DIY carburetor trimmer repair

In detail: DIY carburetor trimmer repair from a real master for the site my.housecope.com.

Very often, complaints from owners of gasoline trimmers are associated with various kinds of carburetor malfunctions. Of course, in this case, it is best to seek help from specialists in this field, for whom the repair of carburetors of gasoline trimmers is an integral part of the profession. However, if you are still familiar with the basic principles of the trimmer carburetor, you can try to figure out the problem yourself, so as not to overpay money in the service, since sometimes the breakdown can be really frivolous.

This article is just intended to help you deal with the problem.

Next, we will analyze the most common breakdowns and the reasons for their occurrence.

The first step is to generally inspect the carburetor and find out if there is any fuel leakage.

If it turns out that there are no problems with fuel, it is necessary to remove the carburetor from the engine and check the condition of the gasket located next to the carburetor.

If no malfunctions are observed here, you can try to check the carburetor for tightness.

To do this, you can purchase a special device, which is part of the tool kits for repairing the carburetor repair of mowers and representing a special pressure gauge that, in fact, checks the tightness.

If you don't want to spend money on its purchase, you can use a conventional medical tonometer, on which you just need to change the pressure gauge.

When using this device, pay attention to the indication.

Video (click to play).

If the pressure does not drop and remains the same for a long time, you can rest assured, as this indicates the tightness of the carburetor.

If the pressure begins to decrease after a certain time, then there are still problems.

They can be associated with damage to any parts of the carburetor.

Before running to the nearest repair shop or specialty store selling trimers and spare parts, try to figure out the problem yourself. Sorry for the banality, but the brushcutter carburetor is not a spaceship of an extraterrestrial civilization, and it is quite possible to repair it with your own hands. To be confident in your actions, read the step-by-step instructions provided in this article.

A visual inspection of the carburetor will help detect fuel leakage and air leakage, but the main reasons for the failure of the device lie inside. Therefore, in order to determine and most importantly fix the breakdown, the carburetor must be disassembled.

It does not take much effort to disassemble the carburetor of the brushcutter.

It is enough to unscrew four screws on one side

and two on the other. This can be done using a regular Phillips screwdriver. Unscrew the screws carefully and fold them to the side. They may be needed during assembly. It is advisable to cover the table with a white cloth before disassembling so that you can see everything, even the smallest details that may fall out during disassembly.

We start disassembling from the side of the fuel supply system.

We remove the primer - a pumping bubble, which is remarkable, it is simply impossible to install the carburetor parts incorrectly during assembly. Products have characteristic ebb and flow.

Now we remove the membrane. It is she who performs the function of pumping fuel into the carburetor.

When the membrane vibrates, the other side exerts pressure on the rocker of the mechanism and the needle rises, which, in turn, opens the hole and fuel is supplied.

Remove the carburetor cover with the injection mechanism.

Further, another membrane is installed. We carefully remove it.

There is another gasket under the membrane. We also carefully remove it, without damaging it in any way.

Next, we move on to dismantling the parts from the back of the carburetor. As mentioned earlier, we unscrew the two bolts. This is already an air supply system.

A valve is located here, which, when gas is added, opens and increases the flow of air into the engine.

After removing it, a bare body remains in the hands. The carburetor is disassembled.

Identification of faults and their elimination

Now it is worth paying attention to the problems that occur during the operation of the carburetor and how to fix them.

The first thing that happens is that the holes and jets in the fuel supply system are clogged with dirt. Filters installed in the tank and directly in the carburetor do not help. They still allow small particles to pass through, which cause brushcutter failure.

Now we need to get the needle.

To do this, unscrew the bolt on the mechanism, holding it with your finger. The fact is, there is a spring there and a careless action will lead to the fact that it is lost.

We take out the needle, see photo and spring.

How to purge. The most effective way is to use an ultrasonic bath.

It is filled with either a special liquid or gasoline, a carburetor is placed there and under the action of ultrasound, the so-called cavitation effect, the channels are cleaned of contamination.

The second option for cleaning is compressed air.

You can use the compressor available on the farm and clean the carburetor channels. However, this method is effective if the contamination is not very large.

If there is neither an ultrasonic bath nor a compressor at hand, then cleaning can be done in the third way using a special cylinder for cleaning the carburetor. They are sold in almost all car dealerships and supermarkets. The price is not high and is about $ 2-3. Enough of such a cylinder for 4 or 5 purges.

