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What Happens if I Run the Lawn Mower in the Choke Position?

A choke valve is an important part of a lawn mower engine, helping to reduce the airflow of the engine. This allows for more fuel to be used, which in turn helps the engine to spark and ignite easier.

By reducing air flow, a choke valve allows for more fuel to be used, inducing a spark, and igniting easier. However, some choke valves can be too restrictive.

A proper choke valve should allow for a controlled amount of air through the engine without restricting the flow.

In this article we’ll discuss what will happen if you run your lawn mower in the choke positions. Let’s find out.

Lawn mower choke position
Lawn mower choke position

These things happens when you run your lawn mower in choke position

Running your lawnmower in the choke position will cause black smoke and it can lead to several problems such as reduced power and performance, poor fuel economy, and limited engine life.

Some engines use manual primer bulbs to start up easily. This lets you get a boost of fuel in the air mixture, which helps the engine run smoothly and gives you plenty of power right off the bat.

Oil flooding

When you have a choke system, the fuel pump will suck the air out of the engine to make it easier for combustion. Once the engine has been choked, you need to ease off on your throttle so that it can open and gather more air for combustion.

The problem is that when you run a lawn mower in the choke position, too much fuel enters the engine, and it will cause oil flooding in the combustion chamber and interfere with its operation.

This will lock the engine up and it’ll start to stall. A faulty choke will sometimes lead to oil flooding, which can be fixed by opening the engine.

When the mower’s engine is flooded with oil, you may want to open the engine cover and drain the excess oil.

There is a limit on how much fuel can be inserted into an engine, which can cause:

  1. Dilution of oil
  2. Oil will be washed from the cylinder
  3. Combustion chamber will be clogged by carbon deposits
  4. Emits a lot of smoke

This is one of many causes that leads to decline in performance.

Dirty carburetor

Dirty carburetors can cause major problems with your lawn mower engine because they block airflow, causing clogs in the fuel lines that lead into the carburetor. It can cause the engine to surge or lawn mower might loose speed.

Dirty carburetor of a lawn mower
Dirty carburetor

If an engine starts on full choke and dies suddenly when you turn off the choke, it’s likely that the air-fuel ratio is not right, and the system is not working properly.

This will lead to flooding. This is because the fuel lines are blocked, and the engine cannot get enough air to run. A good way to prevent this is to pull out the fuel lines that are partially blocked and then restart the engine when it’s clear again.

Unfortunately, this is a common problem that small engines run into. The fuel has been contaminated, most likely by a clogged carburetor.

Obstruction of gas flow can be caused by gummed up fuel filters, a clog in the fuel tank, or a faulty carburetor. If you have any one of these issues, the next steps will be to disassemble and clean your engine.

Should I run a lawn mower in a choke position?

The answer is no.

The choke is designed to restrict the amount of air that enters the engine. When you run your engine in choke position, the intake valves are closed and only a small amount of fuel is allowed into the cylinders.

It prevents huge amounts of dirt from entering and clogging up your engine. When using choke valves, only use them, when necessary, as they can cause damage to your engine if overused.

If the engine is running well in the choke position, you might need a tune up. Before you do anything, check for loose connections in the carburetor. If the air filter is a sponge type of air filter, start by rinsing it in paint thinner until it becomes clean.

If you’re having a hard time getting your engine started after you fix the clogged air filter, try taking off the carburetor. If that doesn’t work, try to buy a new one. It sounds like the engine is starving for fuel due to faults within.

Frequently asked questions

What does choking a lawn mower do?

A choke or priming bulb makes a gas engine run easily when it is cold. When the engine starts, fuel metering flows over the entire combustion chamber for optimal performance. In this case, 14.7 parts of air per one part of fuel promotes better ignition and overall performance.

How do you start a lawnmower with a choke?

If the choke is closed, to get the engine running and to start the engine, you can either push it open or pull the cord a few times. If your engine is flooded, close the choke and pull the cord a few times before starting.

What is the purpose of a choke on a carburetor?

A choke valve/cable is designed to restrict the flow of air in an engine’s carburetor, which helps increase the gas mixture and start more easily.

How do you know if your lawnmower is flooded?

If you think your lawnmower is flooded, here are some ways to check if it is true.

The first thing to do is to pull the machine out onto the lawn, give the starting cord several tugs and continue pulling until you detect a gasoline smell on your hands or clothes.


You shouldn’t run your lawn mower engine in a choke position and it is recommended to not do so. It will cause more fuel to consume, reduce the performance of the engine, emit black smoke into the air, and ultimately result in a loss of business.

If the engine runs in choke open, it might have problem with the carburetor or air filter. Try to replace those things and have a nice clean ride on your lawn with the mower you have.

But don’t, just don’t run it in choke position. It’s really a bad idea.

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