Do it yourself lawn mower carburetor adjustment

Table of Contents:

Defective fuel pump

The most repetitive breakdown is wear and tear of the diaphragm. As a result, its non-conformity. The fuel passages are not sealed at certain stages in the engine cycle. The reasons are as follows:

  • you have been working on the brushcutter or trimmer for too long without interruption;
  • fueled with low-quality fuel;
  • exhaust gases enter the impulse channel.

A deformed membrane is fraught with several bad consequences:

  • there is not enough gasoline or oxygen in the generated combustible mixture;
  • the motor starts after 10 or more unsuccessful attempts;
  • the engine knocks, clinks during operation, etc.;
  • the working piston is deformed.

As a result, the inner space of the fuel pump becomes contaminated from the side of the impulse channel.

Broken primer

Primer is a mini hand pump for forced pumping of fuel into the carburetor. For a successful start of the engine, it may be necessary to pump 20 ml of gasoline manually.

Adjustment diaphragm damaged

The membrane often deforms (sometimes breaks) due to the continuous operation of the brushcutter or grass trimmer for several hours. If you abuse this “shock” mode of operation, membrane damage occurs more often. New breakdowns will sprinkle like a cornucopia:

  • the piston will break;
  • the number of unsuccessful engine start attempts will increase dramatically;
  • the fuel mixture contains too little gasoline;
  • useful (thermal) power will sharply drop.

Strainer clogged

Reasons for blockage of the mesh filter. poor quality fuel cleaning, damage to the hose and / or delivery head.

How to adjust the carburetor of a lawn mower?

a lawn mower or grass trimmer, despite its relative simplicity (compared to a car engine), sooner or later fails. There comes a time when long downtime and restarts of the gasoline unit cannot be avoided. maintenance is needed. In advanced cases, repair is required, or rather, replacement of worn-out parts with the same new ones. Until you are faced with the need to replace your spent parts, carburetor maintenance is required. cleaning, rinsing, reconfiguring mechanisms.

Damper worn out

The throttle and air damper become unusable due to the ingress of dust, metal particles, etc. with the air flow. Damaged dampers are similar to parts that have been blasted with sand. Due to wear on the dampers, the efficiency of the motor decreases, and breakdowns are detected. Piston and cylinder wear out.

The dampers become unusable due to improper maintenance of the air filter or its breakdown.

In some cases, this filter is simply not suitable for your brushcutter or grass trimmer model. In the end, the motor shaft will suffer. its pieces fall into the engine channels, which will cause the piston to be broken.

Carburetor cannot be adjusted

The fact that the adjustment is too coarse (it is not possible to accurately set the parameters) are to blame for the springs on the adjusting screws. A brushcutter or grass trimmer manufacturer may supply unnecessarily thick and stiff springs. Others can be found either in workshops where similar equipment is repaired, or purchased from any dealer or official representative of the company that produced the motor for your grass trimmer or power scythe.

Lawn Mower Carburetor Device

The standard design of any gasoline grass trimmer necessarily includes a fuel system, the basis of which is the action of a regular carburetor. Its structure and initial principle of operation are almost the same for all brushcutters, regardless of their design features and purpose.

The brushcutter carburetor consists of an all-metal aluminum body that protects the internal components of the unit from moisture, fine debris and dust. In the lower part of the body there is a built-in diffuser, 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 unit to enrich the fuel. A diffuser works according to a simple principle: the smaller its diameter becomes, the more intensively the air is sucked in. This is due to the fact that in the area 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. The rest of the carburetor parts: standard adjusting screws and a fuel pump, can be located both inside and outside the carburetor.

The device of the carburetor of the brushcutter includes a throttle valve, the main task of which is to regulate the volume of intake air. The larger the amount of air, the higher the power rating of the grass trimmer. Another function of the damper is to facilitate cold starting of the engine. If the mower is starting up for the first time after a long period of inactivity, the shutter must be closed. Immediately after starting the engine, the part must be opened, otherwise the internal combustion engine will stall.

The grass trimmer carburetor is equipped with an impulse channel that connects the internal cavity of the engine crankcase with the impulse chamber of the pump. The piston located in the engine cylinder creates reciprocating movements, which leads to gradual changes in pressure inside the crankcase. At the same time, the membrane is set in motion. Thus, the action of the pump is fully synchronized with the operation of the power unit.

The diaphragm of the standard carburetor takes an active part in the suction of fuel. It enters the fuel unit through the fitting. The fuel then passes through the integrated inlet and outlet valves, then through the strainer and fuel pipe. The fuel then flows next to the needle and gradually fills the chamber equipped with the control diaphragm.

