How to adjust the mixture on the trimmer

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 lawn mower or trimmer manufacturer may supply unnecessarily thick and stiff springs. You can find others 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 trimmer or power scythe..

Adjustment diaphragm damaged

The membrane often deforms (sometimes breaks) due to the continuous operation of the lawn mower or trimmer for several hours. If you abuse this “shock” mode of operation, membrane damage occurs more often. New breakdowns will fall 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.

Blocking the adjusting space

Deposits can build up in the control compartment. The needle does not completely close the hole, and a lot of gasoline enters the fuel chamber – the engine overflows it, possibly fills the spark plugs as well. Because of this, the gasoline-air mixture contains an increased amount of gasoline vapors. Efficiency drops noticeably.

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 lawn mower or trimmer model. In the end, the motor shaft will suffer – its pieces fall into the engine channels, causing the piston to be broken.

Principle of operation

The procedure for pumping and filtering fuel in the engine of the lawn mowers is as follows.

  • The throttle valve controls the amount of air supplied to the diffuser. The more air is supplied, the more oxygen the gasoline needs to burn, and the more power is generated in the form of heat. The heat energy is further converted into mechanical.
  • The diaphragm pump delivers the required amount of gasoline.
  • Next, gasoline passes through the engine choke.
  • Fuel flows through the intake and exhaust valves.
  • Fuel filtration is carried out using a mesh filter.
  • Through the needle valve, it also enters the chamber with the membrane.

The staging of the carburetor is as follows.

  • Air enters the duct with an air damper. The damper sets the required air flow rate.
  • In the gasoline injection unit, the diffuser is narrowed – this is necessary to give a higher air flow rate.
  • The fuel passes through the compartment with the float and bypasses the jet, enters this narrowing of the tube. The float chamber doses the gasoline supply. In this compartment, the pressure is in equilibrium. In a narrowed tube, it goes down. Due to the difference in both pressure values, gasoline and passes through the jet.
  • The accelerated flow sprays gasoline, converting it into aerosol vapors. The resulting gasoline-air mixture is ready for ignition in the combustion chamber.
  • Having passed through the fuel line, this mixture is in the carburetor cylinder.

Conclusion: to set the required power, first of all, you will adjust the rate of fuel combustion using the air damper. If the gap is too small, and oxygen in such a mixture is less than 10%, the fuel does not burn, therefore, the engine will not start or will immediately stall.

In the case of buying a Chinese trimmer, it is worth considering that it does not differ much from European ones – the same 2- or 4-stroke engine and drive.

However, they save on the quality of parts, forcing the consumer to change them more often. Check what compatible parts non-Chinese companies offer for your device.

Carburetor device

lawn mower (lawn mower) contains a base – a body made of aluminum, which houses the rest of the parts, working smoothly as a whole. There is a diffuser in the carburetor body – a stroke with internal channels through which air is pumped.

The larger the cross-section of the diffuser, the more actively oxygen is supplied together with air – an oxidizing agent, in which the fuel is burned (gasoline-oil mixture).

Channels branching off from the diffuser stroke deliver fuel, with which the forced air mixes, entraining gasoline vapors with it. Outside the main carburetor compartment are located:

  • jets;
  • mini fuel pump;
  • unit regulating the mixing of fuel with air.

The latter forms the very explosive mixture ignited in the combustion chamber of the carburetor.

Strainer clogged

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

Elimination methods

The list of upcoming work on the engine may be as follows:

  • replacement of the fuel pump;
  • disassembly and flushing of the strainer;
  • replacement of the adjusting lever;
  • it is also necessary to clean the adjustment space;
  • replacement of the membrane (or the entire block where this membrane is located);
  • adjusting the inlet, outlet and needle valves;
  • replacement of dampers;
  • cleaning fuel channels and diffuser;
  • replacement of screw springs;
  • change of primer.

Not all of this work can be done. Often it turns out that many of them are not needed if a specific malfunction is immediately detected.

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 lawn mower or trimmer for too long without interruption;
  • fueled with low-quality fuel;
  • exhaust gases enter the impulse channel.
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A deformed membrane is fraught with several bad consequences:

  • 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.

Hidden Adjusting Screws On Some Trimmers And Blowers – Video

Adjustment diaphragm damaged

The membrane often deforms (sometimes breaks) due to the continuous operation of the lawn mower or 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 drop sharply.

