How To Troubleshoot a Lawn Mower That Revs Up and Down?

Have you ever experienced a situation where your lawn mower suddenly started revving up and down? If yes, you might have wondered whether it is possible to troubleshoot this issue, and if possible, you must have thought about how to troubleshoot such a problem.

Firstly, gather up all the necessary tools and materials. Now, inspect the current state of the Spark plug, Fuel system, Air filter, and Fuel Filter. Next, remove the full Carburetor setup to clean, repair or replace the faulty elements and reinstall everything.

Keep reading the following article and learn details of how to troubleshoot a lawn mower that revs up and down.

What Causes the Problem?

A lawn mower might rev up and down due to faulty or blocked airflows. The most common reasons behind mower aggressive revving trouble are defective spark plugs, faulty spark plug lead, clogged air filter, and fuel filter.

Issues with fuel lines, fuel tank, wrong carburetor adjustment, or faulty internal elements of the carburetor can also cause your lawn mower to experience surging or revving problems.

However, it is hard to confirm any specific culprit without performing a thorough inspection.

Therefore, continue to check on every potential part or internal component until you reach the core of the main issue.

3 Steps to troubleshoot a Lawn Mower that revs up and down: 

When the lawn mower lacks a sustained speed due to insufficient fuel or air, it will encounter aggressive revving issues.

This mostly ends up with the mower engine shutting down abruptly while operating.

It is a common issue that most lawn mower users encounter as their mower gets older or due to a lack of regular maintenance.

As soon you encounter such commotion, you should immediately check what went wrong and fix the problem. Otherwise, this issue can eventually cause more damage to your mower.

To guide you on that task, I have prepared a quick and easy DIY method of troubleshooting a lawn mower revs up and down.

Things needed to troubleshoot a lawn mower revs up and down:

Before moving to the step-by-step troubleshooting procedures, have a proper glance at the checklist of the required tools and materials:

ToolsMaterials
Standard Mechanical tool boxNew Spark plug & lead (if needed)
Carburetor throttle body cleanerNew Air Filter (if required)
Safety Gloves & GogglesNew Fuel Filter (if necessary)
Other required internal replacement parts

Step 1- Check the Spark plug, Fuel system, Air filter & Fuel Filter:

First, check whether the gas tank is plugged or fuel has any issue. If this area has any issues fix them and if not, then move to the next part.

Check the Spark plug, Fuel system, Air filter & Fuel Filter

These two videos will guide you to troubleshoot your mower fuel system issues:

1. https://www.youtube.com/watch?v=F5vmdOH5FXg

2. https://www.youtube.com/watch?v=mJVHoN8yf6c

Next, check the current state of your spark plug and repair or replace it as required.

Check the Spark plug, Fuel system, Air filter & Fuel Filter 2

This video will guide you to check, clean, or replace the spark plug easily.

Check the Spark plug, Fuel system, Air filter & Fuel Filter 3

You should also inspect your lawn mower’s air filter and fuel filter. If necessary, replace both filters and for that, these two videos will guide you:

1. https://www.youtube.com/watch?v=yNEUv8aRgzU

2. https://www.youtube.com/watch?v=TYMfvrne8Dw

Step 2- Remove the full Carburetor setup:

You can take pictures of every single step of this particular task so that when you will reinstall everything, you will not make any mistakes.

Remove the full Carburetor setup

First start the task by removing the entire air cleaner assembly.

Remove the full Carburetor setup 2

Then, remove all the linkage cables attach to your mower’s carburetor.

Remove the full Carburetor setup 3

Next, turn off your fuel supply or drain your fuel tank.

Remove the full Carburetor setup 4

After that, remove the fuel line from the carburetor.

Remove the full Carburetor setup 5

Or, drain the gas leak from the bottom.

Remove the full Carburetor setup 6

Take these two nuts off and slide the carburetor off the main support ports.

Remove the full Carburetor setup 7

After removing the carburetor, remove the float bowl and float pin.

Remove the full Carburetor setup 8

Take the float off.

Remove the full Carburetor setup 9

Also, take the float needle valve off.

Remove the full Carburetor setup 10

You can find the main jet right inside this area where the float was.

Remove the full Carburetor setup 11

The main jet will look like the above image once it is removed.

Remove the full Carburetor setup 12

You will also find the pilot jet from the same area and remove it.

Remove the full Carburetor setup 13

Now take the emulsion tube off.

Remember, you can take off all the above-mentioned parts by using a proper sized flat headed screwdriver.

Step 3- Clean, repair or replace the faulty elements and reinstall everything:

Once you have removed the carburetor and all the connecting parts or elements, it’s time to clean every single thing thoroughly with a Carburetor throttle body cleaner.

Make sure there will not be a single hole or part of the carburetor blogged or clogged and not open.

While cleaning the entire carburetor setup, you can also inspect for the broken or severely damaged components. If required, replace the faulty parts.

After that, put everything back together as they were before and test whether your mower is still having the same problem or it’s working fine now.

If any of the above-mentioned techniques didn’t solve your issue, immediately contact the nearest dealership for professional assistance.

Warning:

Performing such repairing tasks can be hazardous. Thus, make sure you have enough knowledge and expertise to perform them. Remember to first read your mower’s instructions manual before operating, servicing, or troubleshooting it.

Frequently Asked Questions: Lawn mower revs up and down

What causes a lawn mower to pulsate?

If your lawn mower has suddenly started to pulsate, the most common reason behind this commotion can be a clogged fuel supply, bad/old gas, defective spark plug, or faulty carburetor.

What causes a lawn mower rev to bounce aggressively?

Due to an automatic transmission leak or fluid levels falling, your lawn mower rev can bounce like that.

What causes a lawn mower engine to idle up and down?

The most obvious culprit for causing such trouble is a bad idle air control valve. But to confirm the issue, check the engine light first.

What causes a lawn mower RPM to shake or vibrate?

Such a commotion can arise due to faulty spark plugs, poor fuel pressure, internal ignition misfires, or faulty idle air control valves.

What caused my lawn mower engine to shake at idle?

Weak or broken mounts on the lawn mower engine can cause such trouble.

Final Verdict

If you ever experience similar issues while operating your lawn mower, try the above fixing tricks. 

Initially, those techniques might seem a bit complicated to perform, but if you have minimum mechanical expertise and follow the steps thoroughly, you can easily get rid of this issue in no time. 

If you want the best result, you have to thoroughly follow all the instructions for troubleshooting a lawn mower that revs up and down without skipping any detail. So, keep that in your mind.

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