Chainsaw dnipro m carburetor adjustment. How to properly adjust a chainsaw carburetor. Fuel mixture ratio

The operation of a chainsaw engine is based on the combustion of a special mixture, which consists of fuel, oil and air. To prepare such a mixture and evenly transfer it to the combustion chamber, the engine has special device- carburetor.

The design of the saw includes a device that has factory settings. As the device is used, these settings become lost, and the carburetor must be adjusted again. To understand how to adjust a chainsaw carburetor, you need to know what parts the device consists of and how it works.

The design and principle of operation of the carburetor

Let's find out the structure of the chainsaw carburetor. This device consists of:

• housings;
• diffuser, which is located at the entrance to the device;
• jets;
• valves regulating the supply of the mixture;
• special sprayer;
• float chamber.

The device has 2 or 3 adjusting screws equipped with springs. At the end of the screws there are needle-cones.

The principle of operation of a chainsaw carburetor:

1. When the engine is turned on, the air damper opens.
2. The air moves forward and mixes with the fuel in the diffuser, where the passage narrows.
3. The air flows through the jets, then is cleaned by a filter and enters through a damper located at the diffuser inlet.
4. In this case, a special damper, which is located behind the diffuser, distributes the mixture, and it enters the combustion chamber.

The device is designed in such a way that the volume of fuel that passes through the jets is regulated by the chainsaw bolts. The volume of fuel in the chamber depends on the valve with a sharp cone. The operation of this valve is regulated by a membrane that controls the flow of mixture into the chamber. The operation of these components depends on the rotation of the internal combustion engine. The mixture is purified using a filter.

When adjustment is needed

Carburetor adjustment must be performed:

1. If the settings are lost due to loose screws or vibration, or when trying to adjust the device.
2. If the housing cover is broken.
3. To find out the reasons why the design does not work.
4. When the engine does not turn on or runs with effort, and then immediately dies out.
5. When a chainsaw shoots into the carburetor or “sneezes.”
6. The chainsaw vibrates a lot.
7. To check why there was excessive fuel consumption.
8. When thick exhaust appears.
9. If the device does not receive gasoline.
10. When the spark plugs are blackened or coated.
11. The saw cannot operate at high speeds and increase power.
12. Check the engine if it turns off when revving up.
13. The operation of the air purification units was disrupted.
14. Debris has entered the mixture distribution system.
15. The pistons have worn out.

Adjustments also need to be made when changing the brand of fuel and changes in humidity.

How to setup

Setting up a chainsaw carburetor is done as follows. Before adjusting the carburetor on a chainsaw, you should find out whether all filters are clean. The device is adjusted with three bolts:

• main jet H;
• idling L;
• idle adjustment S (some manufacturers call it LA or T).

1. The tool is installed on the workbench so that it is in a stable position.
2. The device circuit must be directed away from you.
3. There must be at least 2 m between the instrument and other objects in the room.

It is important to know how adjustments occur when the structure malfunctions. Turn on the carburetor and wait 10 minutes. The adjustment begins by finding the location of screw L at which the idle speed will be high. You need a wrench to adjust the bolts. Gradually turn the bolt, first in one direction, then in the other, until it is occupied correct position. Then turn the screw 1/8-1/4 turn counterclockwise. Then the idle speed is corrected with screw S (or T, LA).

If after tightening the needle bolt L the chain does not move, then gradually turn the screw S clockwise until the chain begins to move. Then adjust S by 1/8-1/4 turn back. If the chain moves, turn screw S counterclockwise until it tightens. Next we twist S by 1/8-1/4 turn in the same direction.

The internal combustion engine must function smoothly. You should also check how it accelerates. If you press the accelerator, the speed should increase to maximum. This means that the engine spins well.

At the end, the operation of the device is tested for Idling. When the adjustment is made correctly, the design should not work like this:

1. The chain is motionless.
2. The sound of an internal combustion engine is similar to that of a 4-stroke generator.
3. If you press the accelerator, a rapid spin will occur.

If these requirements are not met, then the idle speed must be adjusted. To do this, tighten screw S as described earlier. If this does not help, you should repeat the adjustment from the beginning.