Now we need to blow through the channels in the body and carburetor cover. See photo.

Another particle of dirt can get stuck under the needle. See photo. This will also lead to brushcutter failure.

Important! When cleaning the carburetor, never use needles, pins or wires. Even the slightest scratch will damage the carburetor. It will have to be changed entirely.

It is located on the carburetor cover and is a fine metal mesh. Its pollution occurs very often. This is due to the deposition of oil, additives, dirt on it.

Sometimes, when disassembling on the nets, a certain film is found. Therefore, the carburetor does not have enough fuel and the brushcutter either does not start or works intermittently. The cleaning methods are identical to the first reason: an ultrasonic bath, a compressor or a spray bottle with a special solution. In addition, if the mesh is clogged thoroughly, you need to take a soft brush for watercolors, soak it in gasoline and rinse it gently without damaging it.

They have the ability to wear out during operation. From prolonged use, they deform, stretch, lose elasticity, low-quality fuel corrodes them, and can no longer perform their functions well. This also applies to the needle itself. The fact is that it is covered with a thin layer of rubber, which wears out during operation and can no longer fit tightly into the hole. The brushcutter starts to work intermittently. To eliminate such a breakdown, it is necessary to replace all worn out parts. Where can I get them?

In specialized gardening equipment stores, a carburetor kit for a brush cutter of a certain model is sold.The cost of such a repair kit ranges from 40 to 60 hryvnia.

It includes two diaphragms, a gasket, a needle valve and a spring.

All wear parts of the carburetor can be replaced. Therefore, you should not rush and buy a new one, and you do not need to run to the workshop either, repairs are within the power of any brushcutter user. Professionals claim that the quality of the components in the repair kit even exceeds the characteristics of the native carburetor parts. Therefore, a well-repaired unit will perform better than a new one.

In addition, the bubble button for manual fuel pumping may fail. The effect of gasoline on it leads to the fact that during prolonged operation, the rubber corrodes and it begins to stick together or, under the influence of low temperatures, for example, during storage, it bursts. The button should also be replaced if necessary. In addition, its cost is small and will not affect the size of the repair budget in any way.

Based on the foregoing, it can be concluded that there are only three main carburetor malfunctions: clogging of channels, contamination of the fine filter and failure of components. In the first two cases, cleaning is enough, and in the third, a repair kit will help.

Assembling a brushcutter carburetor is a snap. All actions must be performed in reverse order:

Install a spring and a needle valve in the carburetor cover. Hold the spring with your finger and tighten the mounting bolt.

Screw the shutter of the air supply system to the product body with two screws.

Turn the carburetor over and go to the fuel system assembly. First you need to put the gasket.

Install the carburetor cover.

Install the main diaphragm.

Install the plate with the manual fuel pumping button and tighten the four screws.

The carburetor is assembled and ready for further use.

For the first time, repairing a brushcutter carburetor may seem like a complicated process, but if you have to disassemble it a second time, then this procedure will not cause much difficulty.

If you did not find any of the listed problems in your carburetor, it is recommended to contact a specialized service for help.

Modern technologies and equipment make it possible to produce the best and optimal technical solutions that become effective assistants in the arrangement of a summer cottage or a personal plot. The green lawn and other plantings can grow rapidly, a petrol cutter is used to tidy up the local area and mow the lawns, which is also called a brushcutter or trimmer, a petrol mower.

Traditional braids are inconvenient and unsafe to use, require a significant investment of time and effort, which will help save gas mowers, combining functionality and practicality in their design. In the photo of the petrol brush, you can see various high-tech devices, which are inherent in a set of operational characteristics, including such parameters as increased productivity and a long service life.

A convenient and reliable trimmer is a technical device consisting of individual mechanisms, parts and elements that can wear out, become unusable and damaged during intensive use.

Even with regular technical inspection, maintenance procedures and careful storage, such devices and their individual parts require repair and even replacement, all repair procedures can be performed independently.

Brief content of the article:

The easiest way is to give the petrol cutter for repairs, having allocated a certain amount of funds from the family budget, prompt and high-quality repair with your own hands is no less simple and convenient if you want to understand the design of the petrol cutter and fix all the problems.

