Idle Adjustment On The Trimmer Video

17th June 2020

How to adjust carburetor on trimmer

The increased fuel consumption and the rapid formation of soot on the lawn mowing candles when using a correctly prepared fuel mixture indicate the need for carburetor adjustment. This describes how to set trimmers with carburetors that have one screw for adjusting the fuel supply.

Carb adjustment

Flush the air filter before adjusting the carburetor. It is recommended to rinse it after every 10 hours of operation. After that, you can begin to adjust. The example photograph shows the carburetor of the gasoline trimmer PRORAB-8406. The numbers indicate the adjusting screws that we will use.

Prorab-8406 gas trimmer carburetor adjusting screws

Purpose of adjusting screws:

Fuel mixture adjusting screw.
Idle adjustment screw.
The screw limits the maximum speed.

Start the lawn mower and wait until it warms up.

Fuel adjustment

Start slowly tightening the fuel mixture adjusting screw until the engine stalls or stalls unless you catch the moment. Then unscrew the screw a quarter of a turn if the engine is not dead, or half a turn if it is dead. Start the stalled engine. Check, by opening the throttle, how the engine accelerates. Continue to loosen screw # 1 a quarter of a turn until the engine starts to confidently gain high revs when progazovka. This will be the moment of the most economical stable engine operation. At the PRORAB-8406 gas trimmer, the adjusting screws are turned clockwise, unscrewed. Against, for some other brands the lawn mowing may be vice versa.

Idle adjustment

We proceed to adjust the low speed. Screw number 2 restricts the return movement of the throttle lever. By wrapping it, we increase idle speed, unscrewing. Reduce it. Adjust so that the engine runs confidently at low speeds and even slightly faster (for a better start), but so that the reel with fishing line or knife does not rotate, and before starting to rotate, there is a sufficient margin of speed. If the engine starts poorly, still increase idle speed.

Maximum speed limit

After adjusting the flow of the fuel mixture and low revs, check how the lawn mowing engine will operate at maximum speed. If necessary, limit the maximum speed to the required level using the No. 3 hollow screw. Loosen the locking nut and screw in to decrease the maximum speed or unscrew to increase. After adjustment, tighten the nut. Setting the maximum speed is necessary to protect the trimmer motor from overheating and the ability to use the release key lock to reduce fatigue of the right hand.

In the future, it may be necessary to adjust the trimmer carburetor. For example, if the engine, when operating at full load, starts to pick up revs poorly, loosen screw No. 1 another quarter of a turn. If it is difficult to start, increase the idle speed. Weather conditions and the quality of the fuel mixture can affect the operation of lawn mowers. The vibration can also make the adjusting screws turn themselves.

The spring may interfere

My first attempt to adjust the carburetor of the lawn mowers did not work, as the spring of the fuel mixture adjustment screw prevented it. The factory spring turned out to be too thick in a compressed state and did not give the opportunity to reduce the fuel supply to the required level. I had to pick up another spring and continue adjusting after replacing it.

Spring mixture adjustment screw

In the photo above, the factory spring, below the adjustment screw with a selected spring. I am writing about this, because I’m not sure that this is an isolated case, and someone else may encounter the same situation.

From personal experience

Lawn mowing or trimmer

A trimmer is a broader concept than a lawn mow (lawn mow), since it can also be electric. A gas trimmer and a lawn mower are one and the same.

Some authors claim that the trimmer is a weaker tool, in contrast to the more powerful lawn mowers, which can be used to mow shrubs. Personally, I have a tool with a maximum power of 1.7 kW and capable of mowing a small shrub up to 10 mm thick, as stated in the instructions. The user manual is called “Petrol trimmer. “.

Fuel mix ratio

I read somewhere that if in the instruction manual for lawn mowers and on the canister with oil different proportions of the preparation of the fuel mixture are indicated, the proportion indicated in the manual should be used.

It did so for a long time. Excess oil flowed from the engine to the gas tank and soot was constantly forming on the candle, since the manual indicated the proportion for the engine being run in 1:25, and on the canister. 1:50. After the transition to a proportion of 1:50, the appearance of oil drips stopped. The candle continued to burn, but with less intensity (the carburetor was not yet adjusted).

Until now, some users of gasoline tools determine the proportion of the fuel mixture “by eye”. If during the preparation of the mixture the amount of oil is underestimated, after some time an extraneous sound may appear immediately after the engine starts, gradually disappearing during warming up, and the engine stops with a sharp jerk. Continued operation of the trimmer in this mode will lead to its failure.

Candle cleaning

In the worst days of working with a trimmer with an unregulated carburetor, the engine stopped starting after using each fuel tank. And only after cleaning the candles from soot could we continue to work.

To clean the electrodes, fine sandpaper was used, and to clean the space between the insulator and the body, a thin clerical clip with a bent end was used. First, the electrodes were wiped off with a lot of dirt with a rag, then they were cleaned with sandpaper. After that, the candle was lowered into diesel fuel and the moistened soot was scraped off with a paper clip from the surfaces of the insulator, the inside of the housing and between them. Further, the candle was lowered several times in diesel fuel, which was then shaken off from it along with impurities. Sometimes the cleaning procedure with a paper clip and washing are repeated. After that, the candle was wiped dry and was ready for further use.

Incredibly, one tank of the fuel mixture with an unregulated carburetor can be consumed in less than 10 minutes. It was tested in practice when the trimmer was started and operated at high speeds with maximum fuel supply (the adjusting screw was unscrewed much more than normal).

Carburetor trimmer trimmer trimmer: 57 comments

Explainably, concisely and clearly. Thank!

Thanks, I would also find a Chinese screwdriver and everything is clear to the gas. I give it it’s not gaining momentum. The carburetor is new.

Hello Eugene, can you tell me for what reasons there was a vibration on the gas trimmer when mowing, thank you in advance

Hello Oleg. If your trimmer has been in use for more than a year, then it may need to lubricate the shaft shaft. Pay attention to the condition of the bearings.

He greased the shaft, began to calm a little, and which bearings should I pay attention to?

Oleg, since you did not notice the bearing, as in the in which the coupling is pressed in, then you do not have it. My trimmer does not have one either (the shaft is freely removed from the top of the rod in the direction from the engine, as in the, but only after removing the retaining ring from the shaft on the engine side, and the coupling is an extension of the shaft). Four more bearings in the lower gear.