That's what they do manual setting. Fine adjustment is carried out using a tachometer device. All actions are the same, only the screws are turned based on tachometer data. Thanks to this device, the carburetor can be adjusted faster.

Malfunctions and their elimination

Repairing a chainsaw carburetor with your own hands allows you to eliminate all problems that arise during the operation of the device.

If the internal combustion engine spins intermittently and accelerates for a long time, then you need to tighten L counterclockwise by 1/8 of a turn. Then adjust bolt S again. These adjustments should be made until the motor functions correctly and accelerates quickly.

Then check the setting of screw H. Accelerate the motor to maximum. Observe the exhaust and how the engine spins. If blue smoke comes out of it and the saw makes a loud noise, then this means that the carburetor is creating a mixture that is too rich. The highest engine speed is less than normal. Soot forms in it. In case of such a problem, you need to turn H a little clockwise. Then they control the operation of the motor and, if necessary, repeat the setting.

If the saw squeals, this means that the engine is overheating, the exhaust is crackling, and there are misfires. This means that the mixture is unsaturated, and the highest engine speeds are higher than normal. This leads to engine overheating, piston and cylinder combustion, and spark plug burnout. If this problem occurs, adjustment should be made by turning H 1/4 turn counterclockwise.

If fuel does not flow into the combustion chamber, this problem is caused by a clogged fuel filter, nozzles or device channels. To eliminate the malfunction, you will need to completely disassemble the filter and blow through these channels using a compressor. Carburetor fluid is used to clean the channels.

It happens that there is an overflow of fuel in the carburetor. This happens if the membrane has failed, dried out and become rough, and began to put pressure on the rocker arm attached to the needle. Then the needle is adjusted. To change the membrane, you need to remove the carburetor.

The motor runs intermittently and does not pick up speed well. This happens when the filter is clogged. It is necessary to remove the cover of the device and clean it using detergents.

How to remove a carburetor

Before repairing or cleaning the carburetor, it must be dismantled and disconnected from other systems. Dismantling the carburetor is carried out as follows:

1. Remove the top cover. To do this, you need to unscrew the bolts (3 pieces) that are located around the perimeter of the cover.
2. Remove the carburetor filter.
3. Then disconnect the gasoline supply hose.
4. Disconnect the motor drive traction.
5. Unscrew the cable connection end.
6. Carefully remove and pull out the gasoline supply hose.

DIY disassembly

Disassembling the Homelite chainsaw carburetor is carried out as follows. Prepare a place - a flat surface. You will need the following tools:

• set of screwdrivers and wrenches;
• detergent composition;
• ultrasonic bath for cavitation;
• a large piece of cardboard.

After you have removed the carburetor, you should disassemble it. Disassembly of the carburetor is carried out in the order provided for by the design of the device.

The device details have small sizes, so they should be folded in order, making sure that no components are lost.

After disassembly, the device is troubleshooted and non-working parts and components are replaced. Wash the device with a special liquid, dry it, and wipe with a dry cloth. Blown through compressed air tubes and jets. Before this, they are treated with ultrasound to remove plaque.

How to clean

When doing the work yourself, you need to know approximately how to clean and flush the carburetor. Wash the device as follows:

1. Unscrew the screws on the device body.
2. Open the lid and take it out small parts and lay them out on fabric.
3. The walls of the device and all parts are treated with air from the compressor.
4. If carbon deposits remain on the components, they are wiped with a degreaser.
5. The components and body are dried.
6. Assemble all the components of the carburetor and install it on the chainsaw.

It is necessary to flush the carburetor if low-quality gasoline was used to refuel it or if a chainsaw was used in severe frost. After cleaning, the engine will work better and the chainsaw will spin up faster.

Owning a chainsaw makes life easier for even an amateur in many ways, and in some professions this tool is actually indispensable. However, as any relatively complex device, the chainsaw requires periodic maintenance. Due to untimely or poor quality maintenance, as well as as a result of exposure to both planned and excessive loads, problems may appear. various kinds malfunctions. For professionals, interruptions or unstable operation of the saw reduces work efficiency or can cause a ruined workday. One of the quite common malfunctions is incorrect setting carburetor of a chainsaw, which goes astray due to unsuccessful attempts to adjust or displace the adjusting screws for other reasons.