The stock trimmer carburetor valve is connected to the diaphragm using a lever. Below the built-in membrane there is a cavity into which air is sucked in through a special opening.

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

When the carburetor setting of the household grass trimmer is required?

Adjust the built-in grass trimmer carburetor when:

  • running in a new engine, during which 4 to 5 liters of fuel mixture were used;
  • sudden changes in the weather;
  • changes in the air pressure. for example, when the mower is often used in mountainous areas;
  • long-term simple grass trimmer;
  • intensive growth of loads on the power unit of brushcutters;
  • arbitrary unscrewing of the built-in adjusting screws of the carburetor. this causes increased vibration of the internal combustion engine;
  • changes in the quality of the components of the fuel mixture;
  • pouring fuel with a carburetor, resulting in an increase in fuel consumption;
  • the regular appearance of a thick layer of resinous deposits and carbon deposits on the surface of the electrodes of the standard spark plug for the grass trimmer;
  • starting the engine and its arbitrary shutdown or slow set of revolutions;
  • lack of fuel flow into the cylinder of the power unit;
  • increase in the volume of emitted waste gases.

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

Carburetor for grass trimmer: device, do it yourself setting

The stable and efficient operation of a domestic grass trimmer is largely dependent on the quality of the fuel used by the operator. The filled fuel mixture must be enriched with air. a built-in carburetor is responsible for this in the basic device of the brushcutter. This knot is one of the main elements of the grass scythe, so the operator must constantly monitor its serviceability and settings. Otherwise, the grass trimmer will lose its performance and may be completely damaged.

Do-it-yourself lawn mower carburetor adjustment

Periodic adjustment of the grass trimmer carburetor must be performed with a serviced and fully functional power unit. Before starting the procedure, the operator must thoroughly rinse the internal combustion engine parts and inspect its CPG for burrs or other defects. In addition, you will need to clean or change the spark plug, as well as rinse the filter elements in the brushcutter design.

When adjusting the carburetor, the mower‘s engine must be running under a certain load. It is best to install a cord of the appropriate diameter or cutting blades on the grass trimmer.

After installing the cutters, the operator should start the engine of the grass trimmer and let it run for about 10 minutes. If, during the operation of the power unit at idle, it was noticed that the cord or knife rotated, then it is necessary to reduce the speed generated by the motor. To do this, turn the lower adjuster, often marked with the letter “T”, to the left, until the installed cutter comes to a complete stop.

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 when the engine is running at low revs. The position of this screw must be adjusted first. To do this, the operator will need to achieve maximum engine speed when idling. to do this, turn the screw “L” one by one to the right or left. As soon as the maximum speed is reached, the screw will need to be turned 1/2 turn to the left;
  • The screw “T” or “LA” is required to adjust the idle speed. While turning it to the left, the speed of the power unit will decrease, and when turning to the right, it will increase accordingly;
  • The “H” regulator on the left is responsible for enriching the fuel mixture with air when the internal combustion engine of the grass trimmer is operating at high rpm. This screw is also needed to adjust the engine power and the amount of fuel consumed. Its position is adjusted by turning the screw to the right or left side until the maximum permissible engine speed is reached. After that, the screw “H” will need to be turned 1/2 turn to the left.

Signs of imbalance

Debugging the carburetor must be done during the manufacture of the device. As a rule, the owners will find out about the need to adjust the fuel supply with their own hands only after serious enough breakdowns, in the process of correcting which, the module was removed and, for example, cleaned.

Signs of a configuration failure are the following:

  • starts, but the engine immediately stalls. since the engine can only work when a certain amount of gasoline is supplied, with too “lean” fuel, that is, blocking the supply channel, the engine will stop;
  • too high fuel consumption, a lot of exhaust gases. the result of incomplete combustion of the mixture. In this case, on the contrary, there is too much fuel and the mixture is too dense.

The carburetor for lawn mowers from STIHL, Makita, Husqvarna and others is adjusted using the adjusting screws. Sometimes the reason for the malfunction is a violation of fixation. due to vibration or damage to the protective cap. Such a breakdown can be detected by simply trying to turn the screw slightly: if the fixation is not rigid, it is worth checking the setting.

Lawn mower carburetor adjustment and repair

The grass trimmer does not belong to complex household appliances, therefore, most of its breakdowns are mechanical in nature and are quite successfully eliminated with their own hands. Even if the engine fails for serious reasons. damage to the piston ring, for example, repairs are reduced to replacing a part.

Read more:  Adjusting The Chainsaw "Husqvarna" Carburetor.

But even with a relatively simple design, such a part of the device as a carburetor needs to be adjusted.

