Chainsaw carburetor - device, do-it-yourself adjustment

A chainsaw is needed in construction, gardening, and landscaping - its presence greatly simplifies the performance of a number of wood processing tasks. The main component of this tool is the engine, the operation of which largely depends on the condition and settings of the carburetor. This is where the fuel mixture is prepared. This means that if the saw does not start, stalls, or does not provide the required power, it is likely that the reason for this is improper operation of the carburetor. Fortunately, in many cases you can deal with this on your own. Only for this you need to know and understand the structure and operating principle of this unit and, of course, the chainsaw itself.

2 Why is primary adjustment needed?
3 How to recognize carburetor failures?
4 Do-it-yourself disassembly: nothing complicated
4.1 Disassembling the chainsaw carburetor in the photo

5 Carburetor settings: main points

6 Repair and adjustment of a chainsaw carburetor in detail on the video

The design of a chainsaw carburetor is simple and accessible

As with other chainsaw components, before repairing the carburetor, you should study its design in detail. This will help determine the true breakdown and quickly fix it. The design of a chainsaw carburetor consists of the following elements:

Tube - equipped with a transverse damper that regulates the entry of air into the system;
Diffuser – located next to the fuel inlet. As the diffuser narrows, the air flow rate into the system increases;
Fuel needle - serves to distribute fuel;
Float chamber - regulates the fuel level at the point of entry into the channel.

To better understand the design of the unit, you will need a diagram of a chainsaw carburetor. It clearly demonstrates the location and method of connecting the main elements of the unit.

The operating principle of a chainsaw carburetor is quite simple. The needle sprays fuel into the float chamber, after which the fuel is mixed with air. Next, the finished mixture enters the engine cylinder. The more fuel supplied to the engine, the higher the engine speed.

Regardless of the manufacturer and model of the chainsaw, each of the modern tools is equipped with carburetors that have an almost identical design and operate on the same principle. The main differences lie in the materials of the spare parts and their location in the carburetor structure.

What is a fuel pump? Principle of operation

The fuel pump is designed to supply fuel from the tank to the car engine. The main task is to deliver fuel at a certain pressure necessary for engine operation.

In this article we will tell you what a car fuel pump is, how it works and find out the difference between a mechanical and electric fuel pump.

What is a fuel pump?

Fuel pump - supplies fuel to the engine. It is needed because the engine and gas tank are at opposite ends of the car.

in modern cars : mechanical and electric. Mechanical fuel pumps are usually used in carburetor-type cars, where fuel is supplied to the carburetor under low pressure, and electric ones are used in injection-type fuel systems with fuel supplied under pressure.

Mechanical fuel pumps are mounted on the outside of the fuel tank, and electric fuel pumps are mounted on the inside of the fuel tank. And some engines have two fuel pumps: one that operates at high volumes, at low pressure, inside the fuel tank, and one that operates at low volumes, at high pressure, on or near the engine.

Mechanical fuel pumps work on the principle of sucking fuel from the fuel tank into the engine. The distance between the carburetor and the pump is small, so they can operate under low pressure.

The design of the car's power system and the operation of the fuel pump
Electric fuel pumps seem to push fuel into the engine. The operation of the electric fuel pump is controlled by the vehicle's electronic system, which takes into account throttle position, air-to-fuel ratio and exhaust emissions.

Since electric fuel pumps operate under pressure, they are quite noisy and heat up quickly. It is for this reason that they are placed in the fuel tank - the fuel cools the fuel pump and muffles noise.

How does a fuel pump work?

Gasoline pumps are started by an electric motor. When you turn the ignition switch on, the on-board computer gives a signal to start the fuel pump. An electric charge is supplied to the fuel pump. The motor inside the fuel pump begins to rotate within a few seconds and creates pressure in the fuel system.

If after two seconds the computer does not receive a signal that the engine is running, the fuel pump automatically turns off for safety reasons.
It is in the first two seconds after starting the engine that you can hear the fuel pump running.
Next, the fuel is sucked into the fuel pump through a tube and leaves the fuel pump through a one-way valve, enters the fuel filter, which traps dirt and debris and then goes into the engine. The fuel pump runs as long as the engine is running.

Most often, the fuel pump breaks down prematurely for two reasons: dirty fuel filters and the habit of driving on an empty tank. In both cases, the fuel pump works to the limit, exhausting its life much faster than it was intended by the design engineers. Therefore, do not be lazy to change fuel filters, especially if the quality of the fuel leaves much to be desired.

Adjusting a chainsaw carburetor - when is the procedure required?