Symptoms of malfunctions and breakdowns that require carburetor adjustment.

The following signs and malfunctions indicate the need to adjust the carburetor:

• the engine starts with effort and stalls almost instantly;
• gasoline consumption is excessively high, the exhaust is too thick, the combustible mixture in the cylinder does not burn completely;
• The factory settings of the chainsaw carburetor are lost (due to vibrations or unsuccessful attempts at adjustment);
• malfunctions of the air purification system, which led to debris particles entering the fuel mixture distributing mechanism;
• significant wear of the piston group - carburetor adjustment in this case acts as a temporary measure.

It is clear that if dirt gets into the fuel system, one setting alone will not solve the problem - it needs to be flushed. In case of wear of the piston, it is required major renovation. However, in all these cases, the carburetor is also adjusted.

Purpose, design and principle of operation of the carburetor.

A carburetor is needed to prepare the air-fuel mixture to power the engine. If the proportions in this mixture are incorrect, the operation of the motor is disrupted. If the proportion is not observed in the direction of increasing the amount of fuel, the mixture is called oversaturated, but if, on the contrary, there is little fuel, it is called lean. Both have no effect on engine operation. in the best possible way.

IN different models Chainsaw carburetors differ in design, but they are similar in principle of operation. Air flow from high speed moves along the air channel. The damper that blocks the channel allows you to change the speed of the air stream. The fuel is supplied through the atomizer into the channel, where it is mixed with the incoming air, forming an air-fuel mixture. The resulting mixture enters the engine.

Pressure in float chamber, where the fuel is located before mixing, is almost equal to atmospheric. But a vacuum is created in the air channel, due to which the fuel is drawn into the air flow. The more the damper opens, the faster the air moves, and the amount of fuel also increases - the engine speed increases. This is how you can imagine the principle of operation of a carburetor in a simplified way.

For efficient, smooth operation of the tool, obtaining maximum output and at the same time economical consumption fuel requires adjustment of the chainsaw carburetor. Before adjusting, you need to check the fuel and air filters - they must be clean. On most chainsaws, the adjustment is carried out by three screws: idle, high speed, low speed. ABOUT correct setting The carburetor is indicated by the following signs:

1. The chain does not move at idle.
2. The engine accelerates smoothly and quickly.
3. The sound of the running engine is smooth, similar to the sound of a four-stroke engine.

When adjusting the carburetor, you need to treat it with all possible care, because errors in the settings can lead to very serious consequences, including engine malfunction. If you are not 100% confident in your abilities, you need to contact a service center.

Adjusting the carburetor of the Husqvarna saw.

For the running-in mode, so that the parts receive sufficient lubrication, the carburetor of the Husqvarna chainsaw is adjusted so that the maximum speed is 600–700 rpm. below working. If it is not possible to set the operating maximum frequency using the tachometer, you should not change the preliminary settings with screw H. The manufacturer is prohibited from exceeding the maximum number of revolutions. If, after completing the adjustment, the saw chain moves when the engine is idling, turn screw T counterclockwise to force it to stop completely.

For precise adjustment, the saw must be warmed up for at least 10 minutes and placed on a flat surface. The tire should be directed in the opposite direction from the person performing the adjustment. On initial stage should be discovered highest value idle speed. To do this, screw L is smoothly turned, first from left to right, then vice versa. When the maximum speed has been found experimentally, screw L should be turned counterclockwise by a value from 1/8 to a quarter of a full turn.

The idle speed is adjusted using a jet marked with the letter T. It must be turned from left to right until the chain begins to move. Then move smoothly in the opposite direction until the chain stops rotating. Screw H is considered to be installed correctly if the noise of the saw at full throttle without load remains small. If the exhaust is too smoky and the saw makes a lot of noise, the mixture is too rich. You need to turn the jet H clockwise until the correct sound is achieved. You can see how to properly adjust the carburetor in the video below.

Chainsaws Partner and Shtil, their adjustments.

In Shtil and Partner chainsaws, adjusting screws H and L set the proportion of air and gasoline in the mixture. When the screws are loosened, the mixture becomes richer and the speed increases. Screwing leads to a leaner mixture and, accordingly, a decrease in engine speed.