Principle of operation

The carburetor is a power system module in which liquid fuel and air are mixed before being fed into the engine cylinders. Mixing and flow are adjusted accordingly depending on the tool and its mode of operation.

The carburetor design of a lawn mower is the same for almost all cases. It belongs to the category of float devices. The latter provide stable parameters of ready mixes.

  • Air enters the body of the air damper tube. The latter increases or decreases the air flow depending on its position.
  • In the area where the hole for the gasoline supply is formed, the tube has a narrowing. a diffuser. Here the flow rate increases.
  • Fuel from the float chamber is fed through the nozzle into the tube. The float level determines the amount of fuel supplied. Since the pressure in the chamber is normal, and in the tube it is low due to the greater rarefaction of the air, gasoline is sucked in through the nozzle.
  • The accelerated air flow picks up the fuel and atomizes it, forming an air-fuel mixture of the desired density.
  • The mixture is sucked into the cylinder through the pipeline.

The more open the air damper in the tube, the higher the density of the air flow, and, therefore, more fuel enters the cylinder. Adjusting the carburetor of a lawn mower is reduced to setting such a valve ratio, at which the density of the fuel mixture becomes optimal.

Do-it-yourself lawn mower carburetor adjustment

Setting up the module does not apply to repair and replacement of spare parts is not required. In this case, you will not need a lawn mower carburetor repair kit.

  • L. is regulated first, since it is responsible for supplying fuel at low speeds;
  • H. he is responsible for the supply of gasoline at high speeds, as well as for fuel consumption and temperature;
  • T. it is used to debug idle.
yourself, lawn, mower, carburetor, adjustment

There are options, as a rule, this is the carburetor of a Chinese lawn mower, when only one screw remains on the body for debugging. for adjusting the idle speed. This does not mean that the module is configured automatically. it means that it will be difficult to carry out even such a type of repair as debugging. In the photo. adjusting the carburetor of a Chinese lawn mower.

  • The module is configured only when the engine is warm: for this, the device is pre-switched on for 10 minutes. If the mowing head rotates at idle speed, then the debugging starts immediately: turn the screw T counterclockwise until the rotation stops.
  • Adjustment begins with screw L. The screw is turned to the right and left until it finds such a position at which idle speed does not become maximum.
  • Then the screw is turned ¼ turn counterclockwise. This will be his working position.
  • Idle speed must be adjusted by turning counterclockwise to increase the number of revolutions and clockwise to decrease it. Its debugging consists in achieving such a mode in which a sufficient number of revolutions are made before the start of rotation of the mowing head. In this case, the engine must work stably at different positions.
  • The L screw position is determined last. the grass trimmer should not operate at maximum speed for more than 10 seconds. The throttle opens, the screw turns clockwise, very slowly, until the decrease in the number of revolutions is audible.
  • Then, also slowly, the screw rotates counterclockwise until the motor starts to malfunction. Then the screw is turned back clockwise until the engine starts working normally again.

If there is a tanometer, and if the recommended rpm values ​​are indicated in the product passport, the correction can be made more accurate, focusing not on hearing, but on the readings of the device.

The adjustment of the carburetor of the lawn mower in the video was carried out by ear.

8 Комментарии и мнения владельцев on the post “Adjustment and repair of the carburetor of the lawn mower”

Please clarify. In the adjustment section p. 5, screw L. error? Should you read screw A? Thank you.

prompt the initial position of the screws H L LA

prompt the initial position of the screws H L LA

Thank you very much for the video about the accelerator and did not know, but the defect is very important and creates a huge problem that almost everyone is silent about. BRAVO….

Maybe all the same tachometer is a rpm meter, and not a tonometer blood pressure meter

The video shows some kind of tightness, so you need to be able to chew snot.

Do-it-yourself lawn mower carburetor adjustment

Sometimes, for the good operation of a device, it is not required to repair one or another part, replace it, or worse, replace the device itself. Sometimes it is enough to understand the principle of its operation and configure it correctly. For example, the carburetor of a lawn mower can be adjusted to avoid high fuel consumption or more serious problems.

Lawn Mower Carburetor Device

A gasoline lawn mower, as the name suggests, is powered by an internal combustion engine that uses gasoline as fuel. In order for it to burn inside, air is required to form a reaction. The latter creates thermal energy, which then turns into mechanical.

To supply fuel with air into the engine cylinder and use a carburetor.

First, gasoline mixed with oil is transferred to the float chamber. There it continues its flow further, but when the required level is filled with fuel, the float rises, shutting off the fuel supply valve. The jet is a plug that prevents fuel from flowing out of the float chamber.

