Stihl Trimmer Adjustment

Carburetor for trimmer: device, do-it-yourself tuning When do you need to adjust the carburetor of a household trimmer? Carburetor device benzos, do it yourself carburetor adjustment

When is the carburetor setting of the household trimmer required?

Adjust the built-in trimmer carburetor when:

  • Running in a new engine, during which 4 to 5 liters of fuel mixture were used;
  • Sudden changes in weather;
  • Changing the air vacuum, for example, when the brushcutter is often used in mountainous areas;
  • Long-term simple trimmer;
  • Intensive growth of loads on the power unit of brushcutters;
  • Arbitrary unscrewing of the built-in carburetor adjusting screws, 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 a standard trimmer spark plug;
  • Starting the engine and its arbitrary shutdown or slow set of revolutions;
  • Lack of fuel flow into the cylinder of the power unit;
  • An increase in the volume of emitted waste gases.
Stihl Trimmer Adjustment

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

Carburetor device gas cutters

The standard design of any gasoline 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 practically the same for all brushcutters, regardless of their design features and purpose.

The brushcutter carburetor consists of an all-metal aluminum housing 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 the 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 air is sucked in. This is due to the fact that in the zone of the smallest diameter the level of air vacuum 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 carburetor device of the brushcutter includes a throttle valve, the main task of which is to regulate the volumes of intake air. The larger the amount of air, the higher the rated power of the trimmer power unit. Another function of the damper is to facilitate cold starting of the engine. If the brushcutter starts up for the first time after a long period of inactivity, the shutter must be closed. Immediately after starting the motor, the part must be opened, otherwise the internal combustion engine will stall.

The carburetor for the trimmer 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 cylinder of the motor 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.

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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 flows through the integrated inlet and outlet valves, then through the strainer and fuel pipe. The fuel then flows near the needle and gradually fills the chamber equipped with the control diaphragm.

The standard carburetor trim valve is connected to the diaphragm with a lever. Below the built-in membrane is a cavity into which air is sucked in through a special opening.

The carburetor for petrol cutters 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.

Carburetor for trimmer: device, do it yourself setting

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

Do-it-yourself carburetor adjustment

Periodic adjustment of the trimmer carburetor should be performed on a serviced and fully serviceable 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 brushcutter engine must operate under a certain load. It is best to install a cord of the appropriate diameter or cutting knives on the trimmer.

After installing the cutting elements, the operator should start the engine of the trimmer and leave it to work 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:

  1. The L regulator, located on the right, is responsible for enriching the fuel mixture with air when the engine is running at low speeds. 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 alternately to the right or left. Once the maximum speed is reached, the screw will need to be turned 1/2 turn to the left;
  2. The T or LA screw 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, accordingly, it will increase;
  3. The regulator H, provided on the left, is responsible for enriching the fuel mixture with air when the internal combustion engine trimmer is running 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. Then screw H will need to be turned 1/2 turn to the left.
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Performing these steps one by one will allow you to correctly adjust the fuel trimmer assembly, without the risk of exceeding the permissible load on its main working mechanisms.

Fuel ratio

I read somewhere that if different proportions of preparation of the fuel mixture are indicated in the manual for the petrol cutter and on the oil canister, the proportion indicated in the manual should be used.

For a long time, it did so from the engine to the gas tank, excess oil flowed down and carbon deposits constantly formed on the candle, since the manual indicated the proportion for the run-in engine 1:25, and on the canister 1:50. After switching to a 1:50 ratio, the appearance of oil drips stopped. The plug continued to burn, but with less intensity (the carburetor was not yet adjusted).

Until now, some users of gasoline tools determine the proportion of the fuel mixture by eye. If during the preparation of the mixture the amount of oil is underestimated, after a while an extraneous sound may appear immediately after starting the engine, gradually disappearing during warming up, and the engine stops with a sharp jerk. Continued use of the trimmer in this mode will lead to its failure.

Gas cutter or trimmer

A trimmer is a broader concept than a brushcutter (brushcutter), since it can also be electric. A petrol trimmer and a petrol cutter are one and the same.

Some authors claim that the trimmer is a weaker tool in contrast to the more powerful petrol cutter, which can be used for cutting bushes. Personally, I have a tool with a maximum power of 1.7 kW and is capable, as stated in the instructions, to mow small bushes up to 10 mm thick. The user manual is called Petrol Trimmer.

Adjustment of the carburetor, trimmers, trimmers

Increased fuel consumption and the rapid formation of carbon deposits on the brushcutter candle when using a properly prepared fuel mixture indicate the need to adjust the carburetor. Here’s how to tune trims with carburettors that have a single fuel adjusting screw.

Carburetor adjustment

Flush the air filter before adjusting the carburetor. It is recommended to rinse it after every 10 hours of operation. After that, you can start adjusting. The graph shows an example of a PRORAB-8406 petrol trimmer carburetor. The numbers indicate the adjusting screws that we will use.

PRORAB-8406 petrol trimmer carburetor adjusting screws

Purpose of adjusting screws:

  1. Fuel mixture adjustment screw.
  2. Idling adjustment screw.
  3. Maximum speed limiting screw.

Start a petrol cutter and wait until it warms up.

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 confidently 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 rotating. If the engine starts poorly, increase the idle speed even more.

Maximum speed limitation

After adjusting the fuel mixture and low speed, check how the petrol cutter engine will operate 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 the maximum speed or turn it out 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.

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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 petrol mowers. Vibration can cause the adjusting screws themselves to turn.

The main problems and malfunctions of the carburetor.

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

  1. Blockage.
  2. Breaking.

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 strainer, 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).

The carburetor starter in most cases does not function due to blockages. Use acetone or the same gasoline for flushing.

Blowing compressed air into carburetor parts is an acceptable and convenient repair practice.

Carburetor device gas cutters

The base of the carburetor is an aluminum case. 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 an air stream.

Outside the carburetor is installed:

  • Fuel pump;
  • Jet system;
  • Fuel-air mixture control system;

Do-it-yourself carburetor adjustment for petrol cutters

Petrolcutters, like all petrol powered tools for the garden, are not difficult to maintain. It is possible and necessary to repair, configure yourself. For example, adjusting the carburetor of a petrol cutter with your own hands is a matter of five minutes.

The carburetor from the petrol cutter is a unit in the power system. In it, like any carburetor, there is a process of mixing air and fuel (gasoline) for further supply to the engine cylinders.

The principle of operation of the carburetor petrol cutters

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 union in the carburetor. The fluid then flows through the pump inlet and outlet valves. Filtered by the grid. It moves through the needle valve into the membrane chamber.

Phased operation of the device:

  1. Air supply to a tube with an air baffle (damper). The baffle regulates the intensity of the air flow.
  2. The fuel supply system is necessarily narrowed by a diffuser to increase the flow rate.
  3. 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 flows through the jet.
  4. 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.
  5. The air / fuel mixture enters the engine cylinder through the fuel pipe.