The mass and piece production of trimmers is based on the use of generally accepted technology, a typical design scheme consists of certain elements and parts, it is important to know them when carrying out independent repair work:

top part. The basis of the entire structure, where all the important elements are collected, such as a starter, a carburetor and a petrol cutter engine;
middle part. A hollow rod, inside it is a cable that connects the motor and the gearbox, which drives the cutting line. In this part, there are fasteners for distributing the weight of the entire structure and a belt for fixing the trimmer on the belt of a person using the trimmer for its intended purpose;
Bottom part. It houses the gearbox and cutting elements, which are hidden under a practical cover to protect the user. The casing provides an increased level of safety, preventing large fractions of debris, stones and glass from entering a person while working with a petrol cutter.

Knowing exactly the internal structure and the principle of operation of the trimmer, you can independently carry out repair measures for the structure or replace individual components that have become unusable, using the repair instructions.

The most common and common failures of the unit that need to be corrected on their own include the following problems:

engine malfunction, due to which the brushcutter does not start and does not work;
increased vibration of the brushcutter bar, which complicates its intended use;
increased overheating of the gearbox, its accelerated heating during operation;
slow and weak functioning of the cutting line at insufficient speed;
clogging of the starter grille, causing overheating of the engine and its refusal to work;
fast and frequent clogging of the carburetor due to the use of low-quality fuel;
clogging of the air filter due to non-observance of the measures for the care of the device.

All these problems can lead to the fact that the device will lose its working capacity. Before ordering the necessary spare parts for the mowing, a visual inspection and diagnostics of the device should be carried out.

Particular attention should be paid to individual spare parts and units of the device, to check them you will not have to contact a professional master, a set of diagnostic measures will help you to identify the consequence of a loss of performance with your own hands.

If the trimmer motor does not start or stalls immediately after starting, when the gearbox overheats or during the operation of the device, extraneous noises are heard and vibration is clearly felt, it is important to visually inspect and identify a non-working unit.

To optimize the preparatory measures before repairs, you should carry out a simple diagnosis and check in stages:

the presence of fuel in the tank and lubrication in the main units;
serviceability of the spark plug and its performance;
the cleanliness of the fuel and air filter of the brushcutter;
clogging of the outlet channel and breather of the device;
the quality of the fuels and lubricants used.

To determine the functional performance of the petrol-cutter's ignition, it is necessary to determine whether the spark plug is working by testing the appearance of a spark when it comes into contact with the body of the functional device.

The spark plug itself can be replaced with a new one, having previously dried the candle channel, if necessary, the old element is also dried, cleaned with special devices and returned to its place.

In the process of inspecting the carburetor, it is worth paying attention to the possible leakage of the fuel used; in order to identify problems with the carburetor, the following measures must be taken:

purging the fuel hose to eliminate possible blockage of the element;
checking and replacing the gasket between the engine and the carburetor;
determination of tightness and maintenance of constant pressure in the unit.

If necessary, you can personally disassemble and thoroughly clean the unit using gasoline, the jet and channels are cleaned using compressed air.

The gearbox transmits torque from the motor shaft to the cutting tool, its gears during operation must be absolutely clean and always lubricated with special grease.

Carrying out a technical inspection on your own once a season will allow you to get rid of the need to repair the gearbox or replace it, with the purchase of an expensive new unit.

The starter is necessary to bring the trimmer into working condition, its diagnostics consists in checking the tension of the starter cord connected to the teeth of the starter coil, which are often destroyed during an abrupt start.

A non-working starter in a petrol cutter cannot be repaired; it must be replaced with a working unit as part of a mandatory technical inspection or a set of repair measures.

Cutting elements require special attention and care, which must always be cleaned of dirt and cut grass after use. Regular inspection and thorough preparation of the device for operation will help to avoid costly and time-consuming repairs, and always be confident in the performance of the petrol brush.

Carburetor repair of mowers Very often complaints of owners of gasoline trimmers are associated with various kinds of defects in the carburetor. Naturally, it is most ideal in this case to seek help from a specialist.

Very often, complaints from owners of gasoline trimmers are associated with various kinds of carburetor defects.

Naturally, it is most ideal in this case to seek help from specialists in this field, for whom the repair of carburetors of gasoline trimmers is an integral part of the profession.

Do not try to repair the device without the help of others, since repairing the carburetor of the mowers with your own hands can lead to even greater damage and even huge costs for fixing it.