See if there is any side play on the gear shaft, to which the drum with fishing line or knife is attached, if there are any extraneous sounds during rotation. If you use a knife, it can be unbalanced from the uneven distribution of damage on the blades or their deformation, which leads to increased vibration.

Oleg, if you can find and eliminate the cause of increased vibration, write what it was.

I can not help but give a link to the Dismantling and repair of the lower gear of the lawn mowing, trimmer, where the problem bearing is removed using a loaf of crumb. This is the know-how!

There, in the comments, there is advice when disassembling the lower gearbox, first remove the drive shaft, the gear of which interferes with the output of the output shaft bearing. Then, if the seat on the driven shaft is not broken, the problem bearing is removed along with the shaft.

Well, if I find something, unsubscribe

Sorry, Eugene for importunity, another question, the upper gearbox, where does it need to be lubricated?

Oleg, I’ve never taken it apart and I think it’s not worth it until the bearing breaks or the clutch breaks. There, in front of the cover, there is only a bearing and a coupling (sleeve) with splines, into which the shaft is inserted and which is lubricated with it, it is accessible without dismantling. Next comes the clutch.

Thanks, everything is clear

How to adjust the carburetor if not 6th what kind of adjustment on it?

Alexander, specify a question.

Hello, I have a Patriot 5555 trimer, the problem is that when you type gas, you can hear it sounding like something, tell me what it is?

Hello, Nikolai. Have you tried to change a candle?

I tried everything as well.

Nikolay, I have all the problems with the difficult start of the trimmer and engine interruptions that were connected with the ignition system, or rather, with the breakdown of the spark plug insulator and the breakage of the high-voltage wire in the cap. They also write that the ignition coil may fail.

To make sure that your problem is related to ignition or not, check for a spark on a cold engine and after a little warm-up (the candle should be hot, but unscrewed freely). If in both cases the spark is interrupted, then the cause is in the fuel system.

Hello Eugene, I found the reason, the vibration during mowing was due to a broken coil, there was an uneven ejection of fishing line, but there was still a problem when starting up at idle, the trimmer began to shake a lot, what could be the reason?

Good afternoon, Oleg. Check all engine mounts, including the rod mount to the clutch housing (upper gearbox).

It’s clear, and why the boom mount is why, it is shaking at idle, the clutch does not work at this moment

Lawn mowers, like all gasoline powered tools for the garden, are not difficult to maintain. It is possible and necessary to repair, configure yourself. For example, adjusting the carburetor of the lawn mowers with your own hands is a matter of five minutes.

Lawn mowing carburetor is a unit in the power system. In it, like any carburetors, there is a process of mixing air and fuel (gasoline) for further supply to the engine cylinders.

In this process, the main thing is the correct proportion of fuel and air, for which they regulate the carburetor.

The main problems and malfunctions of the carburetor.

Strainer There are only two problems with this element:

Clogging.
Breakage

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

With visible damage to the strainer, it is imperative to install a new one. There may also be damage on the fuel supply pipe (during repair, check this element).

The carburetor starter in most cases does not function due to blockages. Use acetone or the same gasoline for flushing.

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

The throttle body, the bundles of carburetor parts, the intake or exhaust pipe. All of these parts are subject to depressurization. You can probably check it in a primitive way. Smear the problem area with soap suds.

The device of the carburetor lawn mowers

The basis of the carburetor of the lawn mowers is an aluminum case. It has a diffuser (hole with internal contours). Air is blown through this hole. The oxygen (air) flow rate depends on the cross-section (passage opening) of the diffuser.

The diffuser is equipped with fuel channels. Of these, fuel is drawn in using an air stream.

Outside the carburetor is installed:

Fuel pump;
Jet system;
Fuel / air mixture control system;

The principle of the carburetor lawn mowers

The throttle valve determines the amount of air for supply, and engine power directly depends on this.

Fuel is sucked into the carburetor system by a pump (its membrane). Then it passes through the fitting in the carburetor. Further, the fluid moves through the inlet and outlet valves of the pump. Filtered by mesh. The needle valve moves into the membrane chamber.

Phased operation of the device:

Air supply to the tube with an air baffle (damper). The partition controls the intensity of the air flow.
The fuel supply system must be narrowed by a diffuser to increase the flow rate.
Gasoline through the float chamber and nozzle tube with narrowing. A camera with a float adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with narrowing is already low. Due to the pressure drop, fuel enters through the nozzle.
The acceleration of the air flow contributes to the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the necessary proportion or density is formed.
The air-fuel mixture enters the engine cylinder through the fuel pipe.

The level of air density in the system depends on the area of the open air damper. The wider the flap is open, the greater the fuel consumption and power.

Simply put, adjusting the carburetor on the lawn mower is creating the optimal fuel mixture due to the correct air supply.

How to adjust a carburetor on a lawn mower

Before adjustment, carefully clean the filters according to the maintenance in the instructions.

Further tuning of the carburetor of the lawn mowings with your own hands is done by adjusting screws. There are three of them:

Right (L). Fuel mixture adjustment for low revs.

Need to find the maximum idle speed. To do this, slowly unscrew the screw (L) to the right and left.

To adjust, turn the screw a quarter turn necessarily counterclockwise.

Lower (T). Is responsible for adjusting the engine at idle.

Clockwise. Increase;
Counterclockwise. Decrease.

For proper adjustment of idling, it is typical:

Steady work of the cold engine;
Not overestimated speed of the hot engine;
A large headroom for the trimmer head;
Stable operation of the engine when changing position (sharp rise or lowering of the knife).

Left (N). Adjustment of the mixture at high speeds. (The screw is configured last).

From the left screw (N) depends on the overall adjustment of the maximum speed, engine power, temperature and gas mileage.

Setting the carburetor lawn mowers with the last screw is as follows:

Open the throttle to full, while giving out full throttle. Turn the screw clockwise until the speed drops (in this case, they are oriented by ear).
Turn the screw as slowly as possible counterclockwise until the engine runs unevenly.
Then turn back quite a bit, barely hearing stable, smooth operation.
For a more visual application of skills, it is more convenient to consider the work of an experienced user:

Interestingly, from the point of view of the author of the, the setting (its correctness) is determined by the color of the candle, and not just by the speed and stability of the engine.