Often chainsaw owners think about why the chainsaw shoots into the carburetor, or why gasoline does not flow into the chainsaw carburetor? In both cases, the cause of the malfunction lies in a failure of the unit’s factory settings, and to eliminate the breakdown, the chainsaw’s carburetor must be adjusted. A number of other signs will help you understand that the chainsaw carburetor needs to be adjusted:

The engine does not start at all, or stalls immediately after starting - the reason for this may be a shortage of fuel coupled with an excess of air;
Increased fuel consumption - in this case, the amount of exhaust gases rapidly increases. The reason for this situation should be sought in an increase in the amount of fuel and a decrease in the amount of air;

There are also a number of mechanical reasons that lead to the need to adjust the carburetor. These include:

Strong vibration - it leads to damage to the protective cap, resulting in loss of fixation of all three adjusting screws;
Wear of the piston part of the engine - in such a situation, adjusting the carburetor will only temporarily prolong the operation of the tool. To completely eliminate the problem, you will have to completely replace the piston group;
The formation of blockages - they appear as a result of the use of low-quality gasoline, damage to the filter or scale. In such cases, it will be necessary to dismantle, disassemble and clean the carburetor.

In any of the above cases, it is better not to delay the procedure for adjusting or flushing the unit. Otherwise, this will lead to damage to other equally important elements of the chainsaw.

Situations in which adjustment is necessary

New chainsaws are supplied by the manufacturer with already adjusted carburetors. This is called standard adjustment. But for the normal running-in process, it is necessary to reduce the maximum engine speed and adjust the carburetor. After break-in, the chainsaw needs fine tuning to achieve maximum engine efficiency.

If there is too much fuel in the mixture, engine parts are poorly lubricated and premature wear occurs. Also, a poor quality mixture can cause the engine to jam due to overheating (this is one of the reasons why the chainsaw will not start).

This is what a jammed, overheated piston looks like from a disassembled chainsaw with an incorrectly configured carburetor.

Adjustment is necessary when the engine does not idle, stalls, or does not develop full power. Carburetor adjustment should be carried out with clean air and fuel filters. We also recommend reading an interesting article that details the main reasons why a chainsaw starts and immediately stalls.

How to properly adjust the carburetor on a chainsaw?

Before adjusting the carburetor on your chainsaw, you will need to learn the meaning of the three screws required for adjustment. These screws have certain markings and names:

Screw “L” is necessary to adjust low speed;
Screw “H” is required when tuning the motor to operate at high speeds;
Screw "T" is needed to adjust the idle speed.

It is worth noting that some chainsaws are equipped with only one “T” screw, so the carburetors of such models are adjusted by manipulating only this screw.

No matter how many screws there are on the chainsaw, the factory carburetor settings are the most optimal for its operation. The screws themselves are initially used to configure the chainsaw to work in certain weather conditions.

The carburetors of chainsaws with three screws should be adjusted using screws “L” and “H”. To increase the speed, they should be turned clockwise. In order to lower the speed, the screws turn against it. To adjust the carburetor, you will need a special screwdriver for adjustment - it will not slip off the screws and damage the threads on their “caps”.

The carburetor adjustment process consists of two stages: initial and main. The adjustment algorithm is as follows:

During the first stage, screws “L” and “H” must be tightened clockwise to the very end;
After this, these screws need to be turned 1.5 turns in the opposite direction;
At the second stage, you need to start the chainsaw and leave it for 10 minutes to completely warm up;
Then start turning the screw “T” until the chainsaw motor starts to run stably and the chain on the bar does not rotate.

Do not rush when adjusting the chainsaw. It must be remembered that the slower you turn the screws, the better you will feel the changes in the operation of the tool’s engine.

Operating principle of an internal combustion engine

The operating principle of a gasoline engine is to burn a compressed mixture of air and gasoline in a combustion chamber.

The main elements of any internal combustion engine (abbreviated as ICE): a cylinder in which the piston moves up and down under the pressure of the combustion products of the fuel mixture, and a crank mechanism that converts the reciprocating movement of the piston into the rotational movement of the crankshaft.

There are four cycles of engine operation:

fuel mixture inlet;
compression;
working stroke;
release of combustion products.

During the intake stroke, the piston moves down, creating a vacuum in the cylinder, and, like a pump, sucks the fuel mixture inside.

During the compression stroke, the piston moves upward, compressing the intake mixture.

When the piston reaches the top point, the mixture is compressed to its maximum. At this moment it is ignited by an electric spark. The compressed mixture burns very quickly, almost instantly. Something like an explosion of the fuel mixture occurs. This explosion pushes the piston down and the engine begins to operate.

During the working stroke, the piston moves from the top to the bottom, pushing the crankshaft and doing useful work.

During the exhaust stroke, the piston moves upward, pushing the spent combustion products out of the cylinder into the atmosphere. Exhaust occurs.

Then everything repeats all over again.

How to check a chainsaw carburetor?

After adjustment, you need to check the acceleration, maximum speed and engine idle. While checking the first parameter, you should sharply press the gas trigger. If the motor does not begin to gain speed, then you need to turn screw “L” counterclockwise. In this case, one turn should not exceed 1/8 of the full circle of the screw.

To measure the maximum revolutions, you will need to engage the “H” screw. To increase the maximum number of revolutions, the screw is turned clockwise. To reduce the indicator, the screw must be turned in the opposite direction. It should be remembered that the maximum speed should not exceed 15 thousand.