But if you are still familiar with the basic mechanisms of the trimmer carburetor, you can try to figure out the dilemma yourself, so as not to overpay in the service, because from time to time the breakdown can be really frivolous.

This article is just created in order to help you cope with the malfunction.

Further, more often encountered breakdowns and the prerequisites for their occurrence will be sorted out.

First, you should generally look at the carburetor and find out if there is any fuel leakage.

If it turns out that there are no problems with fuel, you need to remove the carburetor from the engine and check the condition of the gasket located next to the carburetor.

If no defects are observed here, you can test to check the carburetor for the degree of density.

To do this, you can purchase a special device, which is part of the tool kits for repairing the carburetor of brushcutters and representing a special pressure gauge that, in fact, inspects the density.

Curious! The benzokos stalls, here!

If you do not want to spend money on its purchase, you can use an ordinary honey tonometer, on which you just need to change the pressure gauge.

When using this device, pay attention to the indication.

If the pressure does not drop and remains similar over time, you can be measured, as this indicates the density of the carburetor.

If the pressure begins to decrease after a certain time, it means that there are still difficulties.

They can be associated with damage to some parts of the carburetor.

In this case, the only way out is to replace the faulty parts with new ones. In addition, clogging of channels or jets can become a prerequisite for malfunctioning of the carburetor.

Even ordinary drops of water can play a negative role here, which can clog the openings of the jets or channels.

If you find a lack of density in the carburetor, wash it outside with gasoline and disassemble.

Remember that in order to repair the carburetor of the brushcutter yourself, channels or nozzles, you cannot use needles or iron wire, as they can change the flow sections.

These are the main faults in the carburetor that you can easily fix without the help of others.

If you did not find any of the listed problems in your own carburetor, it is recommended to contact a special service for help.

Petrolcutters, like all petrol powered tools for the garden, are not difficult to maintain. It is possible and necessary to repair, configure without the help of others. For example, adjusting the carburetor of a petrol cutter with your own hands is a matter of 5 minutes.

The carburetor from the petrol cutter is a unit in the power system. In it, like all carburetors, there is a process of mixing air and fuel (gasoline) for the forthcoming supply to the engine cylinders.

In this process, the main thing is the correct proportion of fuel and air, which is why the carburetor is regulated.

Mesh filter. With this element, most often there are only two difficulties:

In order to find out the cause of the breakdown, the fuel filter cap is unscrewed to remove the strainer. If dirt has simply accumulated on it, then flushing in gasoline or blowing will help.

If there is visible damage to the mesh filter, it is imperative to install a new one. There may also be damage to the fuel supply pipe (during repairs, they practice checking this element).

The carburetor starter almost always does not work due to blockages. Use acetone or the same gasoline for flushing.

Blowing out parts of a carburetor with a blockage with compressed air is an acceptable and comfortable repair practice.

The body of the throttle valves, the places of the bundles of the carburetor parts, the inlet or outlet pipeline - all of these parts are susceptible to depressurization. You can probably check with a simple method - smear the problem area with soapy foam.

Read also: DIY car ECU repair

On trimmers, in addition to electric motors, gasoline internal combustion engines are installed. This mechanism requires special attention to itself, because if it is incorrectly configured, it will either refuse to work, or it will work intermittently and loss of power. Basically, engine tuning is about adjusting the fuel supply, and this is done with the help of the carburetor trimmer.

It is almost impossible to cover all types of carburetors produced by manufacturers of gas trimmers. But, since the design of this module, as well as its principle of operation, is largely similar between different models, a generalized description of the processes occurring in the carburetor can be made. This information will allow the user to understand the principles of operation of the device, to eliminate the malfunctions that have arisen and to operate it correctly.

The carburetor trimmer is based on one-piece aluminum body... Below is a diagram of this block.

At the bottom of it, there is a diffuser, which is also called Venturi nozzle (eighteen). Air is drawn in by the motor through this nozzle.

The smaller this hole, the faster the air flows, and the higher the level of its vacuum in the zone with the smallest diameter.

At the top of the diffuser are fuel channels (11.12). Through these channels, the air flow draws in gasoline. The fuel pump itself, jets and the system used to regulate the supply of the fuel-air mixture can be built-in or installed externally.

Throttle valve (9) adjusts the amount of air sucked into the carburetor. Its amount affects the power that the engine develops. The damper (7) is used for cold starting. It must be closed if you are going to start the unit. After the engine has started, it must be opened, otherwise, the engine will immediately stall.