Setting the carburetor of the Partner chainsaw to idle speed is carried out using screw T (Shtil marks this adjustment with the letters LA). Basic tool adjustment is done at the factory during final testing. In most cases, the carburetor is adjusted to supply a slightly richer air-fuel mixture than the optimal calculated one. The settings set by the manufacturer must be saved during the first few hours of operation, during the break-in period. After this, more fine adjustment, although this is not necessary, the saw will work fine on basic settings.

For fine adjustment of the carburetor, a tachometer is required, in addition, you will need technical documentation to carry out work in strict accordance with the manufacturer's requirements. The best solution will be entrusted with jewelry customization fuel equipment specialists.

If you still decide to adjust it yourself, you should start with screw L, then move on to jet H, after which you set the idle speed by rotating screw T (or LA - if it’s a Stihl saw).

By smoothly turning screw L in both directions, a position is sought at which the idle speed will be maximum. Once this point is found, you need to unscrew screw L 1/4 turn. If the chain continues to move while the engine is idling, screw T (LA) is slowly unscrewed until the chain stops.

After setting the maximum speed with screw H, the value of their frequency is checked using the tachometer. If the maximum rotation speed does not correspond to the values ​​​​specified in the documentation, the adjustments are repeated. If at maximum speed the mixture is too rich, too much smoke comes from the muffler; if the mixture is lean, the saw makes a squealing sound and the engine heats up excessively. The adjustment ends with setting the idle speed - the position is considered correct if the engine runs exactly at minimum speed and the chain is stationary. The idle speed setting can be seen in the video below.

Setting up the carburetor of a Chinese chainsaw

Almost any Chinese chainsaw has the same adjustments as its branded counterparts. The same screws L, H and T are present. Sometimes there are saws in which only the idle speed can be adjusted. However, according to reviews from owners and service workers, not every chainsaw can be adjusted without problems. Even for experienced repairmen, some models can take a decent amount of time before getting an acceptable result.

The standard position for “Chinese” carburetors is the position of the screw L, at which it is loosened by one and a half turns from the fully clamped position. For screw H - one revolution from the same state. In many videos, screw L is called adjusting the quality of the mixture, and screw H is its quantity. The idle speed is adjusted in the same way as described above on a warm engine.

It is rare that the owner of a private house or cottage does not have a chainsaw in his arsenal of tools. It is needed both during construction or for renovation of houses and cottages, as well as for garden care. The chainsaw does not need to be connected to an electrical outlet, but it must be refueled with gasoline, or rather, a mixture of gasoline and oil. As a rule, the following troubles can happen at the most unexpected moment:

• the chainsaw does not start;
• the engine began to work intermittently;
• stalls;
• does not develop power;
• smokes a lot.

Most often, to eliminate this kind of problem, you need to know how to adjust the carburetor on a chainsaw.

How does a carburetor work?

In order to understand how to adjust the carburetor on a chainsaw, you need to understand the operating principle of this device. An illustration will help us with this, demonstrating the processes occurring in the carburetor.

The operating principle of the main dosing system is based on comparing the pressure at the bottom (1) and at the top of the membrane (2). When the throttle valve (5) is fully opened, the piston (3) rises approximately half its stroke until the engine reaches speed. That is, when the engine speed increases, it will create additional vacuum, and the piston (3) with the needle (4) rises, thereby increasing the amount of fuel entering the engine. But the initial task of this system is to stabilize the vacuum in the needle area. This is necessary so that the fuel mixes better with air.

Now let's look at what elements the carburetor consists of.

Depending on the type of chainsaw and the manufacturer, components and their quantity may vary.

After studying the illustration, you will find out the name of this or that carburetor part.

1. Top cover mounting bolts.
2. Fuel filter.
3. Spring.
4. Branch fixing bolt.
5. Return spring for booster pump.
6. Retraction.
7. Fuel adjustment screw.
8. Screw for adjusting the quality of the gasoline-air mixture.
9. Rubber compressor.
10. Membrane.
11. Pad.
12. Gasket under the membrane.
13. Membrane.
14. Housing (installed on top of the membrane).
15. Aluminum backing plate.
16. Carburetor cover.
17. Air damper control.
18. Throttle control.
19. Carburetor body.