Gasoline flows into the mixing chamber, from above which air is supplied. The throttle blocks the access of fuel to enter the cylinder. When you press the mower pedal, it opens, and fuel is supplied inside, and the internal combustion engine picks up speed. The maximum throttle valve can rotate up to an angle of 90 degrees, which depends on the force of pressing the gas pedal. A vacuum is formed in the mixing chamber, a strong air flow mixes with the fuel and transfers it to the cylinder.

At low speeds, an idle system is used, in which the throttle does not open completely, but partially.

The carburetor filter cleans the fuel from dust and other small elements, protecting the nozzles from their harmful effects. If they are clogged, the motor power will be noticeably reduced.

The task of the carburetor is to quickly direct the fuel to the cylinder with the help of air, mix it with oxygen, which allows gasoline to burn. The difference between an automobile carburetor and a trimmer is only in the presence of a membrane in the latter, which is used to suck gasoline from the tank.

How to tell if your lawn mower carburetor needs adjustment

This may be evidenced by the following signs:

  • Difficult starting of the engine, weak set of revolutions.
  • Increased fuel consumption.
  • Engine runs unstable, rpm jumps frequently.
  • There is a large amount of exhaust gas.

Checking the spark plug can help you determine if the carburetor is properly adjusted. First, we release it from the casing, disconnect the contacts from the igniter.

We clean the nest of the candle with a device that blows air. A compressor with a small tube is perfect for this purpose. Using a torque wrench, remove the candle.

After pouring a solvent for washing the threads into the socket of the spark plug, after a short period of time we unscrew the plug to the end. If the electrodes are black, then this is carbon deposits, which are associated with poor carburetor adjustment. If it is of a brick shade, then everything should be in order with the gas cutter.

After a long period of inactivity, the tool also needs adjustment. For example, after winter.

It is also recommended to carry out the adjustment when changing the composition of the fuel mixture: oil or gasoline.

Adjustment

  • We start the engine. When you start it on XX, the knives should not rotate, if the opposite happens, then we reduce the idle speed.
  • We adjust the screw L. It is responsible for the mixture at low revs. First, we scroll clockwise until it stops, then unscrew it 90 degrees counterclockwise. If gaps are found, we repeat this action, weakening it by 1/8, that is, by 45 degrees.
  • We adjust the screw LA, the more common name is T. With an increase in the speed of XX, more air is added to the mixture. Power is lost. But if there is not enough air, the fuel is burned worse. We unscrew the screw so that it works perfectly at low speeds, while the knives should not rotate. In the process of tuning, you need to feel the speed, it should work stably at XX.
  • We adjust the screw H, which adjusts the mixture at high rpm. To identify their maximum number, we use a tachometer. When the maximum number of revolutions of the internal combustion engine is reached, we unscrew the screw to the left by 180 degrees, the adjustment is over.

Sometimes only the correct setup and use of the device reveals its full potential. You do not need to neglect it and carry out as needed.

Adjusting the carburetor after replacing it

Even with an exact match to the make and model of the car, after replacing the old carburetor with a new one, it will need to be adjusted. The fact is that engine characteristics such as the degree of vacuum in the cylinder at the intake stroke change over time.

What can we say about installing a carburetor on an engine that is not normally intended for use with another model of the device. In such cases, in addition to knowledge and experience, special equipment is often required: gas analyzers, stroboscopes, a measuring tool.

The adjustment is carried out in stages, and the settings are checked at various engine operating modes and are more likely to be done by professionals than ordinary motorists.

Nevertheless, you can try to make a number of adjustments to the standard carburetor that can make fuel consumption more economical and help to make the car more powerful in high-load modes.

In addition to the already mentioned adjustments for the quality and quantity of the fuel mixture and the fuel level in the float chamber, these can be the following operations:

  • Adjustment of the air damper actuator: when the choke handle is fully recessed, the damper must be fully open.
  • Adjustment of the throttle valve drive: when the gas pedal is depressed to the end, the throttle must be fully open.
  • Adjusting the carburetor starting device: setting the normalized gaps between the edges of the air and throttle valves and the walls of the mixing chamber.
  • Correct installation of the electromagnetic valve (EMC): when removing the wires from the EMC (the needle valve closes the idle channel), the engine should stall.

Features of settings and adjustments of carburetors depend on the specific model of the device and the parameters of the car engine, therefore, when working independently, you should first of all be guided by the manufacturer’s technical documentation.

Principle of operation

The carburetor is a power system module in which liquid fuel and air are mixed before being fed into the engine cylinders. Mixing and flow are adjusted accordingly depending on the tool and its mode of operation.

