Choke Symbol Meaning (on or off Symbol)

New lawn mower owners might struggle to make sense of choke symbols. I remember how clueless I felt trying to figure out what these cryptic signs on the control panel meant.

So, I felt the need for creating a guideline for understanding lawn mower choke signs. A quick read should help you get familiarized with these symbols in no time.

Choke Symbol Meaning

The engine choke symbol is an icon on the lawn mower control panel that indicates whether the choke valve is open or not. When the choke valve is open, air flows into the carburetor and mixes with the fuel.

It closes when sufficient air has entered the carburetor for combustion. The symbol, therefore, indicates the current status of the choke valve situation. 

How Does Choke Work In Lawn Mowers?

Choke levers are commonly installed on small engines like the ones typically found in lawnmowers. These levers serve a vital role in regulating the airflow that enters the carburetor. By adjusting the airflow, they ensure the precise balance of fuel and air required for optimal combustion.

This balanced mixture is crucial for igniting the engine and generating high temperatures. However, in some engines, the choke lever is substituted with a primer bulb. This bulb simplifies the process by directly injecting extra fuel into the combustion chamber, thereby increasing the fuel ratio.

The choke valve, also known as the throttle, on lawnmowers gets its name from its main function. This valve effectively controls the amount of air entering the combustion chamber of the engine’s carburetor, similar to restricting or regulating the airflow.

By reducing the airflow, the fuel in the chamber can quickly heat up, speeding up the ignition process of the engine.

The engine’s internal temperature significantly impacts its ability to burn gasoline. When the engine is warmed up, the higher temperature improves the combustion process, making gasoline burn more easily and effectively.

However, during a cold start, when the metal is cool, the combustion process is hindered, resulting in less efficient utilization of fuel.

How Does The Choke Symbol Look Like?

The choke symbol on lawn mower panels might not be the same across all models. Here, I will discuss the different types of choke symbols I have seen on lawnmowers over the years. Let’s begin with the most common one.

An “O” Symbol With A Line

In most lawnmowers, you might come across a line that crosses the “O” symbol either horizontally or diagonally.

When this line is visible, it means that the choke is turned on. To deactivate the choke, simply pull the choke lever upwards or forwards until it lines up with the symbol indicating the choke is closed.

On the flip side, when the “O” symbol is accompanied by a vertical line in its center, it signifies that the choke is turned off.

To activate the choke, pull the choke lever downwards or backward until it points to the symbol indicating an open choke.  To sum up, the closed choke symbol features a vertical line and the choke open symbol has a horizontal line. 

Rabbit And Turtle

Rabbit and Turtle Choke Symbol
Rabbit and Turtle Choke Symbol (Source: Merrypad)

This is another commonly seen choke symbol in lawnmowers. The rabbit symbol denotes an open choke, allowing airflow and signifying that the engine is set for operation.

On the other hand, the turtle symbol represents a closed choke, regulating airflow to ensure a constant fuel flow for a smooth engine start.

“I” and “O” Choke Symbols

Some mowers are designed with choke symbols labeled “I” and “O” accompanied by a red or blue switch. These symbols are positioned on opposite sides of the switch, which is colored either red or blue.

When the switch is moved to the “I” position, it indicates that the choke is engaged or closed, limiting the airflow.

 To start the engine at lower temperatures, press the switch into the “I” position. When the switch is in the “O” position, it indicates that the choke is turned off or open, allowing unrestricted airflow. This position should be selected once the engine has warmed up and is ready for operation.

“Open” And “Close” Choke Symbols

This is pretty self-explanatory. The “Open” label suggests that the choke is deactivated, making it ideal for situations where maximum airflow is desired, such as when the engine is already warm or operating in optimal conditions.

On the other hand, the “Close” label indicates that the choke is activated, resulting in restricted airflow.

Choke On And Off Symbol

When the choke is set to “On,” it indicates a closed position, restricting the airflow. This setting is typically utilized when starting the engine, as it provides a richer fuel mixture necessary for a successful ignition.

On the other hand, when the choke is in the “Off” position, it means that the choke is open, allowing unrestricted airflow.

“Start” and “Closed” Choke Symbols

In this setup, selecting the “Start” position activates the choke, ensuring that it is closed to achieve the necessary fuel richness during engine start-up.

Conversely, the “Closed” label indicates that the choke is off, allowing unrestricted airflow and a leaner fuel mixture for optimal engine performance during regular operation.

“Full Choke” And “Run” Choke Symbols

If you encounter a label that says “Full Choke” on the choke control, it means the choke is in the on or closed position, enabling the regulation of airflow.

Occasionally, you may find the label simply stating “Choke,” which indicates the same function. On the flip side, when the label reads “Run,” it implies that the choke is off or open, allowing unobstructed airflow.

If you have a lawnmower with a twin-cylinder engine, you might notice a label labeled “Half Choke” positioned between the “Full Choke” and “Run” labels.

This intermediate setting indicates that the choke is partially opened or closed. It ensures that the mower continues to run smoothly when transitioning between the “Run” and “Full Choke” positions.

For a smooth adjustment to restricted airflow, move the choke lever to the “Half Choke” position. This intermediate position allows the mower’s engine to adapt gradually and avoid any abrupt changes.

Once the engine has successfully adjusted to the restricted airflow, you can then proceed to switch the lever to the “Full Choke” position to avoid engine stalling. 