The correct setting of the carburetor with your own hands in this case is the combustion of the fuel mixture without residue, the color of the candle should be light brown.

Carburetor adjustment of lawn mowers in practice.

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

How is the gas trimmer carburetor arranged and working

All varieties of carburetors produced by manufacturers of gas trimmers are almost impossible to cover. 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, eliminate the problems that have arisen and operate it correctly.

The basis of the trimmer carburetor is a one-piece aluminum housing. Below is a diagram of this unit.

At the bottom of it is a diffuser, which is also called a Venturi nozzle (18). Air is sucked in by the motor through this nozzle.

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

In the upper part of the diffuser there are fuel channels (11,12). Through these channels, the flow of air draws in gasoline. The fuel pump itself, the jets, and the system used to regulate the flow of the fuel-air mixture can be built-in or installed externally.

The throttle (9) controls the amount of air drawn into the carburetor. Its amount affects the power that the engine develops. The damper (7) is used for cold start. It must be closed if you intend to start the unit. After the engine starts, it needs to be opened, otherwise, the motor will immediately stall.

The pulse channel (1) connects the pulse chamber of the pump to the crankcase, namely, with its internal volume. The piston located in the cylinder, making a reciprocating motion, successively changes the pressure in the crankcase (vacuum or pressure increase). Pressure drops make the membrane move (4). Therefore, the operation of the pump is synchronized with the operation of the engine.

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

The device operates as follows.

A vacuum is created in the diffuser during the suction stroke. This fact causes air leaks. The amount of air entering the carburetor chamber, as well as the engine power and the number of revolutions depends on the position of the throttle valve (9).
At this time, fuel from the chamber (16) is sucked through the jets (11,12), after which it is mixed with the flowing air. Gasoline, mixed with air, begins to spray. Thus, an air-fuel mixture is created.
The finished mixture enters the cylinder, where it is compressed by a rising piston and ignites at its correct point from the spark generated by the spark plugs.
Since the volume under the control membrane (18) is connected to atmospheric air through the channel (19), the membrane 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 membrane (18) returns to its original position, and the valve (14) closes.

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

Thus, using 3 adjusting screws, it is possible to achieve maximum engine performance, as well as to configure its uninterrupted operation at any ambient temperature, and even in mountainous areas.

Common carburetor malfunctions

Damage to 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 a carburetor with your own hands. Typical malfunctions of the carburetor lawn mowers are listed below.

Fuel pump problems

A common malfunction that “chases” the fuel pump is deformation of the pump diaphragm. For this reason, it does not fit properly and the pump channels are not sealed.

The causes of membrane deformation can be as follows:

Long operation of the trimmer;
Use of unsuitable fuel;
Gas entering the pulse channel.

As a result, damage to the membrane reduces the performance of the pump, and as a result:

There is a depletion of the combustible mixture;
Difficulty starting the engine;
There are interruptions in the motor;
The piston is damaged.

Also, the aforementioned consequences for the engine can cause clogging of the pump cavity on the pulse side. In this case, dirt enters the membrane through the pulse channel.

To eliminate clogging, you will have to disassemble the carburetor and clean the membrane.

Strainer clogging

The strainer may become contaminated when contaminated fuel enters through a fuel hose or defective suction head. In the photo below you can see what a clean filter looks like and dirty (the parts are separated by a dash).

A thorough cleaning and rinsing of the strainer will be required to resolve the malfunction. It is also recommended that all openings in the trimmer carburetor body be blown with compressed air.

Adjustment lever defective

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

The contact surface is erased due to the presence of abrasive particles in gasoline or due to strong vibration of the motor during operation. This defect of the adjusting lever causes problems with the inlet, as well as improper engine idling.

Inlet needle wear

The intake needle fails, usually due to the presence of abrasive particles in the fuel fluid.

The tightness of the seat of the inlet needle is violated;
Leakage of the combustible mixture appears;
There are malfunctions in the engine associated with the re-enrichment of the fuel mixture.

Also, the inlet needle can simply jam.

Jamming the inlet needle can cause dirt in the fuel, or a long idle time without working.

Clogged control cavity

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

This causes re-enrichment of the fuel, and the engine starts to work incorrectly. It is necessary to disassemble the carburetor and clean the cavity of the adjusting membrane.

Adjustment membrane deformation

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

The impossibility of normal adjustment due to a defect leads to:

Piston damage;
Difficulty in starting up;
Fuel depletion;
Engine malfunction.

Inlet Adjustment Lever Problem

This problem may occur if the adjusting lever is not installed correctly or bent before installation. As a result, the contact surface takes the wrong position, which disrupts the additional fuel supply.

Damper wear

Throttle and air dampers mostly wear out due to the presence of abrasive particles in the air. Defective flaps look like they were sandblasted.

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

Throttle and air damper shaft wear

The air and throttle shaft may 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 the ingress of poorly cleaned air, the shaft wears out and can break. Broken parts of the shaft can enter the combustion chamber or engine 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 rinse the existing one (serviceable). The filter must be washed in soapy water and dried.

When to adjust

Carburetor adjustment is necessary in the following cases:

The new engine was tested (4-5 liters of fuel mixture were used);
Fuel composition has changed (brand of oil and gasoline);
The weather has changed (it has become hot, cold);
Rarefied air (applies to mountainous areas);
After prolonged storage;
Increased engine load (after changing tools, etc.);
Due to vibration, the adjustment screws spontaneously unscrew;
Increased fuel consumption, carburetor overfills fuel;
Carbon deposits quickly appear on the spark plug electrodes (while the fuel mixture is prepared correctly);
The engine starts and immediately stalls or picks up poorly;
No gas enters the cylinder;
A large amount of exhaust gas.

How to adjust

Before setting up the trimmer carburetor, 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, squeeze it out and let it dry well).

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

If at idle of the engine you notice that the cutting tool rotates, then it is necessary to reduce the engine speed. This is done using the lower idle control, often marked with the letter “T”. The figure below shows the placement of the knobs on the Husqvarna trimmer.