The carburetor design of a lawn mower is the same for almost all cases. It belongs to the category of float devices. The latter provide stable parameters of ready mixes.

  • Air enters the body of the air damper tube. The latter increases or decreases the air flow depending on its position.
  • In the area where the hole for the gasoline supply is formed, the tube has a narrowing. a diffuser. Here the flow rate increases.
  • Fuel from the float chamber is fed through the nozzle into the tube. The float level determines the amount of fuel supplied. Since the pressure in the chamber is normal, and in the tube it is low due to the greater rarefaction of the air, gasoline is sucked in through the nozzle.
  • The accelerated air flow picks up the fuel and atomizes it, forming an air-fuel mixture of the desired density.
  • The mixture is sucked into the cylinder through the pipeline.

The more open the air damper in the tube, the higher the density of the air flow, and, therefore, more fuel enters the cylinder. Adjusting the carburetor of a lawn mower is reduced to setting such a valve ratio, at which the density of the fuel mixture becomes optimal.

Read more:  How to Change the Head on a Gasoline Lawn Mower

Adjusting the carburetor of the lawn mower, grass trimmer

Check if the Start button is on, if the supply button has enough oil, if gasoline is poured into the tank. If the engine still does not start, flush the gas filter (sometimes it should be replaced if a large blockage is found), check the plug for operability, clean the air filter.

It did not help? Adjust the carburetor choke to position C, this solves the fuel overflow problem. If the engine is “stubborn”, simply drain all fuel from the system and refill with new, making sure that it is of the proper quality. Doing all these processes solves the problem of starting the motor in 80-90% of cases.

If the engine refuses to idle, first of all adjust the carburetor and flush the air filter of the device. this in most cases solves the problem. If the situation repeats itself, then most likely you have poured bad fuel into the fuel tank, then drain it and fill the tank with new.

How to start a lawn mower and make it work if the engine does not pick up speed and it stalls? First, check to see if the cutting shaft is clogged with grass and weed debris. If everything is in order with the shaft, wash the air filter or replace it with a new one if the first one seems too dirty to you. By the way, the air supply filter should be washed with detergent and gasoline, which makes the gasket more elastic and prevents the material from drying out.

If, after completing these procedures and pressing the lawnmower starter, the lawnmower stalls again, then the matter lies in an incorrectly adjusted carburetor device. Read the last section of this article, it describes how to adjust the carburetor on a petrol cutter.

If there is no spark, put in a spare spark plug to check what exactly is the matter. When the spare candle, when setting the correct gap, also does not produce a spark, then it is a matter of equipping a scythe for grass. Repairing a lawn mower in the event of a malfunction begins with checking the wire leading to the candle.

Adjusting the carburetor of a Chinese lawn mower. In this video I will show you how to adjust the carburetor on the trimmer and how to adjust. Practice.

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

Fuel is sucked into the carburetor system by a pump (its membrane). The video will help to change the ignition on the trimmer, the ignition on the trimmer can be changed independently, for this you do not need any special devices and devices. I will show how simple and. Then it goes through the choke in the carburetor. Then the liquid moves through the inlet and outlet valves of the pump. Filtered by the grid. Moves through the needle valve into the diaphragm chamber.

  • Air supply to a tube with an air baffle (damper). The baffle regulates the intensity of the air flow.
  • The fuel supply system is necessarily narrowed by the mixer to accelerate the flow.
  • Gasoline through the float chamber and the nozzle tube with a constriction. How to clean a carburetor on a trimmer a candle, not how to change a coil on a trimmer. A float chamber adjusts the temporary volume of gasoline. How to clean a muffler on a Husqvarna 128 r trimmer very often the problem of power loss lies on the surface and people, without knowing it, try to change the carburetor to a Husqvarna be. In the float chamber, the pressure level is neutral, and in the tube with a constriction it is already small. Due to the pressure drop, the fuel seeps through the jet.
  • The acceleration of the air flow assists in 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.

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

Simply put, adjusting the carburetor on a petrol cutter. creating a good fuel consistency due to the correct air supply.

We adjust the Husqvarna carburetor if:

And also to make sure the Husqvarna engine is running as expected and that the grass trimmer (lawn mower, brushcutter) is at its maximum efficiency.

Causes of carburetor breakdowns

When using brushcutters (for example, “Patriot” or “Soyuz”), the carburetor may be damaged, and the user will need to repair it on his own or with the assistance of specialists. This can happen for a number of reasons. One of the most common is non-compliance with the rules for using the device. If, during prolonged operation of the grass trimmer, maintenance and adjustment of the carburetor have not been carried out, the device breaks down.