Blocking the adjusting space

Deposits can build up in the control compartment. The needle does not completely close the hole, and a lot of gasoline enters the fuel chamber – the engine overflows it, possibly fills the spark plugs as well. Because of this, the gasoline-air mixture contains an increased amount of gasoline vapors. Efficiency drops noticeably.

Reference. Read to understand what you are doing!

The required composition (quality) of the air-fuel mixture is adjusted (changed) by turning the screws for adjusting the fuel supply to the intake air flow (right and left). The amount of mixture supplied to the cylinder is metered by the throttle valve.
If you turn them clockwise, the mixture sucked into the cylinder becomes leaner (less fuel in the air / fuel ratio) and the engine rpm rises, while the Husqvarna engine runs softer (gains less speed) and the power drops dramatically. In addition, having increased revs, less oil is supplied to the cylinder on a lean mixture with gasoline (lubrication is worse) and so you can screw up the engine. Well, the trimmer will not start well..
If the screws are turned counterclockwise, the mixture sucked into the cylinder becomes richer (more fuel in the air / fuel ratio) and the engine speed decreases, while at low speeds more gasoline and oil gets into the cylinder (better traction, better lubrication), but the Husqvarna engine It “spins” badly (it gains momentum poorly) and more carbon deposits form in the cylinder!

adjust, mixture, trimmer

Failure of the adjusting lever

The wear of the contact edge of the lever is a consequence of an incompletely purified fuel, into which grains of sand or particles of clay, metal or other inclusions that are not soluble in liquid hydrocarbons have gotten. There is a problem with fuel injection, the engine does not function without load.

How to adjust the carburetor on a lawn mower

The upcoming do-it-yourself lawn mowers carburetor setting is done with adjusting screws. There are three of them:

Right (L) – Fuel Consistency Adjustment for Low RPM.

It is necessary to find the highest idle speed. To do this, slowly unscrew the screw (L) to the right and to the left..

To adjust, turn the screw a quarter of a turn certainly counterclockwise.

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

  • clockwise – increase;
  • counterclockwise – decrease.

For the correct adjustment of the idle speed specifically, 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).
adjust, mixture, trimmer

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.

The carburetor setting for lawn mowers 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.

do it yourself

The inlet needle is broken

The inlet needle breaks due to metal and stone particles in the gasoline. As a result, the seat of the intake needle does not fit tightly against it, the fuel mixture flows. There is too much air in the combustible mixture created by the carburetor, which can cause the engine to “sneeze” during operation. Finally, the needle may become stuck due to low-quality gasoline, or the unit has been idle for a long time..

The device and adjustment of the carburetor on lawn mowers and trimmers

a lawn mower or 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 mowers, 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 mowers. Before setting up the carburetor of the gasoline trimmer, let’s first deal with its design..


How to know if a lawn mower carburetor needs adjustment

Many craftsmen use lawn mowers for a long time without thinking about the need to adjust the carburetor of the tool. When is it necessary to adjust the carburetor on a lawn mower or lawn mower? 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
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As you can see, there are enough reasons for adjusting the carburetor for lawn mowers. 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..

How does a lawn mowers carburetor work or how it works

The carburetor adjustment of the Chinese lawn mowers is completely identical to the adjustment of the European, Russian and manufacturer’s lawn mowers. To cope with the task of adjusting the carburetor on lawn mowers and petrol trimmers, you need to understand the principle of their operation. How the carburetor works on a lawn mower is described step by step and accessible below.

  • The carburetor of lawn mowers begins with fuel supply 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 along 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 the principle of operation of the lawn mower carburetor. 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 using 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 ​​the design of the membrane carburetor for lawn mowers and the principle of operation, it will not be difficult to customize it yourself. The lawn mowers use adjusting screws to adjust the carburetor. 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.

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. Moreover, 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 that 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 mowers with your own hands, you need to deal with all the constituent elements of the device in question. The lawn mower and 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) – fuel is supplied 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) – provides manual fuel suction with primer
  • 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..

Adjusting the carburetor on lawn and lawn mowers – setup instructions with step-by-step description

The very process of adjusting the carburetor of a lawn mower or trimmer is not difficult, however, its implementation should occur step by step in compliance 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 fixed 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 use.
  • 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 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 at the same time 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 required 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.

If the adjustment 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 lawn mowers 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..