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

So, turn the idle speed control to the left, until the trimmer head stops completely.

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

The right knob L adjusts the level of enrichment of the combustible mixture at low speeds. It needs to be regulated first. Get maximum idle speed. This is done using the L knob, turning it left and right. After finding the point of maximum revolutions, return the regulator half a turn to the left (counterclockwise).
The lower T (LA) knob is used to adjust the idle speed. By turning it to the left, the engine speed will begin to decrease, and when you turn the regulator to the right, the speed will increase.
The left regulator H is responsible for the enrichment of the combustible mixture at high speeds. The enrichment setting completes the carburetor adjustment. Also, using this controller, you can adjust the maximum speed, fuel consumption and engine power.

Important! If you allow the engine to work at full speed for more than 10 seconds, then it can fail.

To eliminate this trouble, adjustment will be required. With the engine running, give full throttle, then turn the “H” knob to the right until the speed decreases. After that, the “H” knob must be slowly turned to the left until you hear the engine running unevenly. Then turn the “H” knob to the right until the engine runs smoothly.

After carrying out the above steps, the carburetor setting can be considered completed. After proper adjustment, the engine should confidently gain speed, a little four at maximum speed, and when idling, the cutting tool should not turn. This manual is suitable for adjusting carburetors on lawn mowers Huter, Patriot and others.

There are also carburetors without a screw, which is responsible for the enrichment of the combustible mixture at low speeds. That is, they have only 2 adjusting screws: the idle speed regulator and the fuel mixture quality regulator at high speeds. You can learn how to tune this type of carburetor from this.

Maria Sukhorukikh

The standard design of any gas trimmer must include a fuel system, the basis of which is the action of a standard carburetor. Its structure and initial principle of operation are almost the same for all lawn mowers, regardless of their design features and purpose.

The lawn mowers carburetor consists of an all-metal aluminum housing that protects the internal components of the assembly from moisture, small debris and dust. A built-in diffuser is provided in the lower part of the body, the second name of which is “Venturi nozzle”. The main function of this standard part is to supply air in the amount required by the fuel assembly to enrich the fuel. The diffuser operates according to a simple principle: the smaller its diameter becomes, the more intensively the air is absorbed. This is due to the fact that in the zone of the smallest diameter the level of air discharge becomes maximum.

The upper part of the built-in factory diffuser is pre-equipped with fuel pipes, through which, under the influence of air, the fuel mixture is drawn in. Other carburetor parts: regular adjusting screws and a fuel pump, can be located both inside and outside the carburetor.

The carburetor of the lawn mowers includes a throttle, the main task of which is to regulate the amount of intake air. The greater the amount of air, the higher the rated power of the trimmer power unit. Another function of the damper is to facilitate the cold start of the engine. If the lawn mowing is started for the first time after a long period of inactivity, the shutter must be closed. Immediately after starting the motor, the part must be opened, otherwise the engine will die out.

The carburetor for the trimmer is equipped with a pulse channel that connects the internal cavity of the ICE crankcase with the pulse chamber of the pump. The piston located in the cylinder of the motor creates a reciprocating motion, which leads to gradual changes in pressure inside the crankcase. At the same time, the membrane is driven. Thus, the action of the pump is fully synchronized with the operation of the power unit.

The membrane of a regular carburetor takes an active part in fuel suction. It enters the fuel assembly through the fitting. After that, the fuel passes through the built-in intake and exhaust valves, then through the strainer and the fuel pipe. Then the fuel flows next to the needle and gradually fills the chamber equipped with a control membrane.

The regular valve of the trimmer carburetor is connected to the membrane using a lever. Below the built-in membrane is a cavity into which air is drawn in through a special opening.

The carburetor for lawn mowers works on this principle in stages. This ensures uninterrupted operation of the fuel unit and uninterrupted supply of fuel to the cylinder of a standard power unit.

When is the carburetor adjustment of a household trimmer required?

Adjust the built-in trimmer carburetor when:

Running-in of a new engine, during which from 4 to 5 liters of fuel mixture were used;
Sudden changes in weather;
Changes in rarefaction of air. For example, when the lawn mowing is often used in mountainous areas;
Long simple trimmer;
Intensive growth of loads on the power unit of lawn mowers;
Arbitrary unscrewing of the carburetor’s built-in adjusting screws. This becomes the cause of increased vibration of the internal combustion engine;
Changing the quality of the components of the fuel mixture;
Fuel transfusion with a carburetor, resulting in an increase in fuel consumption;
Regular appearance of a thick layer of tarry deposits and soot on the surface of the electrodes of a regular trimmer spark plug;
Engine start and its arbitrary shutdown or a slow set of revolutions;
The lack of fuel in the cylinder of the power unit;
Increase in exhaust emissions.

The lack of timely adjustment of the carburetor threatens serious damage to the trimmer, up to the complete failure of its factory engine.

DIY carburetor adjustment

Periodic adjustment of the trimmer carburetor should be performed on a serviced and fully functional power unit. Before starting the procedure, the operator must thoroughly rinse the engine parts and inspect its CPG for any burrs or other defects. In addition, you will need to clean or replace the spark plug, as well as rinse the filter elements in the construction of the lawn mowers.

During carburetor adjustment, the lawn mowing engine must run under a certain load. It is best to install a cord of the appropriate diameter or cutting knives on the trimmer.

After mounting the cutting organs, the operator should start the internal combustion engine trimmer and leave it to work for about 10 minutes. If during operation of the power unit at idle it was noticed that the cord or knife rotate, then you need to reduce the speed created by the motor. To do this, turn the lower control, often denoted by the letter “T”, to the left, until the installed cutting unit stops completely.

A further configuration of the fuel assembly is as follows:

The “L” regulator, located on the right, is responsible for enriching the fuel mixture with air while the engine is operating at low revs. The position of this screw must be set first. To do this, the operator will need to achieve maximum engine speed when idling. For this you need to turn the screw “L” in turn to the right or left side. Once the maximum speed is reached, the screw will need to be rotated 1/2 turn to the left;
Screw “T” or “LA” is required to adjust the idle speed. During its rotation to the left, the revolutions of the power unit will decrease, and when turning to the right. Accordingly, increase;
The “H” regulator, provided on the left, is responsible for enriching the fuel mixture with air during the operation of the engine trimmer at high speeds. This screw is also needed to adjust motor power and fuel consumption. Its position is adjusted by turning the screw to the right or left side until the maximum permissible engine speed is reached. After that, screw “H” will need to be turned 1/2 turn to the left.

