What Does a Lawn Mower Choke Do? Learn Its Irreplaceable Purpose

You might’ve noticed the little red button or lever on your mower, also known as a choke valve. They’re found on riding lawn mowers, rotary mowers, and more. Using the choke can save you from having to get a new mower, but how could that be possible?

A lawn mower choke reduces the airflow of the engine, allowing for more fuel to be used. This process allows the engine to spark and ignite easier, starting up in an instant. Choke valves should only be used when absolutely necessary, as they can damage the engine if they’re overused.

Throughout this post, you’ll learn all about what a lawn mower choke does, including:

• Several purposes and reason to use a lawn mower’s choke valve
• How to use a mower choke
• Quick solutions to problems with a mower choke valve

What’s the Purpose of a Lawn Mower Choke?

There’s a variety of lawn mowers, but for an internal combustion engine, the choke valve is usually located on the body of the engine or a lever on the handle. Most choke valves are butterfly valves mounted in the manifold up from the carburetor jet.

Lawn mowers are operated by using either electricity or fuel, either petrol/gasoline. For those using gasoline-powered equipment, droplets of fuel don’t evaporate well when it’s cold. In this instance, the choke has the following purposes:

• It reduces the flow of air into the carburetor’s throat, and in return, the internal pressure is reduced, and more fuel is efficiently pushed into the combustion chamber.
• The choke helps provide a richer fuel-air mixture to the engine to allow for combustion, which helps it stay running until it warms up enough for the engine to run efficiently on an open choke. This is necessary because a mower needs a rich-fuel to air mixture when starting it up cold for the first time in a while.
•  The choke valve produces a higher partial vacuum, which increases the fuel draw.
• Choke valves can increase the usefulness and overall lifespan of riding lawn mowers.

How to Use a Choke on a Lawn Mower

Manufacturers commonly use two system types to achieve smooth cold starts; the choke plate type that’s usually controlled by a lever, and the primer bulb that is simplified and easy to use. The primer bulb creates fuel-rich condition by squirting extra fuel into the engine

Here’s the procedure that should be followed when using a choke on a lawn mower:

1. Pick a suitable position to start your mower to avoid tall grass catching the blade as you try to pull start the mower. If you are using the throttle lever-type system, move the lever to full choke, but if you have the primer bulb type, press it three times.
2. The bail lever, also known as the dead man’s lever, is the bar at the top of the handlebars, usually marked with a stop symbol. It’s a safety feature, and it’s used to stop the blade from spinning and kills the engine within three seconds of bail lever activation.
3. Yank the pull cord so that the engine may produce a spark strong enough to ignite the fuel.
4. If the mower doesn’t start immediately after the first pull, give it about an hour, then try again. If it takes more than three pulls, the engine may flood, so you should give it some time. Approximately thirty minutes should be enough of a gap, but this time try it without applying the choke.
5. As soon as your engine has warmed up, move the throttle lever to fast/run if the manual choke is fitted. WikiHow suggests that if you run your warm engine while the choke is on, it’ll give off black smoke, run poorly, and probably hurt it.

What Happens if I Leave the Choke On?

Running the mower with the choke on for too long will cause black smoke, sluggish performance, and it would shorten the life of the lawn mower. The following could be reasons as to why this may happen:

• Flooding -This is a common issue associated with the choke system. Leaving the choke on after the engine has been successfully started even for a few seconds could cause too much fuel to enter into the combustion chamber. This will then cause the engine to lock up and stall. It can be quite a task to drain out the fuel out of the chamber once it is flooded. In extreme circumstances, you may need to open up the engine to drain it in order for it to start. Flooding can easily be caused by a faulty choke, like when the choke sticks or doesn’t open and close promptly.
• Clogged carburetor – If your lawnmower starts with the choke on but suddenly dies when the choke is off, it merely means that the air and fuel (which are mixed in a perfect ratio by the carburetor) aren’t working properly. eReplacement Parts points out that this is primarily caused by flooding. This is due to debris partially blocking fuel lines in the carburetor when the choke is not closing and opening correctly. The solution is to clean the carburetor or replace it. 

Maintenance Suggestions

Fixing a choke isn’t limited to experts with high-level experience and technical know-how, as many perceive. It’s not very difficult to understand, and it isn’t challenging to repair or find the problem. One only needs a few tools to be able to solve the problem in just a short time. The following are solutions for the common issues associated with the operation of a choke:

Solving the Flooding Problem: Starting the engine on the first pull of the cord is sometimes next to impossible. Instead of pulling the cord repetitively on full choke, pull it until the engine seems to be right on the cusp of starting. Move the lever to half-choke if you feel like the next pull of the cord will start the engine. This will allow some air to enter, and it will reduce the possibility of flooding the engine.

Solution for Choke Closing and Opening: According to Lawn EQ, make sure that the choke opens and closes efficiently, check and lubricate the choke shaft and the choke linkage.

You should use Gumout Carb and Choke Cleaner for a quick and easy application. Spray it on the metal surface and watch as gunk and grime slide right off. It can also be used to protect your choke shaft and carburetor to prevent them from getting clogged.

Dealing with the choke shaft to improve movement is simple; You just need to spray the shaft with the carburetor cleaner to loosen the grit. It will be knocked off during use, allowing the choke to resume working correctly.

Adjusting the Choke Linkage: If the choke linkage is not adjusted properly, it may hinder the choke’s proper opening or closing. This can be fixed by loosening the cable mounting bracket, as indicated in the equipment manual. The choke lever and cable casing can be moved to fix any gaps or problems with movement.

Final Thoughts

Lawn mower choke valves are very useful and easy to operate once you’ve given it a try. It might seem a little tricky, but it comes down to a basic lever or button.

Remember to follow the suggested step-by-step guide above to prevent flooding and smoking coming from your lawn mower. The last thing you want is a ruined mower when you need it the most!

Note: Clogged blades can be the reason that the mower doesn’t start. Review my other article more information about mower decks and how to clean them.

Here’s a rundown of the article:

• Flooding and clogs are the two most common issues to deal with when using a mower choke.
• Always give your lawn mower at least an hour to cool down if it starts to smoke.
• Never start a lawn mower in tall grass; It could prevent the engine from starting.
• If you can’t get the choke to work, try starting the mower without it.