Causes of chainsaw malfunctions

Before you try to adjust the carburetor with your own hands, you need to find out their nature. Let's consider several standard situations:

Now a little about how to determine the cause of unstable engine operation.

When working with a chainsaw, you must follow safety precautions. The tool must be placed on a flat and stable platform. Also, don't forget to put a protective cover on the chain.

The density of water is higher than gasoline, so all of it is at the bottom of the tank. You need to turn off the fuel supply valve and unscrew the sump cap on the tap. If the valve does not have a sump, then you will have to disconnect the fuel line from the carburetor, and tilt the saw to the side drain hole in the tank, insert the hose into plastic bottle(or glass jar) and open the tap. After draining a little gasoline, the tap closes. If you can see rolling balls at the bottom, then this is water. Their absence indicates the opposite. The carburetor needs to be removed and cleaned.

Disassembling a carburetor is much easier than assembling it. Film the disassembly process and speak your actions out loud. If you don’t know where to install the part, you can watch the video.

The disassembled carburetor must be blown out with air, supplied from the compressor, and reassembled in the reverse order.

Problems with spark plugs

In order to determine the cause of the malfunction, you need to unscrew the spark plug. You can tell a lot from her condition. More details about this:

1. The spark plug is dry, but the engine does not start. No gasoline is entering the cylinder. This is a carburetor problem (or the gas has run out).
2. The candle is wet. Gasoline is supplied, but there are 2 possible reasons that the engine does not start - there is no current supplied to the spark plug or it is flooded.
3. The candle is black. This condition indicates a highly enriched gasoline mixture. Glow ignition may occur - the carbon deposits become hot and the mixture ignites even after the ignition switch is turned off. The spark plug needs to be cleaned or replaced.
4. Large gap between anode and side electrode. The main reason is an incorrectly selected candle. The anode becomes very hot and melts. The spark plug needs to be replaced.

Power supply

How to check whether current is supplied to the spark plug? The tip is removed from the candle and inserted into it new spark plug and placed on the engine housing. Turning on the ignition, you need to try to “start” the engine. If there is a powerful spark at the spark plug, then the problem is only with the old spark plug. It also happens that there is a spark, but the engine still does not start. The fact is that you can only check the performance of a spark plug under pressure in a special device.

When checking for the presence of a spark, the spark plug should never be held in your hands, since a very high voltage is applied to it.

If there is no spark, then you need to check the ignition switch by ringing its contacts. If you don't get the desired result, you can try replacing the candle holder or connecting a high-voltage wire directly to the candle. No spark? We are trying to replace the high-voltage wire (if possible). No spark again? In this case, you will have to purchase and install new sensor hall, and perhaps even an electronic ignition unit.

It is better to entrust this work to a specialist, and he will be able to say with accuracy what needs to be purchased after the audit.

Having dealt with the reasons, ignorance of which could prompt incorrect actions, we will dwell on the reasons associated with the need to adjust or repair the carburetor.

Carburetor adjustment

If none of the above malfunctions are detected, all that remains is to figure out how to adjust the chainsaw using the carburetor adjusting screws.

If gasoline with a lower octane number was poured in, you will have to increase the fuel supply, enriching the mixture, otherwise the saw will work weaker. Fuel consumption will increase and it will turn out that by purchasing cheaper gasoline, you spent more money than if you purchased good fuel.

The chainsaw carburetor is responsible for the correct supply of fuel to the combustion chamber of the engine. Both the efficiency and power of the chainsaw depend on the accuracy of its settings. Only a properly adjusted carburetor will ensure the lowest possible fuel consumption.

Almost all chainsaw carburetors are adjusted with three screws:

1. T. This screw adjusts the idle speed of the engine. Some manufacturers may use their own labeling. For example, Stihl uses S3 symbols; L.A.
2. N. A screw for controlling the main jet, which is responsible for maximum speed.
3. L. This screw is designed to control the quality of the mixture passing through the idle jet at idle speed of the engine.

Regulation rules

Often, the manufacturer indicates the parameters in the product passport basic settings carburetor If there is no such information, then the screws N And L You need to tighten it all the way, and then unscrew it one and a half turns. The final adjustment is performed on a warm engine.

