Adjusting the grass trimmer carburetor with your own hands

Carburetor for grass trimmer: adjustment, adjustment with their own hands

Trimmers, in addition to electric motors, have gasoline internal combustion engines. This mechanism requires special attention, because if it is set incorrectly, it will either refuse to work, or will work with interruptions and loss of power. Basically, the adjustment of the engine is to adjust the fuel supply, and this is done with the help of the grass trimmer carburetor.

Grass trimmer carburetor

The carburetor for grass trimmer. one of the most important units of the unit, which is responsible for the fuel mixture. With improper handling of the technique, the element can be damaged, which makes it impossible to operate a brushcutter without repair. To repair a garden tool you need to know about its construction, how it works and how to adjust it.

design features and principle of lawnmower carburetor operation

Structurally, carburetors from well-known brands and Chinese manufacturers practically do not differ.

The design of the brushcutter carburetor consists of the following elements:

  • priming pump;
  • Atmospheric diaphragm tuning system;
  • The primer, which facilitates the start of the engine;
  • Cold stroke system;
  • Elastic two-valve plate;
  • Metered system with a rotating rotor;
  • Throttle valve.

The model functions as follows:

  • From the air damper, the air goes to a tube that increases or decreases its flow;
  • In the area with a hole for the fuel mixture is a narrowed zone. the diffuser. In this area, the air moves faster;
  • The fuel-air mixture flows from the float chamber through the nozzle into the carburettor tube. The float determines the amount of fuel;
  • Fuel is picked up and atomized by the increased air flow. Creates an air-fuel mixture with sufficient density;
  • It draws in the mixture from the cylinder through a pipe.

The concentration of air flow depends on how ajar the air damper is opened, respectively, more fuel is fed into the cylinder. Regulation of the brushcutter carburetor is to set the correct ratio of the flaps to achieve the optimum consistency of the fuel mixture.

Principle of operation of the carburettor

The brushcutter carburetor operates on the same principle at all times.

The function of the assembly is as follows:


  • First, a certain vacuum is created in the diffuser as a result of the intake stroke of the motor, which leads to the suction of air masses;
  • At the same time fuel flows through the nozzles from the combustion chamber and is then mixed with the air. After enrichment with air, gasoline begins to atomize gradually, resulting in an air-fuel mixture;
  • Then the ready mixture enters the cylinder of the internal combustion engine, where the piston acts on it. At the top of the stroke the fuel is ignited by a spark which is produced by the brushcutter’s spark plug;
  • Because the inner chamber under the diaphragm is connected to the ambient air by a channel, the valve opens when the diaphragm rises. This leads to the supply of air into the cavity under the diaphragm;
  • As soon as the chamber is filled with fuel mixture the diaphragm quickly returns to its original position. The valve closes as well.
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The scheme of operation of the node is repeated constantly, throughout the cycle of operation of the garden trimmer for grass.

How does the lawnmower carburetor work or the principle of operation?

Adjusting the carburetor of a Chinese lawn mower is completely identical to that of European, Russian, and manufacturers’ lawn mowers. To cope with the task of adjusting the carburetor on petrolmowers and petrol-trimmers, it is necessary to understand the principle of their functioning. How the carburetor on the gasoline mower works, step by step and accessible is described below.

  • The operation of the lawnmower carburetor begins with the fuel supply through the channel, as shown in the diagram
  • Fuel is sucked into the carburettor through a pulse channel connected to the engine crankcase. Due to air rarefaction, the flexible diaphragm number 4 in the diagram above moves
  • The fuel is actuated by valves 3 and 5. Valve 3 is the inlet valve through which fuel enters the space below the diaphragm and valve 5 is the outlet valve
  • Then the fuel moves along the channel and, passing the fine filter, it reaches the needle valve 14
  • The needle valve is connected to the pilot diaphragm 18 by means of a lever
  • 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 cap of the hand pump. On impact, the needle opens and the fuel mixture fills the chamber
  • When the engine is started (cold), the opening of the needle is due to the rarefaction with the air damper closed. This vacuum acts on the diaphragm 18 through the idle and high speed nozzles
  • The diaphragm acts on the needle valve through the lever and the chamber is filled
  • After the engine is started, the air valve opens and the engine runs on a lean mixture as fuel is mixed with the air
  • Fuel mixture with full chamber is fed (sucked) through nozzles at idle and medium speed (when the engine is started)
  • The throttle valve moves from its original position by 10-15 degrees
  • When the work is done under load, the fuel begins to flow into the chamber through the high rpm nozzle, and the throttle turns an angle of up to 90 degrees (depending on the force of the pressure on the gas). In all operating modes, the choke must be open so that fuel and air can mix and ignite the mixture in the cylinder

The working principle of the lawnmower carburettor is illustrated below. Based on the diagram, you can not only understand the principle of operation, but also to identify breakdowns and other malfunctions of the mechanism.

When operating the tool, it is necessary to take into account the presence of one more nozzle. The nozzle is located between the no-load and full power ports. It is needed to eliminate the strong depletion of the mixture, which occurs in the case of the motor under-load. Such a situation does not exclude the possibility of scoring of the pair. Fuel is sucked into the chamber through an additional channel (nozzle), thus enriching the fuel-air mixture. The diagram below shows an additional jammer, which is marked with the number 1.

