Your mower’s engine won’t start. You decide to take a look around online for a possible solution and conclude that there may be a problem with your carburetor.

Then, you realize you have another problem. You don’t understand the terms and parts associated with a carburetor. How are you going to explain or try to fix your problem?

It’s important to be familiar with the details of your equipment for the purposes of both maintenance and operation. Below, you will find a list of some of the basic terms and parts related to small engine carburetors. But first, what exactly does a carburetor do?

Put simply, a carburetor is a device that blends fuel and air into a mixture that is delivered to an internal combustion engine for energy. Such a task requires a complex series of parts and processes. To learn more about the actual operation of a carburetor, check out this article.

Without further ado, the A to Z of small engine carburetors:

A

• Accelerator Pump – Liquid gasoline is denser than air and as a result, reacts more slowly to force than air does. When the throttle is opened, airflow is faster than the flow of fuel which leads to an oversupply of air, causing an engine misfire. The accelerator pump forces extra gasoline through a jet to balance the amount of air and fuel.
• Airflow - The flow of air entering the carburetor to be mixed with fuel.
• Air-Fuel Mixture - The final product of the carburetor: a precise mixture of fuel and air that is delivered to the engine to be used for combustion.

B

• Butterfly Valve – A type of valve that regulates and controls the airflow coming into the carburetor. It can be rotated to a position that almost completely restricts all airflow, or to a position that barely blocks any airflow at all.

C

• Choke - If the engine is cold, more fuel than air is needed in the mixture to start the engine and run it until it is warm. A choke restricts the flow of air at the opening of the carburetor. This creates a stronger vacuum effect, which will pull extra fuel into the mixture.
• Cold Start - An attempt to start an engine that is cold. Cold temperatures cause fuel to vaporize less easily and condense on the walls of the intake manifold. The carburetor needs to compensate by creating a richer mixture with more fuel.
• Combustion - Burning an air-fuel mixture to create heat energy that is used to apply force to a component of the engine.

D

• Detonation - Premature ignition and explosion of the air/fuel mixture. This will interfere with the cycle of the engine and possibly even damage the engine. Also known as knocking.

E

• Engine - Machine that converts energy into mechanical energy that can power something. Internal combustion engines convert fuel into heat energy.
• Emissions - Air pollutants that introduce harmful chemicals into the environment. Many modern carburetors are required to maintain low amounts of emissions.

F

• Flooded Engine - This occurs when the air-fuel mixture given to the engine is too rich and cannot be ignited.
• Float Chamber - Also known as a bowl, this component contains an amount of fuel that is ready to be used by the carburetor.
• Fuel Pump - Replenishes the float chamber with fuel when necessary.

G

• Gas Tank - When the float chamber is reduced to a certain level of fuel, it is refilled with fuel from the main gas tank.
• Gasoline - The most common liquid fuel that is mixed with air for use in an engine.
• Gummed Up - Old gas or deteriorated metal/rubber that blocks up or obstructs the carburetor's processes.

H

• Heat Soak - Engine problems brought on by the fuel in the float chamber being exposed to excessive heat.
• Heat Deflector - These help to minimize the effect known as “heat soak”.

I

• Intake Manifold - The part of the engine that supplies the air-fuel mixture created by the carburetor to the cylinders of the engine.
• Idling - When an engine is running only to stay running, not to perform any actions.

J

• Jet - A very precisely sized opening in the fuel path that helps adjust the flow of fuel by introducing more fuel from the float chamber into the air-fuel mixture.

K

• Knocking - Also known as detonation. Premature ignition and explosion of the air/fuel mixture. This will interfere with the cycle of the engine and possibly even damage the engine.

L

• Liquid Fuel - Most commonly gasoline, this is what is stored in the float chamber and mixed with air for use in the engine.
• Lean Mixture - An imbalanced air-fuel mixture caused by an oversupply of air, which makes the engine misfire.

M

• Metering System - Ensures that an accurate amount of fuel is brought into the mixture for combustion.

N

• Needle Valve - Needle Valve – A small valve that allows flow to be precisely regulated.

O

• Open Throttle Circuit - As the throttle valve is opened more, air speed is increased in the venturi. This creates lower pressure and brings fuel into the airstream.

P

• Priming - Getting the engine ready to start.
• Piston Pump - Used to either move liquids or compress gases.

Q

• Quantity of Air-Fuel Mixture - The amount of air that enters the engine is controlled by the throttle valve.

R

• Rich Mixture - An air-fuel mixture with an abundance of fuel. This can be easier to ignite and is often necessary for cold starting. Can cause flooding.

S

• Spark Plug - A device that delivers an electric current from the ignition system to ignite the compressed mixture of fuel and air.
• Scrutinizing Spark Plugs - By removing the spark plugs, you can identify which type of mixture you have. Black and sooty plugs mean your mixture is too rich. White and light gray plugs mean you have a lean mixture.

T

• Throttle Valve - A valve at the bottom of the carburetor that, when open, allows more air and fuel to flow into the engine, and when closed, allows less air and fuel into the engine.

U

• Updraft Carburetor - A type of carburetor in which air enters from the bottom and exits out of the top, typically used with older engines.

V

• Venturi - A narrow kink in the pipe of the carburetor that causes the air flow to speed up and, as a result, a drop in pressure.
• Valve - A device that regulates and controls the flow of a liquid.
• Viscosity - How “thick” a liquid is.

Now that you know some of the basic terms associated with carburetors and engines, you’re ready to better understand carburetor maintenance and operation. If you want to know more about carburetors, check out the following:

• Carburetor problems and solutions
• How to tell if you should replace or rebuild your carburetor
• How to replace your carburetor
• How to rebuild your carburetor
• Carburetors and Parts

What is a carburetor?