Impulse channel (1) connects the impulse chamber of the pump to the crankcase of the engine, namely, to its internal volume.The piston in the cylinder, making reciprocating movements, successively changes the pressure in the crankcase (vacuum or pressure increase). The pressure drops force the diaphragm (4) to move. Therefore, the operation of the pump is synchronized with the operation of the engine.

The suction of gasoline from the tank occurs precisely with the participation membranes (4). Gasoline enters the carburetor through the union (2). Further, its path lies through the inlet valve (3), the outlet valve (5), through the mesh filter (6), the fuel channel (10), passes the needle (14) and fills the chamber (16), which has a control diaphragm (18) ...

The valve (14) is connected to the diaphragm (18) by means of a lever (17). The cavity, which is located below the membrane, is connected to atmospheric air through the hole (19).

The device operates as follows.

A vacuum is generated in the diffuser during the suction stroke. This fact causes air leaks. The position of the throttle valve (9) determines the amount of air entering the carburetor chamber, as well as the engine power and the number of revolutions.
At this time, fuel is sucked in from the chamber (16) through the jets (11,12), after which it is mixed with the flowing air. Gasoline, mixing with air, begins to spray. Thus, a air-fuel mixture.
The finished mixture enters the cylinder, where it is compressed by the rising piston and ignited at its highest point from the spark generated by the spark plugs.
Since the volume under the control diaphragm (18) is connected to atmospheric air through the channel (19), the diaphragm goes up, opening the valve (14) by means of the lever (17). After opening the valve (14), a new portion of fuel enters the chamber (16).
After the chamber (16) is full, the diaphragm (18) returns to its original position and the valve (14) closes.

Further, when the motor is running, all the above processes are repeated. A screw (13) is used to adjust the amount of fuel entering the diffuser through the nozzles. The screw (15) is also used to adjust the idle speed. When the regulators are twisted, the fuel mixture is enriched, and when the regulators are twisted, the mixture becomes lean. Also, in some models of carburetors, you can adjust the idle speed of the engine. quantity regulator... It is usually located outside and, when twisted, abuts against a lever attached to the throttle shaft.

Thus, using 3 adjusting screws, you can achieve maximum engine performance, as well as adjust its smooth operation at any ambient temperature, and even in mountainous areas.

Failure of the trimmer carburetor occurs due to the use of poor quality gasoline, a damaged air filter and the accumulation of dirt in the chamber of this unit. Most often, it is quite possible to repair the carburetor with your own hands. Listed below are typical brushcutter carburetor malfunctions.

A common malfunction that "haunts" the fuel pump is deformation of the pump diaphragm... For this reason, it does not fit properly and the pumping passages are not sealed.

The reasons for membrane deformation can be the following:

long work of the trimmer;
use of unsuitable fuel;
ingress of gases into the impulse channel.

As a result, diaphragm damage reduces pump performance and, as a result:

depletion of the combustible mixture occurs;
it is difficult to start the engine;
there are interruptions in the operation of the motor;
the piston is damaged.

Also, the above-described consequences for the engine can cause clogging of the pump cavity with impulse side... In this case, dirt enters the membrane through the impulse channel.

To clear the blockage, you will have to disassemble the carburetor and clean the membrane.

The strainer can become clogged if contaminated fuel enters through a defective fuel hose or pickup head.In the photo below you can see what a clean filter looks like and a dirty one (parts are separated by a line).

Troubleshooting will require a thorough cleaning and rinsing of the strainer. Also recommended blow with compressed air all holes in the carburetor trimmer housing.

This failure occurs when the contact surface of the lever wears out.

The abrasion of the contact surface occurs due to the presence in gasoline abrasive particles or due to strong vibration of the motor during operation. This defect in the control lever causes problems with the intake, as well as improper idling of the engine.

The inlet needle breaks down, as a rule, due to the presence of abrasive particles in the fuel fluid.

the tightness of the inlet needle seat is disrupted;
there is a leakage of a combustible mixture;
there are malfunctions in the engine operation associated with re-enrichment of the fuel mixture.

Also, the inlet needle may just jam.

A jammed inlet needle can cause the presence of dirt in the fuel, or a long idle device without work.

If dirt accumulates in the control cavity, the inlet needle cannot close the hole tightly and a lot of fuel pours into the chamber.