The engine must be warmed up for several minutes and only then the carburetor throttle control must be released so that the engine begins to idle.

If the engine stalls, you need an idle speed adjustment screw. T turn clockwise until the operation of the unit becomes stable. The chain must remain stationary, otherwise you need to slightly unscrew the screw, slightly reducing the number of revolutions.

In order to understand what other adjustments need to be made, you need to try increasing the speed to maximum. If the engine is running well, final adjustments can be made.

Carburetor adjustment is performed on fresh gasoline and after cleaning or replacing air filter.

• The engine runs stably at idle speed. Screw L you need to tighten it up a little. This must be done until the engine speed begins to decrease. After this, the screw is unscrewed a little to stabilize engine operation.
• Now you need to listen to how the engine operates at maximum speed. The manufacturer sets its own restrictions on maximum speed rotation of the crankshaft, but it is unrealistic to check such readings without a tachometer, so you need to do this by ear. How? An ear for music is not needed here, but it is necessary to use memory, since many have heard how a chainsaw motor works in normal mode. In addition, at very high speeds, misfires may occur, so the engine will run unstably. If the speed is too high, you need to turn the screw out a little N. In order to increase the speed, the same screw must be screwed in.

Checking the correct settings

If everything is done correctly, the chainsaw will work without interruption. Evidence of this will be the following facts:

• When the engine is idling, the chain must be stationary.
• The engine runs smoothly and responds responsively to accelerator control, quickly picking up speed.

If something is wrong, then you need to start adjusting the carburetor again, using the above recommendations.

In some cases, when the carburetor fails and you cannot repair it yourself, you need to contact a specialist, since adjustments cannot correct this problem.

Video

This video shows how to adjust carburetor idle speed STIHL chainsaws MS:

Carburetor - one of the components in the fuel supply system of the engine internal combustion. It is designed to form a mixture of fuel and air with regulation of its supply to the combustion chambers. The carburetor is practically no different in functional purpose from the automobile, in principle, fuel regulation.

To begin adjusting any device, you need to know its design, operating principle and its place in general scheme power unit.

Let us recall the operating principle of an internal combustion engine:

1. A mixture of fuel and air is supplied to the cylinder.
2. The spark plug ignites the fuel.
3. The created pressure acts on the piston.
4. The reciprocating stroke of the piston through the connecting rod and crankshaft is converted into rotational movement, which is transmitted further through a system of shafts and gears.

The responsible device responsible for the composition of the mixture and its quantity is the carburetor. At optimal ratio fuel and air, the engine runs stably. If the mixture is different, then malfunctions occur, fuel consumption increases, and power decreases.

Abnormal fuel mixture:

Carburetor design:

• the central tube is intended for supplying air, forming the composition of the fuel mixture;
• the tube consists of two cones connected to each other, that is, it has a narrowing - a diffuser, through which the air flow receives an additional kinetic impulse;
• in the narrowing area there is a nozzle - a hole through which fuel is supplied;
• the volume of air supply is regulated by an air damper located across the main pipe;
• the fuel flow is regulated by the fuel needle located in the nozzle;
• fuel is supplied through a nozzle from a chamber with a float, which ensures a stable level of fuel upon entering the air chamber.

The principle of operation of the carburetor

When a gas flow moves through a diffuser, it the speed increases, and a vacuum (low pressure) occurs. In the chamber with the float, the fuel is at atmospheric pressure. Due to the difference in pressure values, the fuel rushes into the air chamber, where it mixes with air.

The volume of the supplied fuel-air mixture is regulated by the location of the air damper. With a larger opening, more fuel flows in - the engine speed increases.

Signs of unstable carburetor operation:

• increased fuel consumption;
• increased exhaust, manifested in the appearance of black smoke;
• unstable operation or engine failure immediately after starting - the fuel mixture has become lean;
• the engine does not start;
• there are interruptions in engine operation (another reason is carburetor clogging);
• wear of the piston group - repair will be required, since carburetor adjustment is a temporary measure;
• strong vibration appeared when the engine was running;
• The carburetor settings have been misadjusted.

Carburetor adjustment

The carburetor is adjusted using three screws:

• screw L is used to adjust low engine speeds;
• high speed – screw H;
• idle speed – screw T.