Another reason for the breakdown is an improperly prepared fuel mixture. Often, equipment owners buy oil and prepare fuel according to the recommendations written on the packaging of fuels and lubricants, which is incorrect. When preparing fuel, you must take into account the operating instructions for the brushcutter itself. In addition, you should not make the mixture “by eye”, as incorrect proportions also lead to equipment breakdown.

Most of the breakdowns of carburetors are equally typical for brushcutters of different brands, be it Echo, Kedr, Homelite or a device from another manufacturer.

How to sharpen a knife or disc for a mower?

To sharpen a cutter blade or blade, know that a good blade or blade must be sharpened so that the edges are sharp without overheating the metal. A sharpened cutting element will make it easier to remove the grass surface. Also, the sharpness of the disc or knife affects the number of plants that will be removed with one grab.

In general, maintenance of a gasoline scythe for grass involves constant cleaning of equipment after work, checking the quality of oils and gasoline, as well as a properly tuned carburetor. Do not put questionable additives and the like into the mower. Regularly lubricate the gearbox and lubricate the driving elements to prevent malfunctions. The lubricant is recommended to be renewed at least every 1000 hours of operation.

Do-it-yourself lawn mower carburetor adjustment

A lawn mower carburetor is an assembly 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 the carburetor is regulated.

Lawn Mower Carburetor Working Principle

The throttle valve determines the amount of air to be supplied, and the engine power directly depends on this.

Fuel is sucked into the carburetor system by a pump (its membrane). Then it passes through the choke in the carburetor. The fluid then flows through the pump inlet and outlet valves. Filtered by the grid. Moves through the needle valve into the diaphragm chamber.

  • Air supply to a tube with an air baffle (damper). The baffle regulates the intensity of the air flow.
  • The fuel supply system is necessarily narrowed by a diffuser to increase the flow rate.
  • Gasoline through the float chamber and the nozzle tube with a constriction. A float chamber adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with a constriction it is already low. Due to the differential pressure, the fuel penetrates through the nozzle.
  • The acceleration of the air flow facilitates the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the required 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 throttle is open, the greater the fuel consumption and power.

Simply put, adjusting the carburetor on a petrol cutter. creating an optimal fuel mixture due to the correct air supply.

The main problems and malfunctions of the carburetor.

Mesh filter. There are often only two problems with this element:

In order to find out the cause of the breakdown, the fuel filter cap is unscrewed to remove the strainer. If dirt simply accumulates 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 repair, they practice checking this element).

Blowing out clogged carburetor parts with compressed air is an acceptable and convenient repair practice.

The throttle body, the places where the carburetor parts are bundled, the intake or exhaust pipe. all of these parts are susceptible to depressurization. You can check for sure in a primitive way. smear the problem area with soapy foam.

Lawn Mower Carburetor Device

The base of the lawn mower carburetor is an aluminum body. It contains a diffuser (hole with inner contours). Air is blown through this hole. The flow rate of oxygen (air) depends on the cross-section (orifice) of the diffuser.

The diffuser is equipped with fuel channels. Fuel is drawn in from them using the air flow.

  • fuel pump;
  • jet system;
  • a system for adjusting the mixture of fuel and air;

How to adjust the carburetor on a petrol cutter

Before adjusting, you must thoroughly clean the filters according to the maintenance instructions in the instructions.

Further adjustment of the carburetor of the lawn mower with your own hands is done with the adjusting screws. There are three of them:

  • right;
  • left;
  • lower.

Right (L). adjusting the fuel mixture for low rpm.

You 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 of a turn, be sure to counterclockwise.

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

  • clockwise. increase;
  • counterclockwise. decrease.

How to Fix a Lawn Mower Carburetor

For the correct adjustment of the idle speed, it is characteristic:

  • stable operation of a cold engine;
  • not overestimated speed of a hot engine;
  • a large reserve of turns for the trimmer head;
  • stable operation of the engine when changing position (sharp lifting or lowering of the knife).

Left (H). mixture adjustment at high rpm. (The screw is adjusted last).

The left screw (H) determines the general adjustment of maximum speed, engine power, temperature and gasoline consumption.

Adjusting the carburetor of a lawn mower with the last screw is done as follows:

  • Open the throttle to full, at the same time give full throttle. Turn the screw clockwise until the speed drops (in this case, orientate by ear).
  • Turn the screw counterclockwise as slowly as possible until the engine runs unevenly.
  • Then turn back quite a bit, barely hearing a stable, even operation.
  • For a more visual use 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 video, the setting (its correctness) is determined by the color of the candle, and not only by the speed and stability of the engine.

Correct adjustment of the carburetor with your own hands in this case. combustion of the fuel mixture without residue, the color of the candle should be light brown.

