Carburetor Adjustment Of Chinese Lawn Mowers

Candle cleaning

In the worst times of trimming with an unadjusted carburetor, the engine would stop starting after every tank of fuel was used. And only after cleaning the spark plug from carbon deposits could work continue.

Fine sandpaper was used to clean the electrodes, and a thin paper clip with a bent end was used to clean the space between the insulator and the body. First, the electrodes were wiped off large dirt with a rag, then they were cleaned with sandpaper. After that, the candle was dipped into diesel fuel and the moistened carbon was scraped off with a paper clip from the surfaces of the insulator, the inside of the body and between them. Further, the candle was dipped several times into diesel fuel, which was then shaken off it along with the dirt. Sometimes the paper clip cleaning and rinsing procedure was 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 used up in less than 10 minutes 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).

Maximum speed limitation

After adjusting the fuel mixture and low speed, check how the lawn mower engine will run at maximum speed. If necessary, limit the maximum RPM to the required level with the # 3 hollow screw. Loosen the retaining nut and turn in the screw to decrease maximum RPM or turn to increase it. Tighten the nut after adjustment. The maximum RPM setting is necessary to protect the trimmer motor from overheating and to be able to use the start key lock to reduce right hand fatigue.

In the future, it may be necessary to adjust the trimmer carburetor. For example, if the engine starts to rev poorly when running at full load, loosen screw # 1 another quarter turn. If starting is difficult, increase idle speed. Both weather conditions and the quality of the fuel mixture can affect the operation of lawn mowers. Vibration can cause the adjusting screws themselves to turn.

Principle of operation

Carburetor a fuel system module that mixes liquid fuel and air before being fed into the engine cylinders. Mixing and feeding are adjusted accordingly depending on the tool and its mode of operation.

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

The principle of the module is as follows.

  • 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 gasoline feed hole is formed, the tube has a narrowing 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 sprays 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, which means more fuel enters the cylinder. Setting up the carburetor for lawn mowers is reduced to setting such a ratio of flaps at which the density of the fuel mixture becomes optimal.

From personal experience

Idle speed adjustment

We start adjusting low speed. Screw number 2 limits the return movement of the throttle lever by turning it, we increase the idle speed, unscrewing it, we decrease it. Adjust so that the engine runs reliably at low revs and even a little accelerated (for better starting), but so that the line reel or knife does not rotate, and there is a sufficient reserve of revolutions before they start to rotate. If the engine starts poorly, increase the idle speed even more.

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.

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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, if the fuel is too lean, that is, the supply channel is blocked, the engine will stop;
  • Too high fuel consumption, a lot of exhaust gases are 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 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 a car 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:

  1. Diffuser or Venturi nozzle through this nozzle air is sucked into the system
  2. The air damper opens and closes the filtered air supply
  3. Fuel channel of maximum speed
  4. Fuel channels (jets) of idle speed XX and medium speed
  5. Throttle valve opening value is adjusted by pressing the gas
  6. The connection of the impulse channel is connected to the internal channel of the engine crankcase
  7. Fuel inlet (union) (2) provides fuel supply from the gas tank
  8. Membrane (4) is responsible for sucking fuel from the gas tank
  9. Fuel suction valve (3)
  10. The valve for supplying fuel to the carburetor channel (5)
  11. Filter element (6) or fine fuel filter
  12. Fuel pipe (10)
  13. The needle of the needle valve (14) is responsible for supplying fuel to the chamber of the control diaphragm
  14. Fuel mixture chamber, which is fed through the jets and the throttle valve to the cylinder
  15. The control diaphragm (18) is provided with manual fuel suction with a primer
  16. Diaphragm Connected Lever (17)
  17. Idle speed screw (15)
  18. The screw for adjusting the amount of fuel supplied to the diffuser (13)

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.

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

A lawn mower or a 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 understand its design.

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, it is necessary to understand the principle of their operation. How the carburetor works on a lawn mower is described step by step and accessible below.

  1. The carburetor of lawn mowers begins with fuel supply through the channel, as shown in the diagram
  2. The 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.
  3. Fuel is supplied through valves 3 and 5. Valve 3 is an inlet valve, due to which fuel is supplied to the sub-membrane space, and valve 5 is an outlet
  4. Further, the fuel moves along the channel and, passing through the fine filter, reaches the needle valve 14
  5. The needle valve is connected via a lever to the control diaphragm 18
  6. 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
  7. 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 membrane 18
  8. The membrane acts through a lever on the needle valve, whereby the chamber is filled
  9. 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
  10. When the chamber is full, the fuel mixture is supplied (sucked in) through the idle and medium speed jets (when the engine is running)
  11. At the same time, the throttle valve is displaced from the initial position by 10-15 degrees
  12. 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 pressure on the gas). In all operating modes, the air damper must be open, through which the fuel is mixed with air, and thus the mixture in the cylinder is ignited
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Below is a diagram of how the lawn mower carburetor works. Based on the diagram, you can not only understand 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 another 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 a stable and smooth operation of the internal combustion engine.

How to know if a lawn mower carburetor needs adjustment

Many lawn mowers 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 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 adjustment measures:

  1. After the engine has run in. Usually, the break-in lasts during the combustion of 4-5 liters of fuel
  2. 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
  3. 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.
  4. If the mower has not been used for a long time. The reason for the need for adjustment may be a winter break
  5. When fuel consumption increases
  6. If black carbon is found on the spark plug electrodes
  7. In the absence of gasoline entering the cylinder or poor engine start
  8. If a large amount of exhaust gas is detected
  9. Unstable engine operation, as well as difficult starting and sluggish set of revolutions

As you can see, lawn mowers have enough reasons to adjust the carburetor. 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.

Adjusting the carburetor on lawn mowers 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 be carried out step by step in compliance with the recommendations. Before starting work, it is necessary to carry out preparatory actions, namely:

  • Flushing the engine is desirable, but not necessary
  • 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 a malfunctioning candle
  • Check if 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 only slightly
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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 move, 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. To begin with, 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:

  1. Regulator marked L with it you need to start tuning manipulations. 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 in so as to reach the maximum value. Usually this bolt rotates until it stops and then looses ¼ turnover. If dips are found, it is necessary to tighten the bolt again until it stops, and loosen it by 1/8
  2. The screw marked T or LA 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. The mixture becomes leaner and power or thrust is lost. Reduced speed at XX indicates 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
  3. The screw marked H, this screw is responsible for adjusting the combustible mixture at high speeds. It is with this screw that adjustment 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:

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

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 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.