For reliable results when adjusting the carburetor, you must have practical experience and tachometer (a device for determining engine speed), and also know specifications saw blade (engine speed range).

Prerequisites:

The adjustment steps are as follows:

• Screw L is used first;
• next comes screw H;
• the final stage is the T screw.

Carburetor adjustment sequence:

If one of the conditions is violated, the adjustment should be repeated, excluding the main, basic stage from it. If it is impossible to independently adjust the operation of the carburetor, it is advisable to contact professional technicians.

Remember that an unregulated saw is a source of increased danger.

Video from Youtube about repairing and adjusting a chainsaw carburetor using the example of a carburetor from a Ural saw.

A chainsaw is an indispensable tool, both in household farming and on summer cottage. But even the most reliable “iron” assistant begins to mope, sometimes it won’t start, sometimes it stalls. There can be many reasons, both related to the quality of the fuel mixture and the engine.

There are a lot of nuances, we will not consider all of them in this article. Let's take a closer look at that part of the engine called the carburetor. And we will try to find the answer to the following questions: when is it necessary to adjust the carburetor of a chainsaw and, in fact, what is the scheme for such adjustment.

Chainsaw carburetor design

Before you start making adjustments, you need to know the structure and principle of operation of the carburetor. This will help avoid many “complications”. So, first, let's remember the principle of operation of an internal combustion engine. The cylinder contains fuel; when burned, it creates a small “explosion” which creates a lot of pressure. This pressure pushes the piston; the piston, when in motion, rotates the crankshaft. Ultimately, the pressure energy is converted into torque, which drives the chain through the sprocket.

At normal operation The engine burns only up to 10 milligrams of fuel in each cycle. And the fuel mixture is prepared and supplied in the carburetor.

Thus, the purpose of the carburetor is to mix the combustible mixture with air in the required proportions. If these proportions are violated, engine operation is disrupted. For example, when mixing, little fuel is supplied, but on the contrary there is a lot of air, then such a mixture is called “lean”. And vice versa, if there is not enough air, but on the contrary there is a lot of fuel, then this is a supersaturated mixture. Both cases lead to malfunctions in the normal operation of the engine and require adjustment.

The carburetor consists of the following basic elements, and although the design may differ depending on the model, the structure and principle of operation are approximately the same:

• the basis of the carburetor is a tube, its characteristics reminiscent of a wind tunnel, through which air flows; - an air damper is located across the tube; by its position, it either increases the air flow or reduces it;
• the tube has a narrowing - a diffuser, which increases the air flow speed exactly in the place where the fuel supply hole is located;
• the fuel itself in air channel enters from the atomizer, into which it enters through a nozzle from the float chamber (indicated in the photo as a fuel needle);
• the float chamber itself serves as a kind of reservoir, the purpose of which is to ensure a constant level of fuel at the entrance to the air channel.

The principle of operation of the carburetor is as follows. A fast flow of air flows through the air channel; its speed will also depend on the position of the damper. The float level provides the degree of opening of the fuel supply channel and depends on the position of the same air damper. Air flow, passing through the diffuser, picks up the incoming fuel and sprays it. At this moment, a mixture is formed, which is sucked through the intake manifold into the cylinder.

In the float chamber the pressure level is approximately equal to atmospheric pressure, but in the air channel it is rarefied. Due to the pressure difference, fuel is sucked through the nozzle into the air channel. The more the air damper is open, the greater the air flow, and, accordingly, the more fuel flows. More fuel - engine speed increases.

This is the principle of operation of a carburetor. There may be nuances in its structure, but knowing how a simple carburetor works, you can always understand and determine the purpose of other elements.

In what cases is adjustment necessary?

In general, the need to adjust the carburetor of a Stihl chainsaw, or any other brand, arises quite rarely. Signs of a misadjusted carburetor are indicated by:

1. the engine starts and stalls, or does not start - in in this case the cause may be a “poor” fuel mixture;
2. fuel consumption has increased significantly and the amount of exhaust gases has increased (fuel does not burn completely) - the cause may be a supersaturated mixture.