For a final check of the chainsaw while idling, you need to start the tool and place it on a level place. Let the engine warm up and pay attention to the following elements of the chainsaw:

The chain should not move;
Engine - when you press the gas trigger, it should confidently gain speed until the set maximum limit is reached.

An important tip is that if the carburetor is configured correctly, the sound of the chainsaw engine will closely resemble the sound of a 4-stroke engine.

The carburetor of a Chinese chainsaw is adjusted and checked in a similar manner. The only difference is that the process of setting up such tools can take much longer - on average, about an hour. In addition, it should be remembered that adjustment of Chinese chainsaws is required much more often - it often needs to be done immediately after running in a new tool.

Spare parts for chainsaw repairs

Our store offers a wide range of accessories for chainsaws from manufacturers such as Husqvarna, Oleo Mac, Stihl and Makita. Highly qualified consultants will help you understand the variety of modern chainsaws.

If you like to understand the equipment on your own, then you should pay attention to the wide selection of basic spare parts that will allow you to repair your chainsaw without resorting to the services of a paid technician.

How to remove a carburetor from a chainsaw?

Before cleaning the carburetor or repairing it, this element of the chainsaw will need to be dismantled and disconnected from other components. To do this, you must follow a certain procedure. The dismantling algorithm looks like this:

First, remove the top cover by unscrewing the 3 bolts around its perimeter;
Remove the filter shaped like a foam pad;
Disconnect the fuel supply hose;
Remove the drive rod;
Disconnect the cable end;
Carefully remove and completely pull out the fuel supply hose.

Try to perform each action as carefully as possible. Otherwise, there will be a risk of damage to important elements of the chainsaw.

Step-by-step disassembly instructions

The carburetor design of models of different brands is almost the same, so let’s take the Partner chainsaw as an example. We carefully remove each element and place it in order to make it easier to assemble later.

How to clean the carburetor on a chainsaw?

It is necessary to flush the carburetor of a chainsaw in cases where low-quality fuel is used to refuel the tool, or the tool is used at extremely low temperatures. During the work, you need to try not to damage or lose small parts of the assembly. Cleaning the carburetor is performed in the following order:

Remove the screws holding the carburetor body;
Open the lid, remove the small parts of the assembly and place them on a towel;
Carefully treat the walls of the case and all existing parts with compressed air from a can;
If carbon deposits remain on the parts, wipe them with a rag moistened with a degreaser;
Dry the body and parts;
Assemble and install the carburetor on the chainsaw.

After cleaning the carburetor with your own hands, you will notice that the chainsaw motor will work much more stable and gain speed much faster.

Why is there no gas flowing into the chainsaw?

According to reviews from owners of Chinese chainsaws, the equipment breaks down quite often and the breakdown is accompanied by a lack of fuel supply to the carburetor. If you have applied the above tips, you need to diagnose the following elements:

Carburetor needle. On cheap chainsaws, the needle in the carburetor often gets stuck, which prevents fuel from flowing. Sometimes all you need to do is move the needle and get it positioned correctly.

Oil seals. Chinese and even branded chainsaws may have low-quality oil seals with poor sealing. Fuel stops flowing when the fuel mixture begins to squeeze out through the seals. Gasoline leakage is quite possible through the seals.

Breather check

It is the breather that plays a serious role when starting a chainsaw; you can find such a part near the gas tank cap, or rather in the area of the air hole. The breather performs a simple but important role - it prevents fuel from leaking and establishes the correct air pressure. It is thanks to this air that fuel enters the carburetor, and a malfunction of this element is a common reason when fuel does not enter the chainsaw. A malfunctioning breather will create negative pressure, which will prevent gasoline from flowing to the carburetor when you try to start the tool.

Checking the functionality of the breather is quite simple; disconnect the gasoline pipe from the carburetor and check how the fuel flows. If gasoline flows in a small stream, everything is in order, if it does not flow at all, the breather is most likely clogged with dirt. If done correctly, you can clean the part, sometimes it’s easier to replace it with a new one. The cleaning procedure is performed either manually or by applying a strong jet of compressed air.

Video

Why is there no gas flowing into the chainsaw?

Breather check

Video

Preparing for adjustment

Once you know the principle of operation of the chainsaw carburetor, you can adjust it. For correct adjustment, you will need a technical passport, where you can familiarize yourself with the angles of rotation of the adjusting screws. You will definitely need a screwdriver. You can take a special one designed for adjustment, or a regular one.

The tool is installed on a flat surface. It could be a table. The equipment must be positioned so that the saw bar points in the opposite direction. The engine must first be turned off. Using a screwdriver or wrench, you need to unscrew the fastener that holds the housing cover. It must be removed to allow access to the carburetor.

Now you can remove the air filter that covers the unit you need. Sometimes a shock-absorbing foam insert is installed on top. It should also be removed. Now you can do the setup itself. The screws should be turned carefully so as not to break them. The first to be adjusted are screws L and H, which are unscrewed one and a half turns.