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holding small engine carburettor

How Do Small Engine Carburettors Work?

When we think about engines, we think about a complex assembly of moving parts working together.

Essentially, that’s how all engines are designed, no matter their size. And each of these parts plays a crucial role in the engine’s overall function, which is to produce movement to get some work done. That said, bigger engines have a considerably greater fuel consumption rate than smaller engines.

A carburettor is one such part that you can find inside a typical engine – big or small. You might have heard about it, but you may not know how it works. 

For this reason, we have prepared this guide, where we have discussed how small engine carburettors work. We have focused on small engines because they are the most common engine size you will encounter daily.

What Is A Carburettor?

A carburettor is present inside an internal combustion engine that provides space for the fuel and air to mix together. It is one of the most crucial components since all internal combustion engines produce energy by mixing air and fuel

So, if there are any issues with the carburettor, the engine will not start.

carberutor diagram brown

How Do Small Engine Carburettors Work?

While it may initially seem complex, the primary method in which a small engine carburettor works is relatively simple. Below, we have described the different processes for your benefit.

1. Air Intake

Air from the outside enters the carburettor chamber through the engine’s air intake system. Intake air is cleaned with an air cleaner filter hose, which filters out dust and debris.

The amount of air that enters is determined by the choke settings of the carburettor. Typically, the choke valve covers the entry to the carburettor, so the more open it is, the greater amount of air that can enter, and vice versa.

2. Mixing The Air And Fuel

After the air enters the carburettor, it is pushed through a narrow section known as the venturi. The passage of air through the narrow venturi creates a vacuum, which, in turn, pulls in a small amount of fuel from the float chamber. It is in this section that the carburettor mixes air and fuel together.

Fuel is pumped inside the carburettor chamber through a small jet needle. Once a suitable air-fuel mixture is obtained, the needle stops pumping to create controlled combustion, which, in turn, powers the engine. Likewise, the unused fuel is stored in the fuel bowl of the float chamber.

3. Fuel Flows Inside The Float Chamber

Generally, floats are used to regulate fuel levels in float chambers. If there is too much fuel, the float rises and closes the float valve to cut off the fuel line from the main fuel tank. 

Conversely, the float drops if there is not enough fuel in the chamber. If it falls below a certain level, it opens the float valve, which opens the fuel lines from the main fuel tank once more.

4. Flow Of Air-Fuel Mixture Into The Combustion Chamber

The fuel-air mixture inside the carburettor is passed through a throttle valve into the engine’s combustion chamber. In this case, the setting of the throttle valve determines how much air-fuel mixture can enter the chamber

For heavier loads or higher speeds, the throttle valve is opened fully, allowing more air-fuel mix to enter the combustion chamber, producing more energy. On the other hand, to turn off the engine, the throttle valve is closed. 

To achieve an idle speed, the flow of the fuel-air mixture is regulated through an idle valve located beside the throttle valve.

How To Clean A Small Engine Carburettor?

Now that you know how the carburettor works in small engines, you should know how to clean and maintain it. Follow the steps below to keep the carburettor and the engine in top shape for a long time.

holding small engine carburettor

Step 1: Turn Off The Fuel Valve And Air Mixture Screw

First, you must turn off the fuel inlet valve to ensure no fuel is wasted. Then you need to turn off the air mixture screws and remove the air filter panel, allowing you to dismantle the carburettor.

Step 2: Open The Carburettor And Inspect The Parts Inside

Open up the carburettor chamber by carefully dismantling the screws and nuts. If there is any excess fuel left inside, make sure to drain it away. Then inspect the choke valve, needle valve and throttle valve, along with all the other inside parts.

Step 3: Clean The Dirty Carburettor Parts

Once you have identified the dirty parts through the inspection, it’s time to clean them with a suitable carburettor cleaner. You must spray the cleaner fluid onto these parts and wipe them with a clean cloth. If there is any loose dirt, you can wipe them off with a wire brush.

Step 4: Reassemble And Test The Carburettor

After cleaning, you should replace the carburettor by reattaching the nuts and screws. Put the filter panel back in place and turn on the air mixture screw before turning on the fuel valve to test the carburettor thoroughly. Once you have ensured everything is working as expected, you can start using the machine again.

Small Engine Carburettors Vs. Regular Carburettors

A small engine carburettor has a much lower capacity than a regular carburettor because of its smaller size. You can typically find them in the engines of lawnmowers, chainsaws and tillers, while regular carburettors are used in vehicles and other heavy machinery. 

small engine carburettor silver

From a technical standpoint, however, there is no difference between a standard carburettor and a small engine carburettor since both have a similar mode of operation.

Understanding Your Small Engine Carburettor 

While many modern vehicle engines are switching to fuel injection systems, carburettors are still prevalent in older vehicles and small machines. That is why it is important to know how they work so that you can operate these machines properly.

You can fine-tune the carburettors by adjusting the valves associated with the choke and fuel filters, improving the overall engine performance. But if you maintain the carburettor properly, such adjustments might not even be necessary. 

You can’t go wrong with Manic Mechanic in Sydney when it comes to repairing, maintaining, and servicing your small engine. Our team understands small engines and can ensure your carburettor is in top condition. So, get in touch with us today to see how we can assist you.

All right, that’s it for this guide. See you in the next one!

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