The sequential implementation of these actions will allow you to correctly configure the trimmer fuel assembly, without the risk of exceeding the permissible load on its main operating mechanisms.

The device and carburetor adjustment on lawn mowers and trimmers

Lawn mowing or trimmer with internal combustion engine require not only constant refueling of the fuel mixture of gasoline with oil, but also periodic adjustment of the supply of this fuel. The carburetor is responsible for supplying fuel to the lawn mowing cylinder, the efficiency and productivity of the tool depend on the proper operation of which. If a malfunctioning (abnormal) engine operation is detected during operation, the first thing to do is adjust the carburetor of the lawn mowing machine. Before setting up the carburetor of the gas trimmer, we will first deal with its design.

Design of a petrol-trimmer carburetor and its purpose

Lawn mowers are equipped with push-pull type internal combustion engines. To feed the air-fuel mixture into the engine cylinder, a carburetor is used. In the design of gasoline units. This is a key element without which the operation of the internal combustion engine is impossible. Over, this carburetor differs from the automobile device not only in size, but also in the principle of operation. In particular, this difference lies in the presence of a membrane, which plays the role of a gasoline pump. It is due to the presence of the membrane that the devices under consideration in the design of two-stroke internal combustion engines are called membrane.

Structurally, the entire mechanism is a small-sized part, inside of which there are channels, valves and membranes. The carburetor body is made of aluminum, and the internal device is shown in the photo below.

Before you adjust the carburetor for lawn mowing with your own hands, you need to deal with all the constituent elements of the device in question. The lawn mowing and trimmer carburetor consists of the following parts:

Diffuser or venturi nozzle. Air is sucked into the system through this nozzle
Air damper. Opens and closes the filtered air supply
Fuel channel maximum speed
Fuel channels (jets) of idling XX and medium revolutions
Throttle. The amount of opening is adjusted by pressing the gas
Impulse channel fitting. Connects to the internal channel of the crankcase
Inlet fuel channel (fitting) (2). Provides fuel from the gas tank
Membrane (4). Is responsible for the absorption of fuel from the gas tank
Tank Suction Valve (3)
The valve for supplying fuel to the carburetor channel (5)
Filter element (6) or fuel fine filter
Fuel channel (10)
Needle valve needle (14). Responsible for the fuel supply to the chamber of the control membrane
The chamber is the fuel mixture that is fed through the nozzles and the throttle to the cylinder
Control diaphragm (18). Provides manual primer fuel primer
Lever connected to the membrane (17)
Idle adjustment screw (15)
Screw for adjusting the amount of fuel supplied to the diffuser (13)

Having an idea of how the carburetor is arranged inside, you have to figure out the principle of its operation. A detailed description of how a carburetor works on a two-stroke internal combustion engine using an example of a chainsaw is described in this material.

How does the carburetor lawn mowers or the principle of operation

The carburetor adjustment of the Chinese lawn mowers is completely identical to the adjustment of the lawn mowers of European, Russian and manufacturers. To cope with the task of adjusting the carburetor on lawn mowers and gas trimmers, you need to understand the principle of their functioning. How a carburetor works on a lawn mow, step by step and accessible is described below.

The operation of the carburetor of the lawn mowing begins with the supply of fuel through the channel, as shown in the diagram
The fuel is sucked into the carburetor using a pulse channel connected to the crankcase. Due to the rarefaction of air, the flexible membrane is numbered 4 in the diagram above
Through valves 3 and 5, fuel is supplied. Valve 3 is the inlet, due to which fuel is fed into the submembrane space, and valve 5 is the exhaust
Further, the fuel moves along the channel and, passing the fine filter, reaches the needle valve 14
The needle valve is connected via a lever to the control diaphragm 18
The needle valve is actuated by acting on the membrane. When it is necessary to pump up fuel in order to start the engine, it is necessary to act on the soft cover of the hand pump. When exposed, the needle opens and the chamber fills with fuel mixture
When the engine starts (on a cold one), the opening of the needle occurs due to rarefaction with the air damper closed. This rarefaction acts through the idle and high speed jets on the membrane 18
The membrane acts through the lever on the needle valve, whereby the chamber is filled
After starting the engine, the air damper opens, as a result of which the engine runs on a lean mixture, as the fuel mixes with air
The fuel mixture when the chamber is full is supplied (sucked) through the idle and medium speed jets (when the engine is started)
The throttle valve is shifted from its original position by 10-15 degrees
When the work is carried out under load, the fuel begins to enter the chamber through the high-speed jet, and at the same time, the throttle valve is rotated by an angle of up to 90 degrees (depending on the force of pressing the gas). In all operating modes, an air damper must be opened, through which the fuel is mixed with air, and thereby the mixture ignites in the cylinder

Below is a diagram of the principle of operation of the carburetor lawn mowers. Based on the scheme, you can not only understand the principle of operation, but also identify breakdowns and other malfunctions of the mechanism.

When operating the tool, one more nozzle must be considered. This nozzle is located between the idle and full power channels. It is necessary in order to exclude severe depletion of the mixture, which occurs in the case of engine operation under partial load. In such a situation, the occurrence of a badass pair. Through an additional channel (jet), fuel is sucked into the chamber, whereby the fuel-air mixture is enriched. The following diagram shows an additional nozzle, which is indicated by the number 1.

Having an idea of the design of the membrane carburetor of the lawn mowers and the principle of operation, it will not be difficult to do it yourself. To adjust the carburetor of the lawn mowers, adjusting screws are used. The diagram above shows two screws for adjustment, however, most modern models of gasoline trimmers are equipped with three screws. The presence of three tuning screws allows for more accurate adjustment, while achieving stable and uninterrupted operation of the internal combustion engine.

It is interesting! What is the difference between trimmer and lawn mowing? Many believe that the trimmer is a low-power electric lawn mower. However, the trimmer is a generic name for lawn mowers, lawn mowers and electric mowers, as they are intended for general purposes.