It causes re-enrichment of fueland the engine starts to malfunction. It is necessary to disassemble the carburetor and clean the cavity of the control membrane.

The membrane can undergo deformation during prolonged operation of the unit and when using aggressive fuels.

Failure of normal adjustment due to a defect leads to:

damage to the piston;
difficulties when starting up;
depletion of fuel;
improper engine operation.

This problem can occur if the adjusting arm is not properly installed or if it is bent before installing. As a result, the contact surface is in the wrong position, which disrupts the additional fuel supply.

The throttle and choke valves are mainly subject to wear due to the presence of abrasive particles in the air. Defective flaps look like they have been sandblasted.

As a result of valve wear, engine performance decreases, malfunctions appear in its operation, piston rings, piston and cylinder coating wear out.

The air and throttle shaft can wear out for the following reasons:

insufficient and improper maintenance of the air filter;
the air filter is damaged;
the air filter is not suitable for this unit.

Due to hit poor quality purified air, the shaft will wear out and may break. Broken shaft parts can enter the combustion chamber or crankcase and cause serious damage to the entire piston system.

To eliminate problems with air purification, it is necessary to replace the defective filter or flush the existing (serviceable) one. The filter must be washed in soapy water and dried.

Carburetor adjustment is necessary in the following cases:

the new engine was run-in (4-5 liters of fuel mixture were used);
the composition of the fuel has changed (brand of oil and gasoline);
the weather has changed (it became hot, cold);
the rarefaction of air has changed (applies to mountainous regions);
after long-term storage;
increased load on the engine (after changing tools, etc.);
due to vibration, the adjustment screws spontaneously unscrewed;
fuel consumption has increased, the carburetor overflows fuel;
carbon deposits quickly appear on the spark plug electrodes (while the fuel mixture is prepared correctly);
the engine starts and immediately stalls or gains momentum poorly;
gasoline does not enter the cylinder;
a large amount of exhaust gases.

Before you start adjusting the carburetor trimmer, you must do the following:

flush the engine;
replace or clean the spark plug;
change to a new one or clean the air filter (it is recommended to wash it in warm, soapy water, wring it out and let it dry well).

It is also necessary set cord a suitable diameter in the trimmer coil or install knives - this is done so that during the tuning process the engine has at least some kind of load. After installing the cutting tool and starting the gasoline engine, let it warm up for 10 minutes.

If at idle motor, you notice that the cutting tool is rotating, so it is necessary to reduce the engine speed. This is done using the lower idle speed control, often marked with the letter “T”. The illustration below shows the placement of the adjusters on a Husqvarna trimmer.

But, for example, on a Stihl trimmer, this screw may be marked “LA”.

So, turn the idle speed control to the left until the trimmer head comes to a complete stop.

To adjust the carburetor, 3 regulators (screws) are used.

Right adjuster L adjusts the level of enrichment of the combustible mixture at low speeds. It needs to be regulated first. Achieve maximum idle speed. This is done with the L knob by turning it left and right. After finding the point of maximum speed, return the regulator half a turn to the left (counter-clockwise).
Lower T adjuster (LA) used to adjust idle speed. Turning it to the left, the engine speed will begin to decrease, and turning the regulator to the right, the engine speed will increase.
Left Knob H is responsible for enriching the combustible mixture at high speeds. The enrichment setting completes the carburetor setting. Also, using this regulator, you can adjust the maximum speed, fuel consumption and engine power.

Important! If the engine is allowed to run at full speed for more than 10 seconds, it may fail.

To eliminate this nuisance, adjustment will be required. With the engine running, give full throttle, then turn the regulator “H” to the right until the speed starts to decrease. After that, the regulator “H” must be slowly scrolled to the left until you hear the uneven operation of the engine. Then you should turn the knob “H” to the right until the moment when smooth operation of the motor is heard.

After carrying out the above steps, the carburetor setting can be considered complete. After correct adjustment, the engine should confidently pick up speed, a little quarter at maximum speed, and when idling, the cutting tool should not turn. This manual is suitable for adjusting carburettors on Huter, Patriot and other brushcutters.

There are also carburettors without screw, responsible for the enrichment of the combustible mixture at low speeds. That is, they have only 2 adjusting screws: an idle speed regulator and a fuel mixture quality regulator at high speeds. How to tune this type of carburetor can be found in this video.

Video (click to play).