You’re ready to mow your lawn, but when you pull the starter cord, all you hear is a sputtering cough. What’s going on? Maybe your lawnmower’s choke is to blame. While many homeowners know a choke is essential for starting their mower, the specifics of what it does and how it works can be confusing. This comprehensive guide will demystify the choke, explaining its purpose, how it functions, and how to troubleshoot choke-related issues. By the end, you’ll be confident in understanding and using your lawnmower’s choke to achieve smooth starts every time.
A Quick Overview of the Choke
The choke on a lawnmower is a device that temporarily enriches the fuel mixture entering the engine, making it easier to start. It achieves this by restricting airflow to the carburetor, thereby increasing the concentration of fuel in the air-fuel mixture. This richer mixture is easier to ignite, allowing the cold engine to fire up smoothly.
How Does the Choke Work?
The choke operates on a simple principle: it restricts airflow to the carburetor. This restriction causes the engine to receive a mixture of air and fuel that is richer in fuel, making it easier to start. There are two primary types of chokes used on lawnmowers:
1. Manual Chokes:
These chokes are operated by a lever or button, usually located on the carburetor or the engine housing. The lever or button directly controls a plate that partially blocks the airflow into the carburetor.
How Manual Chokes Work:
- Choke Engaged: When the choke is engaged (lever pulled or button pressed), the plate partially blocks the airflow to the carburetor. This results in a richer fuel mixture that is easier to ignite.
- Choke Disengaged: When the choke is disengaged (lever released or button depressed), the plate moves to allow more air into the carburetor, resulting in a leaner fuel mixture suitable for normal running.
2. Automatic Chokes:
Automatic chokes use a thermostat-controlled valve to regulate airflow. This valve is activated by the engine’s temperature.
How Automatic Chokes Work:
- Cold Engine: When the engine is cold, the thermostat closes the valve, restricting airflow and creating a rich fuel mixture for easy starting.
- Warming Engine: As the engine warms up, the thermostat opens the valve, allowing more air into the carburetor and gradually adjusting the fuel mixture towards a leaner ratio for normal operation.
Why Do Lawn Mowers Need a Choke?
Imagine trying to start a campfire with dry tinder. You’d need to get the right amount of air and fuel, but it’s more difficult to get a fire started with lots of air and little fuel. That’s similar to how a cold lawnmower engine works. Here’s why chokes are essential for starting a cold engine:
- Cold Fuel: Gasoline evaporates more slowly at lower temperatures, meaning less vapor is available to ignite.
- Cold Engine: The engine’s internal components are cold, meaning less air is drawn into the cylinder during the intake stroke.
To overcome these challenges, the choke is used to artificially increase the fuel concentration in the air-fuel mixture. This makes it easier for the spark plug to ignite the mixture, enabling the engine to start.
Troubleshooting Choke Issues
If your lawnmower isn’t starting smoothly, the choke may be the culprit. Here’s how to troubleshoot common choke-related problems:
1. Choke Stuck Open:
This can occur with both manual and automatic chokes. When the choke is stuck open, the engine receives a lean fuel mixture, making it difficult to start.
Troubleshooting Steps:
- Manual Chokes: Inspect the choke lever or button for any obstructions or damage. Manually engage the choke and ensure the plate is blocking airflow to the carburetor.
- Automatic Chokes: Check the thermostat for signs of damage or debris. It may need to be cleaned or replaced.
2. Choke Stuck Closed:
This usually occurs with manual chokes. When the choke is stuck closed, the engine receives a very rich fuel mixture, leading to excessive smoke and difficulty starting.
Troubleshooting Steps:
- Manual Chokes: Try manually disengaging the choke lever or button. If it’s stuck, you might need to use a small tool to help move the plate to a more open position.
3. Choke Not Working Properly:
If your choke isn’t working as it should, you may need to perform a few repairs.
Troubleshooting Steps:
- Manual Chokes: Inspect the linkage between the choke lever and the plate for damage or wear. You may need to adjust the linkage or replace worn parts.