How to find out that the lawn mowing carburetor needs adjustment

Many craftsmen use lawn mowers for a long time, and at the same time do not think about the need to adjust the carburetor of the tool. When is it necessary to adjust the carburetor on a lawn mow or lawn mow? If you ask yourself this question, then surely there are changes in the operation of the motor not for the better. In order not to guess, and not to miss the moment of the need to adjust the carburetor, you should adhere to the following recommendations about the need for adjustment measures:

After engine break-in. Typically, the run-in lasts for 4-5 liters of fuel
When a fuel mixture of a different composition is poured into the tank, that is, the type of oil (even its color) and the brand of gasoline change
With changing weather conditions, however, this is more true for chainsaws, gas generators and motor pumps, which are operated not only in summer but also in winter
If the lawn mower has not been used for a long time. The reason for the need for adjustment may be a winter break
When fuel consumption rises
If black soot is detected on the candle electrodes
In the absence of gasoline in the cylinder or poor engine start
If a large amount of exhaust gas is detected
Unstable operation of the engine, as well as its difficult start and a “sluggish” set of revolutions

As you can see, there are enough reasons for adjusting the carburetor. Typically, craftsmen who work with the tool for a long time, by ear, detect changes in the motor, which promises the need for an adjustment process. Even if you are not sure about the need for adjustment work, then their extraordinary performance will certainly not be superfluous.

Carburetor adjustment on lawn mowers and lawn mowers. Setup instructions with step-by-step description

The process of adjusting the carburetor of a lawn mowing machine or trimmer is not difficult, however, its implementation should occur step by step with the recommendations. Before starting work, it is necessary to carry out preparatory actions, namely:

Flushing the engine is advisable, but not necessary.
Check the spark plug and, if necessary, clean it, measure the clearance and replace. Do not forget that candles have their own resource, and are consumables. Sometimes the unstable operation of the internal combustion engine can be connected precisely with the malfunctioning of the candle
Check if the carburetor is properly attached to the cylinder-piston group, as the fastener very often loosens (or the gasket wears out), which leads to air leakage or primer. After tightening and replacing the gasket, the carburetor may not even need to be adjusted
Check the condition of the connecting adapter, which is between the carburetor and the CPG
Clean or replace the air filter. It all depends on the state of the filter element. If the element is suitable for use, the filter can be washed in soapy water, then dried and continued to operate.
Fasten the spool or cutting knives to the tool spindle. Adjustment is carried out under load, even if insignificant

When all the preparation points are completed, we proceed to the direct process of setting up the carburetor. First you need to start the engine, and let it run for 5-10 minutes, depending on the ambient temperature. When starting the motor on the XX coil or knives on the trimmer should not rotate. If they move, then it is necessary to reduce idle speed. The photo below shows an example of the location of the adjusting screws that make the adjustment.

Using a slotted or Phillips screwdriver, we proceed to the direct process of tuning work. First, we reveal the number of screws for tuning, since there can be 2 or 3, which depends on the tool manufacturer. Typically, Chinese trimmers are equipped with two screws. Below we consider the carburetor setup process, which has three tuning screws:

A regulator labeled L. You need to start tuning manipulations with it. It is necessary to turn the screw while the motor is running. This screw is responsible for enriching the mixture at low speeds, so it should be screwed so that it reaches its maximum value. Usually this bolt rotates all the way, and then loosens by ¼ turn. If there are dips, it is necessary to tighten the bolt again to the stop, and loosen it by 1/8
Screw marked T or LA. It is used to set idle speed. The rotation of the bolt to the right side (twisting) contributes to an increase in idling, and to the left to decrease. When the revolutions of the twentieth increase, it means that more air is added to the combustible mixture. The mixture is leaner and its power or traction is lost. Reduced revolutions on the twentieth indicate an excess of air in the mixture, so you need to find a middle ground. The setting must be done so that the lawn mowing engine runs stably on the twentieth, and the reel with fishing line or steel cutting disc does not rotate. Rotation of the cutting elements contributes to quick grip wear.
Screw marked H. This screw is responsible for setting the combustible mixture at high speeds. It is with this screw that the tuning manipulations end. The maximum speed value is indicated in the technical description of the tool. To maximally accurately determine the value of the maximum speed, you should use the tachometer. If there is no tachometer, then tuning is done by ear. As soon as the maximum speed is reached by ear, the valve must be returned half a revolution back (counterclockwise). Bolt H is responsible for power, temperature and fuel consumption

Often, it is precisely with the setting of maximum revolutions that difficulties arise. To prevent this from happening, the following actions are performed:

By pressing on the gas, it is necessary to rotate the screw until the speed decreases (clockwise or right)
After reducing the speed, it is necessary to rotate the bolt so (counterclockwise or to the left) to detect unstable engine operation
Once this unstable operation is detected, turn the screw clockwise until smooth operation of the engine
This completes the adjustment process.

It is interesting! For a more precise adjustment of the carburetor of the lawn mowers, it is recommended to use a tachometer. How to configure the carburetor using a tachometer is described in detail on the example of a chainsaw.

If the tuning work is done correctly, the tool will work stably, the cutting element will not rotate at idle, and the fuel consumption will be the same as on the new trimmer. Setting up a carburetor with two screws is much simpler, but the tuning accuracy is much lower. Typically, Chinese gasoline tools, as well as household units, are equipped with 2 screws.

Summing up, it should be noted that you can not understand the principle of operation of the membrane carburetor lawn mowers and trimmers. For tuning it is important to have a screwdriver and a tachometer. However, in order not only to adjust, but also to understand what you are doing, you need to know the design and principle of operation.

What is the problem of trimmer malfunction

Strainer There are only two difficulties with this element:

Clogging.
Breakage

In order to find out the cause of the breakdown, the fuel filter cover is unscrewed to remove the strainer. If it just accumulated dirt, then washing with gasoline or blowing will help.

With visible damage to the strainer, it is imperative to install a new one. There may also be damage on the fuel supply pipe (during repair, check this element).

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

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

The throttle body, the bundles of carburetor parts, the intake or exhaust pipe. All of these parts are subject to depressurization. Probably you can check with a simple method. Spread the problem area with soap suds.