The design of the gas trimmer carburetor and its purpose

lawn mowers are equipped with two-stroke internal combustion engines. A carburetor is used to supply the air-fuel mixture to the engine cylinder. 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 gas pump. It is due to the presence of a membrane that the considered devices in the design of two-stroke internal combustion engines are called membrane.

Structurally, the entire mechanism is a small piece with channels, valves and diaphragms inside. The carburetor body is made of aluminum, and the internal structure is shown in the photo below.

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

  • Diffuser or Venturi nozzle. through this nozzle air is sucked into the system
  • Air damper. opens and closes the filtered air supply
  • Fuel channel of maximum speed
  • Fuel channels (jets) of idle speed XX and medium speed
  • Throttle valve. the amount of opening is adjusted by pressing the gas
  • Impulse channel fitting. connects to the internal channel of the engine crankcase
  • Fuel inlet (union) (2). provides fuel supply from the gas tank
  • Membrane (4). is responsible for sucking fuel from the gas tank
  • Fuel suction valve (3)
  • The valve for supplying fuel to the carburetor channel (5)
  • Filter element (6) or fine fuel filter
  • Fuel channel (10)
  • The needle of the needle valve (14). is responsible for the supply of fuel to the chamber of the control diaphragm
  • Chamber. the fuel mixture, which is fed through the jets and the throttle valve to the cylinder
  • Control diaphragm (18). manual suction of fuel by primer is provided
  • Diaphragm Connected Lever (17)
  • Idle speed screw (15)
  • The screw for adjusting the amount of fuel supplied to the diffuser (13)
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Having an idea of ​​how the carburetor works inside, you have to figure out how it works. A detailed description of how the carburetor works on a two-stroke internal combustion engine using the example of a chainsaw is described in this material.

How does a lawn mower carburetor work or how it works

The adjustment of the carburetor of a Chinese lawn mower is completely identical with the adjustment of lawn mowers of European, Russian and manufacturers. To cope with the task of adjusting the carburetor on petrol cutters and petrol trimmers, it is necessary to understand the principle of their functioning. How the carburetor works on a petrol cutter is described step by step and accessible below.

  • The carburetor of a lawn mower begins by feeding fuel through the channel, as shown in the diagram.
  • Suction of fuel into the carburetor takes place using a pulse channel connected to the crankcase. Due to the rarefaction of air, the flexible membrane moves at number 4 in the diagram above.
  • Fuel is supplied through valves 3 and 5. Valve 3 is an inlet valve, due to which fuel is supplied to the under-membrane space, and valve 5 is an outlet
  • Further, the fuel moves through the channel and, passing through the fine filter, reaches the needle valve 14
  • The needle valve is connected by means of a lever to the control diaphragm 18
  • The needle valve is actuated by acting on the diaphragm. When it is necessary to pump fuel to start the engine, it is necessary to act on the soft cover of the hand pump. Upon exposure, the needle opens, and the chamber is filled with a fuel mixture.
  • When the engine starts (cold), the opening of the needle occurs due to the vacuum with the air damper closed. This vacuum acts through the idle and high speed nozzles on the diaphragm 18
  • The membrane acts through a 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
  • When the chamber is full, the fuel mixture is supplied (sucked in) through the idle and medium speed nozzles (when the engine is running)
  • At the same time, the throttle valve is displaced from the initial position by 10-15 degrees
  • When the work is carried out under load, the fuel begins to flow into the chamber through the high speed jet, and at the same time the throttle valve rotates through an angle of up to 90 degrees (depending on the force of pressing the gas). In all operating modes, the air damper must be open, through which the fuel is mixed with air, and thereby the mixture in the cylinder is ignited.

Below is a diagram of how a lawn mower carburetor works. Based on the diagram, you can not only figure out the principle of operation, but also identify breakdowns and other malfunctions of the mechanism.

When operating the tool, it is necessary to take into account the presence of one more jet. This jet is located between the idle and full power channels. It is necessary in order to exclude a strong depletion of the mixture, which happens when the engine is running at partial load. In such a situation, the occurrence of a badass couple is not excluded. Through an additional channel (jet), fuel is sucked into the chamber, whereby the fuel-air mixture is enriched. The diagram below shows an additional jet, which is indicated by the number 1.

