How to Change a Lawn Mower Spark Arrestor

Does your lawn mower engine lack power, or is it hard to start? Well, both of these issues could mean you have a clogged spark arrestor. This tiny piece of metal mesh can be enough to cause your lawn mower to sputter, which will definitely take all the fun out of mowing. So if you are having issues with your lawn mower engine, then it’s worth checking the spark arrestor. I’ll go over all you need to know about your lawn mower spark arrestor.

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How to Change a Lawn Mower Spark Arrestor (Overview)

The first step to replace a lawn mower’s spark arrestor is to remove the existing one from the exhaust pipe. The removal method depends on the arrestor’s design. So, remove the stub or flat mesh arrestor using the appropriate method and tool. Once removed, install the replacement spark arrestor to finish the process.

What Does a Spark Arrestor Do on a Lawn Mower?

What is a lawn mower spark arrestor? Well, a spark arrestor is typically a small mesh covering a muffler’s exit to catch any hot carbon embers or sparks. The idea behind a spark arrestor is to extinguish any potentially hazardous embers and sparks before they can ignite any potentially flammable material within reach. Initially, the forest service mandated the installation of spark arrestors on chainsaws to reduce the number of unintentional fires. Consequently, you’ll now find spark arrestors on all compliant small engine machines, including lawnmowers within the USA and worldwide.

Are Spark Arrestors Necessary?

A spark arrestor is not necessary to make a lawn mower run. Therefore if you remove a perfectly working spark arrestor from your lawn mower, you won’t see any difference in performance. However, a spark arrestor is a U.S. federal mandatory requirement, and you must have one installed on your lawn mower. So is a spark arrestor necessary? By law, yes.

Symptoms of a Bad Spark Arrestor

How do you tell if your lawn mower’s spark arrestor needs to be cleaned or replaced? Well, a clogged spark arrestor will restrict the exhaust gases exiting the mower muffler. In other words, your lawn mower’s engine will suffocate.

Here are some telltale signs that a spark arrestor needs to be either cleaned or replaced.

The engine won’t reach full RPM
There will be a lack of engine power
The engine will make a sputtering sound
The engine will likely stall
The engine will be hard to start

What Clogs a Spark Arrestor?

The main thing to clog up a spark arrestor is carbon deposits from the burned gasoline. In other words, the black substance you see smoking from your lawn mower’s exhaust pipe. If you have a 2-cycle lawn mower, you’ll also have burned and unburned oil deposits. So if your fuel-to-oil 2-cycle mix is slightly off, then any unburned oil will collect in the spark arrestor. To restore a spark arrestor, you’ll need to clean off the deposits or replace the spark arrestor completely.

Where is a Spark Arrestor Located?

Regardless of which type of spark arrestor your lawn mower uses, it will always be on or in your lawn mower’s muffler. For example, a stub spark arrestor is directly screwed into the exit of a muffle, whereas a flat mesh spark arrestor is covered with a plate on the side of the muffler.

How do you know where your specific design of spark arrestor is? Well, look down the muffle’s exit for a mesh, or look for the cover plate. Typically a cover plate style arrestor will have a plate attached to the side of the muffler, secured with two screws. Whereas the stub arrestor screwed into the muffler’s exit pipe is typically shaped like a socket wrench or has a side-mounted screw keeping it in place.

How to Change Lawn Mower’s Spark Arrestor (Step-By-Step)

Now let’s go over how to install a new or cleaned spark arrestor on your gas-powered lawn mower. Here are the steps for both designs: the stub and flat plate spark arrestors.