Before adjusting, you must carefully clean the filters according to the maintenance in the annotation.

Strainer There are only two problems with this element:

Clogging.
Breakage

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

With visible damage to the strainer, it is imperative to install a new one. There may also be damage on the fuel supply pipe (during repair, check this element).

The carburetor starter in most cases does not function due to blockages. Use acetone or the same gasoline for flushing.

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

The diffuser is equipped with fuel channels. Of these, fuel is drawn in using an air stream.

Outside the carburetor is installed:

Fuel pump;
Jet system;
Fuel / air mixture control system;

Before adjustment, carefully clean the filters according to the maintenance in the instructions.

Right (L). Fuel mixture adjustment for low revs.

Need to find the maximum idle speed. To do this, slowly unscrew the screw (L) to the right and left.

To adjust, turn the screw a quarter turn necessarily counterclockwise.

Lower (T). Is responsible for adjusting the engine at idle.

Clockwise. Increase;
Counterclockwise. Decrease.

For proper adjustment of idling, it is typical:

Steady work of the cold engine;
Not overestimated speed of the hot engine;
A large headroom for the trimmer head;
Stable operation of the engine when changing position (sharp rise or lowering of the knife).

Left (N). Adjustment of the mixture at high speeds. (The screw is configured last).

Setting the carburetor lawn mowers with the last screw is as follows:

Open the throttle to full, while giving out full throttle. Turn the screw clockwise until the speed drops (in this case, they are oriented by ear).
Turn the screw as slowly as possible counterclockwise until the engine runs unevenly.
Then turn back quite a bit, barely hearing stable, smooth operation.
For a more visual application of skills, it is more convenient to consider the work of an experienced user:

Interestingly, from the point of view of the author of the, the setting (its correctness) is determined by the color of the candle, and not just by the speed and stability of the engine.

The correct setting of the carburetor with your own hands in this case is the combustion of the fuel mixture without residue, the color of the candle should be light brown.

The throttle body, the bundles of carburetor parts, the intake or exhaust pipe. All of these parts are subject to depressurization. Petrol trimmer al-ko frs 4125. The carburetor of the device has a compensator. Stihl: fs 450-l. You can probably check it in a primitive way. Smear the problem area with soap suds.

The basis of the trimmer carburetor is a one-piece aluminum housing. Below is a diagram of this unit.

At the bottom of it is a diffuser, which is also called a Venturi nozzle (18). Air is sucked in by the motor through this nozzle.

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

The device operates as follows.

A vacuum is created in the diffuser during the suction stroke. This fact causes air leaks. The amount of air entering the carburetor chamber, as well as the engine power and the number of revolutions depends on the position of the throttle valve (9).
At this time, fuel from the chamber (16) is sucked through the jets (11,12), after which it is mixed with the flowing air. Gasoline, mixed with air, begins to spray. Thus, an air-fuel mixture is created.
The finished mixture enters the cylinder, where it is compressed by a rising piston and ignites at its correct point from the spark generated by the spark plugs.
Since the volume under the control membrane (18) is connected to atmospheric air through the channel (19), the membrane 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 membrane (18) returns to its original position, and the valve (14) closes.

Thus, using 3 adjusting screws, it is possible to achieve maximum engine performance, as well as to configure its uninterrupted operation at any ambient temperature, and even in mountainous areas.

A common malfunction that “chases” the fuel pump is deformation of the pump diaphragm. For this reason, it does not fit properly and the pump channels are not sealed.

The causes of membrane deformation can be as follows:

Long operation of the trimmer;
Use of unsuitable fuel;
Gas entering the pulse channel.

As a result, damage to the membrane reduces the performance of the pump, and as a result:

There is a depletion of the combustible mixture;
Difficulty starting the engine;
There are interruptions in the motor;
The piston is damaged.

Also, the aforementioned consequences for the engine can cause clogging of the pump cavity on the pulse side. In this case, dirt enters the membrane through the pulse channel.

To eliminate clogging, you will have to disassemble the carburetor and clean the membrane.

Carburetor Repair for STIHL FS55 Lawn Mowers

Replacing the o-ring, accelerator in the carburetor of the lawn mowers (gas trimmer) STIHL FS55.

Stihl FS 55. Carburetor adjustment (idle)

We adjust the trimmer carburetor Stihl FS 55 in the in order to adjust the idle speed.

Fuel is sucked into the carburetor system by a pump (its membrane). Then it passes through the fitting in the carburetor. Further, the fluid moves through the inlet and outlet valves of the pump. Adjustment and repair of the carburetor lawn mowers trimmer stalls at full throttle. Stihl fs 55. Filtered by mesh. The needle valve moves into the membrane chamber.

Air supply to the tube with an air baffle (damper). The partition controls the intensity of the air flow.
The fuel supply system must be narrowed by a diffuser to increase the flow rate.
Gasoline through the float chamber and nozzle tube with narrowing. A camera with a float adjusts the temporary volume of gasoline. How to start a cold gasoline trimmer Stihl fs-55 correctly. Carburetor adjustment. In the float chamber, the pressure level is neutral, and in the tube with narrowing is already low. Due to the pressure drop, fuel enters through the nozzle.
The acceleration of the air flow contributes to the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the necessary proportion or density is formed.
The air-fuel mixture enters the engine cylinder through the fuel pipe.

Carburetor adjustment of Chinese lawn mowers. Practice.

The correctness of the carburetor option is determined by the operation of the engine and the color of the candle. Adjusted.

Carburetor adjustment of lawn mowers in practice

Carburetors for lawn mowers can be purchased here: How to adjust the carburetor, if configured.

Carburetors for lawn mowers can be purchased here: How to adjust the carburetor, if configured

The correctness of the carburetor option is determined by the operation of the engine and the color of the candle. Adjusted

Air supply to the tube with an air baffle (damper). The partition controls the intensity of the air flow.
The fuel supply system is certainly narrowed by a mixer to speed up the flow.
Gasoline through the float chamber and nozzle tube with narrowing. A camera with a float adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with narrowing is already small. Due to the pressure drop, fuel leaks through the nozzle.
The acceleration of the air flow contributes to the transfer of fuel (gasoline) and its atomization. Ultimately, an air-fuel mixture of the desired proportion or density appears.
The air-fuel mixture seeps into the engine cylinder through the fuel pipe.

