How to Adjust a Gas Cutter Carburetor?

A brushcutter or trimmer, despite its relative simplicity (compared to a car engine), sooner or later fails. There comes a time when a long downtime and restarting the gasoline unit is not enough. you need maintenance. In advanced cases, repair is required, more precisely, the replacement of worn parts with the same new ones. Until you are faced with the need to replace your used parts, carburetor maintenance is required. cleaning, washing, reconfiguring mechanisms.

Carburetor device

Benzokosa (Lawn Mower) contains a base. a housing made of aluminum, which houses the rest of the parts, working seamlessly 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 with the air. the oxidizing agent, in which the fuel burns (gasoline-oil mixture).

Channels branching from the diffuser stroke deliver fuel, with which injected air is mixed, which carries away gasoline vapors. Outside the main carburetor compartment:

  • jets;
  • mini fuel pump;
  • a unit that regulates the mixing of fuel with air.

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

Principle of operation

Fuel injection and filtering procedure In the engine, the brushcutters are as follows.

  1. Using the throttle, the amount of air supplied to the diffuser is set. The more air is supplied, the more oxygen gasoline needs for combustion, and the more power is released in the form of heat. Heat energy is then converted into mechanical energy.
  2. A diaphragm pump pumps the required amount of gasoline.
  3. Further, gasoline passes through the engine fitting.
  4. Fuel flows through the suction and exhaust valves.
  5. The fuel is filtered using a strainer.
  6. Through the needle valve, it also enters the chamber with the membrane.

The staged operation of the carburetor is as follows.

  1. Air enters the duct with an air damper. The damper sets the desired air flow rate.
  2. In the gas injection unit, the diffuser is narrowed. this is necessary to give a higher air flow rate.
  3. Fuel passes through the compartment with the float and passes the jet, falls into this narrowing of the tube. The float compartment doses gasoline. In this compartment, the pressure is in equilibrium. In a narrowed tube, it goes down. Due to the difference in both pressure values, gasoline also passes through the nozzle.
  4. The accelerated stream sprays gasoline, converting it into aerosol vapors. The resulting gasoline-air mixture is ready for ignition in the combustion chamber.
  5. After passing through the fuel pipe, this mixture is in the carburetor cylinder.
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Conclusion: in order 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 the oxygen in such a mixture is less than 10%, the fuel does not burn, therefore, the engine will not start or stall immediately.

In the case of buying a Chinese trimmer, it is worth considering that it differs little 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.

Major issues

Malfunctions of the carburetor of the brushcutter or trimmer, despite the relative simplicity of their elimination, sometimes require a long search by the exclusion method. The main reasons are as follows:

  • unsatisfactory quality of gasoline cleaning;
  • air filter clogging;
  • accumulation of deposits and carbon deposits in the compartments and strokes of the carburetor.

Each of the problems has its own reasons.

Fuel Blower Malfunction

The most repeated failure is wear, rupture of the membrane. As a result, her non-fit. Fuel strokes are not sealed at certain stages of the engine cycle. The reasons here are:

  • you work too long on a scythe or trimmer without a break;
  • low-quality fuel
  • exhaust gases enter the pulse channel.

Video: How to Adjust a Gas Cutter Carburetor?


A deformed membrane has several bad consequences:

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

As a result, the internal space of the fuel pump is polluted from the side of the pulse channel.

Strainer clogging

The causes of the clogged strainer are poor fuel cleaning, damage to the hose and / or discharge head.

Failure of the adjustment lever

The wear of the contact face of the lever is a consequence of an incompletely refined fuel, which includes grains of sand or particles of clay, metal or other inclusions insoluble in liquid hydrocarbons. There is a problem with fuel injection, the motor without load is functioning intermittently.

Inlet needle defective

The inlet needle breaks due to the presence of particles of metal and stone in gasoline. As a result, the seat of the inlet needle does not fit snugly against it; the fuel mixture flows. There is too much air in the combustible mixture created by the carburetor, which makes the motor “sneeze” during operation. Finally, the needle can stop due to poor-quality gasoline, or the unit has been idle for a long time.

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Clogging the adjustment space

Deposits may accumulate in the adjustment compartment. The needle does not completely cover the hole, and a lot of gasoline enters the fuel chamber. the engine overfills it, possibly it also fills the spark plugs. Because of this, the gasoline-air mixture contains an increased amount of gasoline vapor. Efficiency drops markedly.

Corrupted diaphragm adjustment

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

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

Intake control lever sticks

Jamming of the adjusting lever is a consequence of improper installation, accidental bending. The contacting face will find the wrong position. This will disrupt the additional injection of gasoline.

The damper has worn out

The throttle and air damper become unusable due to the ingress of dust, metal particles, etc. Damaged dampers are similar to sandblasted parts. Due to the wear of the dampers, the motor efficiency is reduced, breakdowns are detected. The 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 model of a scythe or trimmer. In the end, the motor shaft will suffer. its pieces fall into the engine channels, causing the piston to be broken.

Carburetor cannot be adjusted

The springs on the adjusting screws are to blame for the fact that the adjustment is too coarse (the parameters cannot be set exactly). The manufacturer of a brushcutter or trimmer can supply excessively thick and stiff springs. You can find others either in workshops where such equipment is repaired, or purchased from any dealer or official representative of the company that produced the motor for your trimmer or mechanical scythe.

The primer broke

Primer. a manual mini-pump for forced pumping of fuel into the carburetor. To successfully start the engine, you may need to pump 20 ml of gasoline manually.

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Elimination methods

List of upcoming work with the engine may be as follows:

  • fuel pump replacement;
  • disassembling and washing 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);
  • adjustment of inlet, outlet and needle valves;
  • replacement of dampers;
  • cleaning of fuel channels and diffuser;
  • replacement of screw springs;
  • primer change.

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.

Carburetor adjustment

Do-it-yourself diagnostics and adjustments to the carburetor can take just a few minutes.

Rinse the filters before starting it (see instructions). You can adjust the carburetor yourself with the help of three adjusting screws.

To do everything right, start the engine. Your actions are as follows.

  1. Find idle speed. To do this, unscrew the screw L to the right, and then to the left. Turning step. a quarter of a turn counterclockwise.
  2. Using the T screw, you can adjust the idle speed of the motor: increase when turning the screw clockwise, decrease. vice versa. The adjusted engine confidently works without load and without warming up. Heated. does not overstate.
  3. If you do not adjust the scythe, but the trimmer, then the rotations of the T screw set a larger margin in rpm. For both types of devices, stable rpm is set when the knife (or fishing line) selects the cutting height.
  4. The last turn the screw H. It sets the rate of supply of gasoline with air at close to maximum speed, engine power, engine warm-up temperature and fuel consumption.

To adjust the motor with screw H, proceed as follows.

  1. Open the throttle and squeeze the gas at maximum speed.
  2. Turn screw H clockwise until the engine speed is reduced.
  3. Slowly turn the same screw counterclockwise until the engine produces variable speeds.
  4. Turn the screw back a little (clockwise) until the motor runs smoothly. It is important to catch this line.

The result of fine adjustment is the complete combustion of the fuel and the white-brownish color of the spark plug. A gas-filled candle is much darker than a non-flood candle.

How to adjust the brushcutter carburetor, see below.