13 Carburetor Parts And Their Function (With Diagram)

Carburetor Components - The function of the carburetor is to mix air and fuel ideally at any RPM. In addition, the carburetor is also used to regulate engine RPM and generate a vacuum inside the intake.

The working principle of the carburetor is by using a vacuum or air pressure difference in two spaces. In this case, there are two core chambers namely the float chamber as a container of gasoline and venturi as a place of exit of gasoline.

Working principle, gasoline will come out automatically in the venturi when there is airflow through the venturi. That's due to the pressure inside the venturi is smaller than the float chamber pressure, according to the bernoulli law that the faster the airflow, the lower the air pressure.

However, carburetors are required to mix fuel and air ideally in any engine condition, therefore the carburetor components not only consist of venturi and float chamber. What are the components? see reviews below.

Parts Of Carburetor And Function

1. Inlet hose

This hose will deliver gasoline from the fuel lines into the float chamber. Through this channel, the gasoline from inside the tank goes into the carburetor area.

2. Needle valve

Needle valve located inside the float chamber, it can also be referred to as a gasoline valve, since the function is open and close the inlet hose. The shape of this needle is a triangle with the tip pointing into the inlet hose, the lower diameter of the needle is larger so that when the needle is pushed upwards, the gasoline line will be closed.

And consequently the gas from the inlet hose does not flow. When the needle returns down the gasoline will flow again because the channel is open.

3. Buoy

A buoy is a plastic-made component that floats on a liquid. The buoy function is to control the position of the float needle according to the volume of gasoline in the float chamber.

When the volume of gasoline is high then the buoyancy position will be higher, and this will push the needle up. However, if the volume of gasoline begins to fall then the buoy position will come back down.

4. Float chamber

This space, serves as a transit space, Because here where gasoline is accommodated to be channeled into. This reservoir holds gasoline from the fuel line at a pressure equal to atmospheric pressure.

5. Air Vent

This ventilation channel will connect the float chamber with the outside, its purpose to keep the pressure inside the float space remain stable according to the outside air pressure. Thus, the volume of gasoline coming out into the venturi becomes more ideal.

6. Main Jet

The main jet or also called main nozzle is the main channel that connects the float chamber with venturi, gasoline will come out through the main jet with the ideal volume.

The diameter of the main jet is also adjusted to the engine capacity so that the ratio of gasoline and air mixture can always be stable. Main jet, connected directly into the float space with a sloping position (lower input position) this causes gasoline does not spill into the venturi.

7. Slow Jet

Slow jet is also a gasoline output that connecting the float chamber into the intake manifold. But unlike the main jet, slow jet will flow gasoline to idle jet which is located after the throtle valve. The slow jet function is to flow gasoline when the engine is in idle speed.

8. Economizer Jet

Economizer jet works to make gasoline more homogeneous or better mixed with air. This channel is located in the middle of the idle channel. in other words, economizer jet will work when the engine is at idle speed.

9. Idle Jet

the Idle jet function is to flow air from the air filter leading directly into the intake manifold (without passing the throtle valve). It’s mean, the idle jet will play a role in idle RPM engine settings.

10. Throtle Valve

on a fixed venturi type carburetor, a throtle valve shaped like a coin. These spherical valves normally close the air ducts within the intake. When the gas pedal is pressed, the position of the valve will be more tilted so that air can flow more smoothly. From there, it can be concluded the function of the throtle valve is to regulate the speed of coming air to the engine.

11. Venturi

Venturi is a space with a narrow diameter in the intake channel. The design aims to accelerate the air flow passing through the venturi. If the airflow inside the venturi is faster, then the pressure inside the venturi will be smaller, this pressure difference makes the gasoline flow out via main jet. venturi is located before the throtle valve, so the opening angle of the valve will not make the gasoline sucked by piston suction.

12. Choke Valve

Choke valve basically has the same shape with throtle valve. The function is also the same with throtle valve, it’s close the air ducts that will enter the engine. But the choke valve is located before the venturi, so when the choke valve is closed then the piston suction will suck more gasoline from the float chamber, so the AFM (Air Fuel Mixture) can be richer. This rich mixture is used during cold start where a lot of gasoline is condensed in the intake wall.

13. Screw Control

There are two screw control on the car's carburettor, they are idle speed air screw and idle mixture air screw. The idle speed air screw will adjust the opening angle of the throtle valve in the pedal release position. With this screw, the throtle valve is not sealed at idle so that air can pass through this channel even in small volumes.

While the idle mix screw will adjust the size of the idle jet channel. This setting will affect the fuel and air mix levels, is it set with richer or leaner ?