The adjustment itself goes wrong in very rare cases, namely:

• when the fixation of the adjusting screws was broken, there are three in total. The cause may be vibration or damage to the protective cap. This is a fairly rare case if no one touched the screws.
• in case of significant wear of the engine, namely the piston. Then the factory settings are not suitable. In this case, adjusting the carburetor of a Patriot chainsaw or another model can save the situation for a while. But here it’s time to think more about engine repairs than adjusting the carburetor of a Husqvarna chainsaw or the like;
• the reason may be due to the formation of a blockage in the carburetor, the cause may be poor quality gasoline, damage to the air filter or scale. In this option, in addition to adjustment, disassembling and washing the carburetor is necessary.

Adjusting the chainsaw carburetor

Although quite rare, carburetor adjustment may still be required. Let us immediately note that not everything can be done on your own, unless you have a tachometer and at least once see with your own eyes how to do it correctly.

To adjust the carburetor of the Makita chainsaw, like most other models, there are three adjusting screws. Although some manufacturers carefully removed two of them, leaving only one for user experimentation. So, three screws, on the carburetor body they are indicated by the following letters:

• L - this screw is used to adjust low engine speeds;
• H - high speed adjustment;
• T - for adjusting idle speed (this is left for experiments).

In general, carburetors are already adjusted by the manufacturer to optimal mode work, and the screws are designed for more precise adjustment of the carburetor of the Champion chainsaw and others, in complex climatic conditions, such as highlands, etc. Because the air is thinner there, the instrument requires more precise adjustments to operate. Under normal conditions this is not necessary.

To adjust the carburetor of a Goodluck chainsaw, as well as other brands, two screws L and H are used to create the appropriate quality of the fuel mixture. To create a lean mixture, the screws are turned clockwise, this allows you to increase the number of revolutions, i.e. Thus, they set high speeds. Accordingly, when turning the screws counterclockwise, the mixture becomes more saturated, this regulates the low number of engine speeds. Thus, when adjusting the carburetor of the Partner chainsaw, by turning the screws clockwise we increase the number of revolutions, and counterclockwise we decrease them.

Whenever adjusting the carburetor of a Chinese chainsaw or other, a number of requirements must be observed:

1. fine adjustment is always carried out when the engine is warm (engine running for at least 10 minutes);
2. The condition of the air filter must be satisfactory, i.e. clean and not clogged;
3. When rotating the chain using the adjusting screw T, it is necessary to ensure that it stops completely; to do this, the screw is turned counterclockwise.

And do not forget about our own safety, the chain must be directed in the opposite direction to us, the saw must stand securely on flat surface and do not touch any objects with the cutting part. For fine adjustment, the screws are adjusted in the following sequence L - H - T. Using screw L you need to “find” maximum amount engine speed. To do this, turn the screw clockwise, or in the opposite direction, until we “feel” for the maximum. This is where you need a tachometer, or a sensitive ear for music, and you should know the sound of the maximum engine speed; if you overdo it, especially with the H regulator, the engine will fail. Repairs will cost a pretty penny, so we strongly recommend entrusting this work to a professional.

If you have a tachometer and know the maximum number of revolutions of your engine, then you can try to complete the adjustment at your own risk. It will look something like this: find the maximum close value turns with regulator L, then return the same regulators counterclockwise by a quarter of a turn of the screw. We leave it and move on to regulator H, and if it is over-tightened, the engine will fail.

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We turn this regulator ¼ turn of the screw counterclockwise (we warm up the engine before doing this). We listen carefully or use the tachometer as a guide. If the sound is our ideal, when the engine operates at maximum, it works like a four-stroke engine. If the mixture is too rich, it makes a squealing sound. You can try to achieve an average value, not have an ideal, but remove the squealing sound with a screw. And if you are satisfied with the operation of the saw, it is better to leave it as it is, it is better than being left without an engine.

If you managed to more or less adjust the screws L and H, then all that remains is to adjust the idle speed. The ideal here is to ensure that the engine runs evenly in all positions until the chain begins to move. Rotate this screw counterclockwise until the chain stops. If this cannot be achieved, the help of a specialist is needed. An unregulated chainsaw is a very dangerous thing.

A well and correctly adjusted carburetor is:

• the chain is “standing” at idle;
• the engine accelerates quickly;
• The engine operates like a four-stroke engine.

Below is a video of adjusting the carburetor of a chainsaw