and replace any that are damaged or dirty.
  • Remove the spark plug and inspect it for wear or damage. If it is dirty or fouled, clean it with a wire brush and reinstall it. If it is damaged or worn, replace it with a new spark plug.

2. Engine Runs Roughly

Engine runs roughly can be caused by a variety of issues, but the two most common causes are a dirty or clogged air filter and carburetor problems.

Dirty or clogged air filter

If the filter is dirty or clogged, it can restrict airflow to the engine, causing it to run roughly.  This can generate more heat and cause smoke.

Carburetor problems

A faulty or dirty carburetor can also cause the engine to run roughly. The carburetor is responsible for mixing air and fuel in the correct ratio for combustion. If it is not functioning correctly, the engine may run poorly. 


Follow the following instructions to fix the common causes and prevent your engine from running roughly.

  • It’s essential to clean the air filter regularly to ensure that it continues to function correctly. Replace the filter if it’s worn according to the manufacturer’s recommendations.
  • Adjusting the carburetor settings can help resolve this issue. Consult the owner’s manual for instructions on adjusting the carburetor settings. 
  • You might also need to clean or replace the carburetor’s damaged or dirty parts.

3. Engine Overheats

Yamaha engines used in lawnmowers may also experience overheating. This can be caused by low oil levels or cooling system issues. 

Low oil levels

If the level of oil in your engine is low, it can cause the engine to overheat. This is because the oil helps to lubricate and cool the engine components. 

Cooling system issues

The cooling system in your mower engine is responsible for keeping the engine at the correct operating temperature. The engine may overheat if there is a problem with the cooling system, such as a malfunctioning thermostat of the cooling system or a leaking radiator. 


An overheating engine issue should be addressed and solved in the following way

  • You should check the amount of oil and add more if necessary. Don’t overfill as it can cause the engine to smoke.
  • Inspect the cooling system and repair any damaged or malfunctioning components. You might need to replace some components if the situation is worse.

4. Bent Pushrods

A bent pushrod can cause your engine to run poorly or not at all. The pushrod is responsible for opening and closing the engine’s valves. This allows the air and fuel mixture to enter the combustion chamber. 

If the pushrod is bent, it can cause the valve to open or close at the wrong time, which can lead to engine misfires or failure to start. Thus, bent pushrods in a lawnmower engine can be caused by several things, including


Revving the engine beyond its recommended limits can cause the pushrods to bend.

Valve problems

If the valves are not adjusted correctly or if they are damaged, they can cause the pushrods to bend.

Dirt or debris

If dirt or debris gets into the engine, it can cause the pushrods to bend.

Lack of lubrication

If the engine is not properly lubricated, the pushrods can bend due to increased friction.


To fix bent pushrods in a lawnmower engine, follow these steps:

  • Remove the cylinder head. This will give you access to the pushrods.
  • Inspect the pushrods. Look for any signs of damage or wear. If they are bent, they will need to be replaced.
  • Check the valves. Make sure the valves are adjusted correctly and are not damaged. If damaged, replace.

Test the engine. Start the engine and make sure it is running smoothly. If there are still issues, further troubleshooting may be needed.


In conclusion, maintaining a Yamaha lawnmower engine requires regular inspections, cleaning, and adjustments to prevent common problems. This includes difficulty starting, rough running, overheating, and bent pushrods. 

By addressing these issues promptly and properly, you can ensure that your lawn mower engine runs smoothly and efficiently for years to come. Always refer to the owner’s manual for specific instructions and consult a professional if necessary.

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