- Automatic Chokes: Make sure the choke valve is moving freely and that the thermostat is working properly. If necessary, clean the valve or replace the thermostat.
Understanding the Choke is Key to a Smooth Start
While many homeowners might take their lawnmower’s choke for granted, it plays a crucial role in enabling a smooth start. By understanding how the choke works and how to troubleshoot common problems, you can keep your lawnmower running smoothly and efficiently. Remember: always consult your lawnmower’s manual for specific instructions and guidance on using and maintaining your choke.
This knowledge will not only help you avoid frustration on those cool mornings when your lawn needs mowing, but it will also help you extend the life of your mower by ensuring proper starting procedures. With a little understanding and maintenance, your lawnmower will start reliably for many seasons to come.
Frequently Asked Questions
What does “choke” mean on a lawnmower?
The “choke” on a lawnmower is a lever or button that restricts airflow to the carburetor. When the engine is cold, it needs a richer fuel-air mixture to start and run smoothly. The choke achieves this by partially blocking the air intake, allowing more fuel to enter the combustion chamber.
This enriched mixture helps ignite the fuel more easily and allows the engine to reach operating temperature quicker. Once the engine is warmed up, you should release the choke to allow normal airflow and prevent engine flooding.
Why do I need to use the choke on my lawnmower?
The choke is crucial for starting a cold lawnmower engine because it helps to create the ideal conditions for combustion. When the engine is cold, the fuel doesn’t vaporize as readily, making it difficult to ignite. The choke restricts airflow, creating a richer fuel-air mixture that is easier to ignite.
Think of it like starting a campfire – you need to get a good amount of fuel burning before it can sustain itself. The choke acts like the kindling that helps get the flame going. Once the engine is warmed up, the fuel vaporizes more easily, and the choke can be released.
How do I use the choke on my lawnmower?
The location and operation of the choke lever or button can vary depending on your lawnmower model. However, the general principle is the same. When starting a cold engine, push or pull the choke lever to the “choke” position. This restricts airflow and allows for a richer fuel mixture.
Once the engine starts, you can gradually release the choke lever as the engine warms up. If the engine starts to sputter or die, you may need to re-choke it briefly. You should fully release the choke once the engine is running smoothly and at operating temperature.
What happens if I don’t use the choke on my lawnmower?
Failing to use the choke on a cold lawnmower can make it difficult or impossible to start. Without the richer fuel-air mixture provided by the choke, the fuel may not ignite properly, leading to a sputtering engine or no start at all.
Additionally, not using the choke can lead to engine damage in the long run. Running a cold engine on a lean fuel mixture can cause overheating and premature wear on engine parts.
What happens if I leave the choke on too long?
Leaving the choke on for too long after the engine has warmed up can cause engine flooding. This happens when the engine receives too much fuel and not enough air, leading to a rich mixture that can’t burn properly.
You’ll notice signs of engine flooding if the engine starts to sputter, run rough, or even die completely. If you suspect your engine is flooded, you’ll need to open the choke fully and let the engine air out for a few minutes before trying to restart it.
What if my lawnmower doesn’t have a choke?
Some newer lawnmower models have automatic choke systems that eliminate the need for manual choke operation. These systems use sensors to monitor engine temperature and automatically adjust the fuel-air mixture as needed.
If your lawnmower doesn’t have a choke, you should refer to the owner’s manual for specific starting instructions. In most cases, simply turning the key or pulling the starter cord is enough to start the engine without any additional steps.
Can I damage my lawnmower by using the choke incorrectly?
While using the choke incorrectly won’t immediately damage your lawnmower, it can lead to problems over time. Leaving the choke on too long can cause engine flooding and can lead to engine damage in the long run.
Additionally, not using the choke at all when starting a cold engine can make it difficult to start and can potentially cause wear on engine components. It’s best to follow the correct procedures outlined in your lawnmower’s owner’s manual for optimal performance and longevity.