This safety mechanism is more common in Stihl choke symbol systems, mainly in Stihl chainsaws. There are I and O signs for denoting stop and run symbols, respectively.

The symbol that features a slightly horizontal line between two parentheses is the half choke symbol and the one with the more horizontal line is the choke symbol.

Choke symbols in Stihl chainsaws
Choke symbols in Stihl chainsaws. The second symbol from the bottom is the half-choke symbol and the bottom one is the choke symbol (Source:

In case your mower lacks the specific “Half Choke” label, you can still prevent it from stalling out. Simply position the choke lever between the “Full Choke” and “Run” settings.

This intermediate spot ensures that your mower receives reduced airflow, allowing it to adapt smoothly without any risk of engine shutdown.

Where To Find Choke Symbols On Lawn Mowers?

The choke’s position can vary across lawnmower models, with even greater differences observed among mowers from different manufacturers.

Generally, most mowers incorporate a choke valve located on the engine body. Alternatively, some mowers are designed with a practical choke lever positioned on the handle.

Over time, locating the choke on your lawn mower can become a daunting task as dirt and debris accumulate. Luckily, certain mowers are equipped with a bulb alongside the choke symbols. If the bulb malfunctions, determining whether the choke is in the on or off position becomes problematic.

The presence of a butterfly valve in your lawnmower indicates that the choke can be found in the manifold. When trying to locate the lawnmower choke, it’s essential to distinguish between a manual or automatic choke.

For a manual choke, simply follow the cable that connects the trigger to the engine. As for an automatic choke, it is typically situated near the air intake.

Should The Choke Be Open Or Closed When Starting Lawn Mower?

When starting the engine, the choke lever stays closed to limit the airflow entering the combustion chamber. This important adjustment effectively addresses the issues related to fuel delivery and plays a significant role in swiftly bringing the engine to its necessary operating temperatures. 

The combination of the choke and spark plug is key in this process. As the spark plug ignites the gasoline, it burns at a faster rate due to the limited air supply caused by the closed choke lever. Consequently, this accelerated combustion process efficiently heats up the engine in a prompt manner.

When the air-to-fuel ratio is low, it is described as running “rich.” It indicates that there is a higher proportion of fuel compared to the available air.

In a rich fuel mixture, combustion occurs rapidly due to the restricted amount of air present for heating. The retained warm air in the combustion chamber is crucial for maintaining optimal temperatures.

As a result, the mower operates efficiently and delivers a consistent and dependable power output. 

Should You Run A Lawn Mower With The Choke On?

Once the cold engine has undergone the necessary warm-up process, typically lasting a few seconds, it becomes unnecessary to maintain the choke in the engaged position.

The primary function of the choke is to restrict the air supply during the initial start-up phase when the engine requires a richer fuel mixture for smooth operation. 

However, as the engine warms up, it becomes more efficient, and the air-to-fuel ratio needs to be adjusted accordingly.

Leaving the choke engaged beyond the warm-up period can lead to undesirable consequences. One significant effect is the continuation of a rich fuel mixture, where an excessive amount of fuel is present compared to the available air. 

This results in increased gasoline consumption within a shorter duration, as the excess fuel is burned rapidly.

Not only does this waste fuel, but it can also lead to inefficiency and potential engine issues. Moreover, the prolonged operation of the choke in the “on” position can potentially cause the engine to overheat. 

This occurs due to the rich fuel mixture generating more heat than necessary, which the engine may struggle to dissipate effectively. Engine overheating can lead to various problems, such as reduced performance, increased wear and tear, and even engine damage in severe cases.

To ensure optimal performance and avoid potential issues, it is important to turn off the choke once the engine has warmed up adequately.

This adjustment allows for a proper air-to-fuel ratio, promoting efficient combustion and minimizing excessive fuel consumption. Additionally, it helps maintain the engine’s temperature within a safe range.

Remember, understanding the appropriate usage of the choke and adjusting it accordingly contributes to the overall efficiency, longevity, and smooth operation of your engine-powered equipment.

So, I strongly advise against running a lawn mower for prolonged periods with the choke on. 

Mower Only Runs When The Choke Is On

Sometimes, you might encounter a situation where your lawnmower only runs when the choke is engaged. When you switch on the choke to start the equipment, it runs smoothly, but the moment you turn the choke off to run it normally, it shuts off. Before considering repair options, there are two factors you can examine.

One possible problem could be a blockage in either the fuel line, air filter, or fuel filter. This obstruction leads to an imbalance where there is an excess of air and insufficient fuel to sustain the machine’s operation.

If you have the necessary expertise, you can attempt to address this issue on your own. However, if you lack the skills, seek professional help. 

Inadequate fuel delivery may also stem from a tightly screwed carburetor, causing excessive fuel restriction during low-speed operation.

To resolve this, you can gently loosen the screw using a screwdriver. Try turning the screw half a turn anticlockwise and monitor if the issue improves.

Final Words

Understanding choke symbols for lawnmowers is essential for proper operation and troubleshooting.

The choke plays a crucial role in regulating the airflow and fuel mixture within the engine’s combustion chamber, especially during cold starts or when the engine is not running smoothly.

Latest posts by TAYLOR GALLA (see all)

Leave a Comment

Your email address will not be published. Required fields are marked *