A carburetor is the device(?)  inside an internal combustion engine that provides the area for air and gasoline to mix together

Components:

• Float pin
• Float bowl
• Venturi
• Choke valve
• Throttle valve
• Needle
• Main jet
• Idle jet

How a carburetor works:

• Air enters the carburetor through the engines air intake system
• How much air enters the carburetor depends on the setting of the choke, which covers the valve the more open the choke is, the more air can enter
• The air is pushed through an opening that narrows called the venturi.
• This creates a vacuum that pulls fuel in through the very small fuel jet, which lets just enough fuel in to create the right ratio for an explosion to power the engine
• Extra gas is held in the float bowl, when the bowl is full the float "floats" to the top and closes off the area that the fuel flows through,
• as the gas is released into the chamber, the float falls with the level of the gas and un-blocks the chamber opening, allowing the fuel bowl to fill back up
• When the throttle valve is open, gas is released more rapidly to make sure there is enough power to make the equipment go faster.
• When the throttle is closed and the engine is idling, there is a secondary valve called the idle valve on the outside of the throttle valve

Maintenance tips:

• Do not leave gas in your carburetor for longer than 30 days.
• Completely drain the gas tank and carburetor of fuel before storing your equipment, make sure you empty the carburetor bowl as well
• Check out Caburetor Problems and Solutions
• Find out how to tell if you need to rebuild or replace your carburetor here!
• See how to replace your carburetor
• See how to rebuild your carburetor

Featured Parts:

• Carburetors and Parts

The following is a chart of potential carburetor problems and possible remedies. This chart is intended to be a helpful guide when troubleshooting your carburetor. Each incident varies in accordance to individual use. Regular inspection of carburetor parts is recommended.

Always consult your owner's manual for specific Carburetor tuning and recommendations.

Jack's Safety Tips: Before servicing or repairing any power equipment, disconnect the spark plug and battery cables.
Remember to wear appropriate safety glasses and gloves to protect against harmful chemicals and debris. View our Disclaimer.

Featured Parts and Products:

• Carburetors & Parts
• Engine Parts
• New Small Engines

Carburetors can wear out for multiple reasons. If your engine is hesitating, stumbling, stalling, letting out black smoke, or has a hard time starting you may need to replace the carburetor. As intimidating as it may look, replacing a carburetor is an easy task that can be completed in just a few steps.

Below is a guideline to help you replace your carburetor. Be sure to check your owner's manual for specific recommendations for the power equipment you are servicing.

1. First remove the two screws holding the top of the air filter on.

2. Remove the air filter and the four bolts holding the air filter base on.

3. Remove the two bolts holding the muffler on and remove the complete muffler.

4. Remove the two screws holding the choke/throttle control on the gas tank. Move the assembly to the side.

5. Now you have access to the bolt holding the throttle linkage to the carb and the two bolts holding the carb to the engine. Remove all three.

6. Lastly remove the bolt on the bottom of the fuel tank support bracket then remove the carb and tank as an assembly.

7. Before you discard the old tank and carb be sure to remove the carb breather tube with the rubber boot and the speed set assembly from the old tank bracket. They both need to be transferred to the new assembly.

8. Install the speed set assembly on the new tank which is held on by only one screw. Then install the new carb with the new gasket onto the new fuel tank along with the breather tube and elbow from the old carb.

9. Install the new carb and tank assembly onto the engine following the opposite order that you removed them.

Jack's Safety Tips: Before servicing or repairing any power equipment, disconnect the spark plug and battery cables. Remember to wear appropriate safety glasses and gloves to protect against harmful chemicals and debris. View our Disclaimer.

Featured Parts and Products:

• New Carburetors & Parts
• Engine Parts
• New Small Engines

If your power equipment engine is hesitating to start, stalling, or eating too much gas, you may want to consider rebuilding your carburetor.

The first thing you always want to do before servicing your power equipment is check your owner's manual for specific guidelines and regulations.

Then, gather your tools, find a clean, open area and get started! Below are some helpful tips and guidelines for successfully rebuilding your carburetor.

1. Remove the carb from the engine according to your manufacturers directions. Make sure to remember where all the linkage rods and springs went.

Be careful when removing the carburetor not to tear the intake gasket. If your gasket is damaged, replace the gasket. Check out our selection of gasketshere at Jack's

2. Carefully remove the fuel bowl from the carb body, this may either be a bolt or a high speed mixture screw holding it on. Be prepared for some gas to come out of the bowl.

3. Push or pull the float hinge pin out so you can remove the float and the needle valve assembly.

4. If your carb contains an idle mixture screw, remove it along with the spring.

If your carb is equiped with a main jet that is removable you can remove and clean it. I recommend using a carb screwdriver for removal of the main jet, a regular screw driver can damage the soft brass jet.

5. Now you are ready to clean the carb with a good carb cleaner. You can soak the carb parts in cleaner for no more than 10 minutes. Then wipe them clean or blow them dry with compressed air.

Spray the carb with cleaner paying attention to all the holes. Then blow the carb out with compressed air.

Reassembly

Be careful to put everything back where it came from. If your carb has any adjustable mixture screws, when you first re-install them turn them in all the way then back out 1 to 1 and a half turns and that will get you to the point where the engine can start.

For specific tuning of your carb, consult your owner's manual.

Jack's Safety Tips: Before servicing or repairing any power equipment, disconnect the spark plug and battery cables. Remember to wear appropriate safety glasses and gloves to protect against harmful chemicals and debris. View our Disclaimer.

Featured Parts and Products:

• Carburetors & Parts
• Engine Parts
• New Small Engines