Having an idea about the design of the membrane carburetor of brushcutter and the principle of operation, it will not be difficult to make its adjustment with their own hands. Adjusting the lawnmower’s carburetor requires the use of adjustment screws. The diagram above shows two adjustment screws, but most modern gasoline trimmers are equipped with three screws. Three tuning screws allow you to fine-tune the settings and have a stable and smooth performance of the engine.

adjusting, grass, trimmer, carburetor, your, hands

Adjusting the carburetor of the lawnmower of the German manufacturer

Using a lawn mower for landscaping work involves the presence of wear and tear, and sometimes breakage of its mechanisms. But since this tool can not be attributed to complex household appliances, all the failures are solely mechanical in nature, which can be corrected with your own hands. In a number of cases, it is enough to carry out adjustment work that returns the tool to normal working condition. One of such operations is the adjustment of the lawnmower carburetor in manual mode. The task of the carburetor is to mix air with fuel before feeding it into the engine. And if the proportions do not match, there will be visible failures in the work of the grass trimmer:

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How to set The High Air / Fuel Mixture on an Echo 2 Cycle Weedeater / Line Trimmer Carburetor

The whole process of adjusting the carburetor of the brushcutter brand involves only the adjustment of the position of the three screws: L. adjustment of gasoline supply in the mower at low rpm, H. adjustment of high rpm and fuel consumption, T. adjustment of idle speed. So, if you need to adjust the carburetor of a gasoline lawnmower line 55 or other types of this series, the following steps are performed:

  • Warm up the engine (10 minutes of idling is enough).
  • Adjust the H screw by turning to the left/right until the maximum idle speed.
  • From the point found, turn counterclockwise in ¼ turn, which will set the desired working position.
  • Idle speed adjustment of the gasoline mower carburetor is carried out similarly, by turning counterclockwise (decreasing revolutions) and clockwise (increasing revolutions). Achieves maximum motor stability in different positions.
  • Screw L is regulated the same way, with small rotations up to the maximum indicator.

The whole process is carried out by ear, so it is worth getting a tanometer for more successful work. Maximum tool maintenance can be performed by the masters of “Grasshopper Motors”, as well as buy oil for the compressor and buy all the necessary spare parts and components for timely maintenance.

Gasoline mower, as its name suggests, is equipped with internal combustion engine that uses gasoline as fuel. For it to burn inside, it requires air to form a reaction. The latter creates thermal energy, which is then converted into mechanical energy.

adjusting, grass, trimmer, carburetor, your, hands

To supply the fuel already with air in the cylinder of the motor and uses the carburetor.

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

The gasoline passes into the mixing chamber with air on top. The throttle blocks the fuel from entering the cylinder. When the mower pedal is depressed, it opens and the fuel flows in and the engine picks up speed. At most, the throttle plate can be turned up to a 90 degree angle, which depends on how hard the accelerator pedal is depressed. A vacuum is created in the mixing chamber and a strong stream of air mixes with the fuel and carries it into the cylinder.

At low RPMs, the idle system is used where the throttle is not fully opened, but partially.

The carburetor filter cleans dust and other small particles from the fuel and prevents them from harming the jets. If they are clogged, the engine output will be noticeably reduced.

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

When the carburetor needs to be adjusted?

Stable operation of the brushcutter carburetor largely depends on its proper adjustment.

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Adjustment of the assembly is required in the following cases:

  • After running-in the new trimmer for grass, when during the work was spent 4-5 full tanks of fuel;
  • due to the operator frequently changing the brand of gasoline used for refueling;
  • as a result of a sudden change in the weather;
  • due to long storage of the grass trimmer;
  • as a result of an accidental unscrewing of the trimmer‘s adjustment screws caused by the engine’s strong vibration;
  • Due to a sudden increase in the amount of fuel used.

Adjust the carburetor of the trimmer will also need to be adjusted in cases where the tool’s spark plug quickly becomes soiled, as well as a sharp increase in the volume of exhaust gases emitted by the trimmer.

Adjusting the lawn mower carburetor with your own hands

Regardless of the garden tool model, the adjustment of the grass trimmer carburetor requires careful preliminary preparation. The owner of a brushcutter will need to check the spark plug, the air filter and the carburetor itself. If there is dirt, all the elements need to be cleaned, or if necessary, replaced.

The grass trimmer comes standard with 3 adjustment bolts. The first one is marked with the letter L and is used for adjusting the engine when it runs at a low RPM. The second bolt is marked with the letter H, and is required for adjustment of the engine when it works at maximum speed. The third bolt can be marked with the letters T or LA. with his help, the operator can adjust the work of the engine at idle speed.

The process of adjusting the carburetor of a brushcutter looks as follows:

  • First you need to do a series of actions with the adjusting bolt L. For this purpose turn it clockwise until it stops. After that the bolt L must be turned half a turn in the opposite direction. This will give the opportunity to adjust the optimal oxygen enrichment of the fuel mixture during the work of the engine at low revolutions;
  • Then it is necessary to adjust the work of the engine in idling mode. To do this, turn the bolt T alternately in different directions until the mowing head or knife stops rotating;
  • At the end you need to adjust the level of oxygen enrichment of the fuel when the engine works at maximum rpm. This requires turning the bolt H clockwise as far as it will go and then back 1/2 turn in the opposite direction.


At the end, the operator must shut off the grass trimmer motor and start it up again. If the node was adjusted correctly, the brushcutter engine will steadily gain speed when the trigger is pulled and drop it quickly when the trigger is released.

How to adjust the weed trimmer on a brushcutter

Most modules have adjustment screws, and to understand their functionality is usually helped by a diagram:

adjusting, grass, trimmer, carburetor, your, hands
  • L. for fuel supply of low-speed mode;
  • H. fuel supply at high revolutions and its consumption;
  • T. adjustment of idle rpm.

Adjusting a brushcutter made in China can be difficult because there is only one screw that is responsible for the idle speed.

important! The answer to the question of how to adjust the carburetor mower Champion, it is better to look at the video, where it does a professional.

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