Having an idea of ​​\ u200b \ u200bthe design of a diaphragm carburetor for brushcutters and the principle of operation, it will not be difficult to customize it yourself. Adjusting screws are used to adjust the carburetor of the lawn mower. The diagram above shows two adjustment screws, however most modern petrol trim models have three screws. The presence of three adjusting screws allows for more accurate adjustment, while achieving stable and uninterrupted operation of the internal combustion engine.

yourself, lawn, mower, carburetor, adjustment

How to know if your lawn mower carburetor needs adjustment

Many craftsmen use petrol cutters 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 petrol cutter or brushcutter? If you are asking such a question, then for sure 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 adjusting measures:

  • After the engine has run-in. Usually, the break-in lasts during the combustion of 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
  • When weather conditions change, however, this is more relevant for chainsaws, gas generators and motor pumps, which are operated not only in summer, but also in winter.
  • If the mower has not been used for a long time. The reason for the need for adjustment may be a winter break.
  • When fuel consumption increases
  • If black carbon is found on the spark plug electrodes
  • In the absence of gasoline entering 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 “sluggish” set of revolutions

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

The device and adjustment of the carburetor on petrol cutters and trimmers

A lawn mower or grass trimmer with an internal combustion engine requires not only constant refueling of the fuel mixture of gasoline and oil, but also periodic adjustment of the supply of this fuel. The carburetor is responsible for supplying fuel to the cylinder of the lawn mower, the efficiency and performance of the tool depend on the correct operation of which. If during operation a faulty (abnormal) engine operation is detected, then the first step is to adjust the carburetor of the lawn mower. Before setting up the carburetor of the gasoline grass trimmer, let’s first understand its design.

Adjusting the carburetor on petrol cutters and brushcutters. setup instructions with a step-by-step description

The process of adjusting the carburetor of a lawn mower or grass trimmer is not difficult, however, it should be performed step by step in accordance with the recommendations. Before starting work, it is necessary to carry out preparatory actions, namely:

  • Flush the engine. desirable but not required
  • Check the spark plug, and if necessary clean it, measure the gap and replace it. Do not forget that candles have their own resource and are consumables. Sometimes the unstable operation of the internal combustion engine can be associated precisely with the malfunctioning of the spark plug
  • Check whether the carburetor is properly attached to the cylinder-piston group, since the fastening very often weakens (or the gasket wears out), which leads to air leaks or primer. After tightening and replacing the gasket, the carburetor may not even need to be adjusted
  • Check the serviceability of the connecting adapter, which stands between the carburetor and the CPG
  • Clean the air filter or replace it. It all depends on the condition of the filter element. If the element is suitable for use, then the filter can be washed in soapy water, and then dried, and continue to operate.
  • Attach the spool or cutting knives to the tool spindle. Adjustment is carried out under load, even if it is insignificant.

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

Using a slotted or Phillips screwdriver, we proceed to the direct process of adjustment work. First, we identify the number of screws for adjustment, since there can be 2 or 3 of them, depending on the manufacturer of the instrument. Usually Chinese grass trimmers are equipped with two screws. Below is the process of tuning the carburetor, which has three tuning screws:

  • Regulator marked L. you need to start tuning manipulations with it. It is necessary to rotate the screw while the motor is running. This screw is responsible for enriching the mixture at low rpm, so it should be screwed up so that the maximum value is reached. Typically, this bolt rotates until it stops and then looses of a turn. If dips are found, it is necessary to re-tighten the bolt until it stops, and loosen it by 1/8
  • Screw marked T or LA. this is used to adjust the idle speed. Turning the bolt to the right (tightening) increases the idle speed, and to the left, decreases it. When the speed of XX is increased, this means that more air is added to the combustible mixture. At the same time, the mixture is depleted, and power or thrust is lost. Reduced revolutions at XX indicate an excess of air in the mixture, so it is necessary to find a middle ground. The setting must be done so that the lawn mower engine runs stably at XX, and the line spool or steel cutting disc does not rotate. The rotation of the cutting elements contributes to the rapid wear of the clutch
  • Screw marked H. this screw is responsible for adjusting the combustible mixture at high speeds. It is with this screw that the tuning manipulations end. The maximum speed is indicated in the technical description for the tool. To determine the maximum speed value as accurately as possible, you should use a tachometer. If there is no tachometer, then the tuning is performed by ear. As soon as the maximum number of revolutions is reached by ear, the valve must be returned half a turn back (counterclockwise). Bolt H is responsible for power, temperature and fuel consumption

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

  • While pressing the gas, it is necessary to rotate the screw until the speed decreases (clockwise or to the right)
  • After reducing the speed, it is necessary to turn the bolt so (counterclockwise or to the left) to detect unstable engine operation
  • As soon as this unstable operation is detected, the screw should be turned clockwise until smooth operation of the internal combustion engine occurs.
  • This completes the adjustment process.

How To Adjust the RPM Speed on a Lawn Mower

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

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