A carburetor is a power supply module in which liquid fuel and air are mixed before being fed into the engine cylinders. Depending on the tool and its operating mode, mixing and feeding are adjusted accordingly.

The carburetor device for lawn mowers is the same in almost all cases. It belongs to the category of float devices. The latter provide stable parameters of the finished mixtures.

The principle of operation of the module is as follows.

Air enters the body of the tube with an air damper. The latter enhances or reduces airflow depending on its position.
In the area where the hole for supplying gasoline is formed, the tube has a constriction. A diffuser. Here the flow rate increases.
Fuel from the float chamber through the nozzle is fed into the tube. The float level determines the amount of fuel supplied. Since the pressure in the chamber is normal and low in the tube due to the greater dilution of air, gasoline is sucked through the nozzle.
Accelerated airflow picks up fuel and atomizes it, forming an air-fuel mixture of the desired density.
The mixture is sucked into the cylinder through a pipe.

The more open the air damper in the tube, the higher the density of the air flow, which means that more fuel enters the cylinder. Setting the carburetor of the lawn mowers is reduced to setting such a ratio of dampers at which the density of the fuel mixture becomes optimal.

The air flow entering the tube with a throttle is amplified or weakened depending on its position. From the fuel chamber, gas enters a special pipe through the nozzle. Float. A device that regulates the supply of fuel, its level determines the volume. Gasoline supplied through the nozzle is mixed with air under the influence of a pressure difference. This produces an air-fuel mixture for engine operation.

Note! Improper fuel composition is due to a lack of gasoline or air. This means that you need to adjust the throttle or the position of the float. The motor may also stall due to the jet, but this is already a more serious failure.

Carburetor Adjustment Lawn Mowers

The correctness of the carburetor option is determined by the operation of the engine and the color of the candle. Adjusted.

Carburetors for lawn mowers can be purchased here: How to adjust the carburetor, if configured.

Carburetors for lawn mowers can be purchased here: How to adjust the carburetor, if configured

The correctness of the carburetor option is determined by the operation of the engine and the color of the candle. Adjusted

We adjust the trimmer carburetor Stihl FS 55 in the in order to adjust the idle speed.

The motor may stall immediately after it has been started. The reason is that gasoline is not supplied enough. This is called “poor” fuel;
Excessively supplied gasoline leads to incomplete combustion, excessive mixture density and uneconomical consumption.

Important! It is necessary to regulate the carburetor under different circumstances: changes in temperature, octane number of fuel or type of oil, after winter or at the end of the break-in period, load or spontaneous cranking of screws from strong vibration of the case. Some owners prefer to configure the module before each use to make sure that it works correctly.

Note! A float carburetor has been used for decades, and the main problems are similar for all types. The principle of operation of the device depends on the quality of the mixture, and the adjustment is aimed at ensuring it.

L. For fuel supply of a low-speed mode;
H. Fuel supply at high speeds and its consumption;
T. Idle debugging.

Adjusting the lawn mowers, whose production is Chinese, can cause difficulties due to the presence of only one screw, which is responsible for idling.

Important! The answer to the question of how to adjust the Champion lawnmower carburetor is better to look at the where the professional does it.

After proper adjustment, the engine must increase speed, and when idling, the cutting tool will not turn. Everything is easy and simple!

Carburetor adjustment is necessary in the following cases:

The new engine was tested (4-5 liters of fuel mixture were used);
Fuel composition has changed (brand of oil and gasoline);
The weather has changed (it has become hot, cold);
Rarefied air (applies to mountainous areas);
After prolonged storage;
Increased engine load (after changing tools, etc.);
Due to vibration, the adjustment screws spontaneously unscrew;
Increased fuel consumption, carburetor overfills fuel;
Carbon deposits quickly appear on the spark plug electrodes (while the fuel mixture is prepared correctly);
The engine starts and immediately stalls or picks up poorly;
No gas enters the cylinder;
A large amount of exhaust gas.

Before setting up the trimmer carburetor, 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, squeeze it out and let it dry well).

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

So, turn the idle speed control to the left, until the trimmer head stops completely.

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

The right knob L adjusts the level of enrichment of the combustible mixture at low speeds. It needs to be regulated first. Get maximum idle speed. This is done using the L knob, turning it left and right. After finding the point of maximum revolutions, return the regulator half a turn to the left (counterclockwise).
The lower T (LA) knob is used to adjust the idle speed. By turning it to the left, the engine speed will begin to decrease, and when you turn the regulator to the right, the speed will increase.
The left regulator H is responsible for the enrichment of the combustible mixture at high speeds. The enrichment setting completes the carburetor adjustment. Also, using this controller, you can adjust the maximum speed, fuel consumption and engine power.

Source

Lawn mowing carburetor is a unit in the power system. In it, like any carburetors, there is a process of mixing air and fuel (gasoline) for further supply to the engine cylinders.

The main problems and malfunctions of the carburetor.

Strainer There are only two problems with this element:

Clogging.
Breakage

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

With visible damage to the strainer, it is imperative to install a new one. There may also be damage on the fuel supply pipe (during repair, check this element).

The carburetor starter in most cases does not function due to blockages. Use acetone or the same gasoline for flushing.

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

The device of the carburetor lawn mowers

The diffuser is equipped with fuel channels. Of these, fuel is drawn in using an air stream.

Outside the carburetor is installed:

Fuel pump;
Jet system;
Fuel / air mixture control system;

The principle of the carburetor lawn mowers

The throttle valve determines the amount of air for supply, and engine power directly depends on this.

Phased operation of the device:

Air supply to the tube with an air baffle (damper). The partition controls the intensity of the air flow.
The fuel supply system must be narrowed by a diffuser to increase the flow rate.
Gasoline through the float chamber and nozzle tube with narrowing. A camera with a float adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with narrowing is already low. Due to the pressure drop, fuel enters through the nozzle.
The acceleration of the air flow contributes to the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the necessary proportion or density is formed.
The air-fuel mixture enters the engine cylinder through the fuel pipe.

Source

Grass Trimmer adjustment, idle, trimmer, video