Lawnmower Is Revving High – Causes & How To Fix

Close-up of a red lawnmower with a black motor, showcasing possible high revving issue.

Despite the years of service that the mower has offered, it is essential to maintain it by fixing any issues for high durability. Cases of a surging lawn mower revving that runs at high rates are common, but fortuitously, this issue is resolvable at home without paying a professional to fix it.

When a lawnmower revs high, this raises concerns as various reasons could cause this. Generally, a mower with this issue can start revving at a very high speed to the point of prevaricating itself. Usually, this can be an issue related to any part of the lawnmower.

To understand what could cause this problem, we have analyzed all the potential causes of high revving and how you can fix it at home.

The Potential Causes Of A Lawnmower Revving High

Issues With The Airflow System

Mostly a surging lawnmower may be subjected to an airflow issue. During the cutting action, the airflow assists in carrying the cut blades across the lawn; therefore, if the air holes have a blockage from debris or clogged particles, the proper oxygen flow into the combustion chamber will be disrupted, therefore causing the lawnmower to rev high.

The engine tends to suffer the most during this process.  The engine slows down when the air it requires to run blocked suddenly, and in case the particles clear. The engine will rev high as it will respond to working normally.

Such issues are quite common and can be fixed without calling a maintenance specialist.

How To Fix Airflow Issues In A Lawnmower

  • Firstly, check the air filter to confirm that debris or grass particles aren’t clogging the filter.
  • Secondly, check the vented gas cap to see what is happening because when the fuel pump pulls gas from the tank, usually, there is minimum air going in through the vented cap to replace the gas.
  • These two issues are the leading causes of airflow problems, and correcting them will fix the reduced airflow issue and get your lawnmower to work perfectly fine.

Wrong Adjustment Of The Carburetor

A carburetor usually mixes air and fuel to a ratio that supports combustion. When there is a problem with the carburetor, especially clogging of jets or incorrect adjustment, the lawnmower revs. The function of these jets is to route fuel from the end of the carburetor to the end.

They also measure the exact amount of fuel required for combustion. There are tiny openings in these jets that easily get clogged by dirt and corrosion from old fuel still in the carburetor. The main jet is also in the center of the carburetor, near the carburetor bowl.

When the main jet is blocked, the engine revs and stalls at maximum control.

How To Fix The Carburetor Issue In A Lawnmower

  • Lawnmowers have two screws; hence you can fine-tune the carburetor without the help of a repairman. One screw usually controls the idle speed, and the other modifies the idle mixture.
  • If you’re unsure of the location of the screws, the manual saves the day. Always refer to it when trying to fix your lawnmower, no matter how big or small the problem is.
  • Lastly, start the mower, let it run for a few minutes, and regulate the screws tighter or looser until the lawnmower runs well.

Old Gas Or Fuel Distresses

As the saying goes, man is prone to error. Sometimes you forget to drain your fuel tank and fill it with fresh fuel. Using old gasoline in your lawnmower could cause a variety of issues. Gasoline volatility tends to decrease over time, making it essential to replace your fuel tank with fresh fuel regularly.

In cases where the mower has last season’s fuel or contaminated fuel, a lawnmower revs high and starts generating other problems such as failure to start. Besides not running smoothly, the mower could also start sputtering in the process and eventually die out.

When the mower shows such problems, the issue is usually within its fuel system. Fortunately, diagnosing fuel problems is easy and doesn’t require a repairer.

How To Fix Fuel Problems In A Lawnmower

  • Drain old fuel from the mower and occasionally replace it with fresh fuel to enhance durability.
  • Clear out all the build-up residue that may be blocking out the engine
  • For gas-powered mowers that use a mixture of 2-cycle oil and gasoline, ensure that you’ve not poured the mix into the lawnmower carelessly.
  • Always practice regular maintenance practices: checking out the fuel system, cleaning off debris, and tightening loose screws before trying to see if the lawnmower is working again.

Problems Of A Spark Plug And Issues With The Governor Flap Assembly

The revving of a lawnmower engine is a problem that can be caused by a broken-down or wrongly adjusted spark plug. It can also be caused when a governor flap stops moving freely. Whenever a spark plug fires, it vaporizes some molecules of the spark plug cathodes.

In the long run, this crack amplifies. Thus, over time, a lawnmower fails to ignite well. Additional engine glitches might taint the spark plug and eventually break down.

How To Fix Spark Plug Problems

  • Ensure the wires of the spark plug are connected firmly.
  • Inspect the spark plug’s firing tip to check for any carbon fouling
  • Examine the porcelain casing for any cracks or chips in it.
  • Check for corrosion build-up issues inside the spark plug
  • Remove the spark plug & replace the spark plug with a new one

Simple Stages Of Replacing A Spark Plug

  • Remove all the other engine covers or heat shields parts,
  • Remove the Spark Plug Wire and replace the scraped cables with new cables
  • Doddle its Canals to remove clogged particles and other materials
  • Ensure that you have removed the shabby pad correctly
  • Ensure that the gears are clean and changed correctly.
  • Use oil and grease to prevent friction and therefore prevent another spark plug in the future
  • Finally, use manual instructions when fitting the replacement so you don’t end up misplacing or forgetting any part; everything will be as good as new.


The steps listed above will help repair a broken lawnmower, but for the best results and durable services from a mower, you should practice regular maintenance instead of waiting for something to get ruined. These include replacing the gas, tightening loose screws, cleaning the Spark Plug Threads, and lubricating them often.

All the ways to fix the causes of high revving require minimum effort as well as low operation costs. The tools for conducting repairs may require finances to purchase but will save you time and money in the long run.

You can conduct these practices at home, thus saving on the cost of hiring a professional to repair them because the practices are not demanding, and high results are guaranteed.

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