Stihl Trimmer Fuel Adjustment

Stihl Trimmer Fuel Adjustment

On trimmers, in addition to electric motors, gasoline internal combustion engines are installed. This mechanism requires special attention, because if configured incorrectly, it will either refuse to work or will work intermittently and loss of power. Basically, adjusting the engine is to adjust the fuel supply, and this is done using the trimmer carburetor.

The main problems and malfunctions of the carburetor

Strainer There are only two tasks with this element:

In order to find out the cause of the breakdown, the fuel filter cover is unscrewed to remove the strainer. If it just accumulated dirt, then washing with gasoline or blowing will help.

With visible damage to the strainer, it is imperative to install a new one. There may also be damage on the fuel supply pipe (during repair, check this element).

The carburetor starting device almost always does not work due to blockages. Use acetone or the same gasoline for flushing.

Blowing off carburetor parts with a blockage of compressed air is an acceptable and comfortable repair practice.

The throttle body, the bundles of carburetor parts, the intake or exhaust pipe. All of these parts are subject to depressurization. Probably you can check with a simple method. Smear the problem area with soap suds.

Tips for repairing a carb trimmer

  1. Regardless of the manufacturer, there is a factory defect of the carburetor parts of the lawn mowers.

Adjusting screw spring

For example, the adjustment method described above may not give positive results with an excessively large number of turns at the spring of the mixture feed screw and, as a result, the impossibility of optimally reducing the level of gasoline supplied. To eliminate this, you can independently shorten the spring yourself or purchase a new one in accordance with the instruction manual.

Many owners of lawn mowers when buying oil follow the recommendations indicated there for the preparation of the fuel mixture.

Oil for gas trimmer

So, often the information on mixing gasoline and oil indicated on the bank differs from the indications in the trimmer’s passport. As a result, black soot can quickly form on the spark plug, which leads to a drop in power and an increase in fuel consumption. Therefore, when preparing the working mixture, the recommendations specified in the instruction manual should be followed. In most cases, the proportion for a run-in ICE is 1:25. It is worth noting that many owners of the tool prefer to cook fuel “by eye”, which will inevitably lead to rapid wear of the piston spit in case of a reduced portion of oil and the formation of soot on the spark plug with an increased amount of lubricant.

The correct tips for setting up the trimmer carburetor correctly performed above will help to avoid not only engine overheating and increased fuel consumption, but also significantly increase the life of other parts and components of the tool. Pay attention to the operation of the lawn mowers in all modes and timely carry out regulated maintenance and repair of the tool.

The principle of the carburetor lawn mowers

The throttle valve determines the amount of air for supply, and engine power directly depends on this.

Fuel is sucked into the carburetor system by a pump (its membrane). Then it passes through the fitting in the carburetor. Further, the fluid moves through the inlet and outlet valves of the pump. Filtered by mesh. The needle valve moves into the membrane chamber.

Phased operation of the device:

  1. Air supply to the tube with an air baffle (damper). The partition controls the intensity of the air flow.
  2. The fuel supply system must be narrowed by a diffuser to increase the flow rate.
  3. Gasoline through the float chamber and nozzle tube with narrowing. A camera with a float adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with narrowing is already low. Due to the pressure drop, fuel enters through the nozzle.
  4. The acceleration of the air flow contributes to the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the necessary proportion or density is formed.
  5. The air-fuel mixture enters the engine cylinder through the fuel pipe.

The level of air density in the system depends on the area of ​​the open air damper. The wider the flap is open, the greater the fuel consumption and power.

Simply put, adjusting the carburetor on the lawn mower is creating the optimal fuel mixture due to the correct air supply.

About carburetor design

The carburetor is used to mix a combustible consistency with air, subject to well-established proportions. If clear doses are not respected, the health of the motor is at risk. When a huge amount of air enters during the mixing of the component, and there is not enough fuel, such a mixture is considered “poor.”

It should not be allowed and oversaturation, because with a large amount of fuel in comparison with air, malfunctions or deterioration of the motor are also likely. Adjustment of the carburetor is necessary not only before the initial implementation, but also when any differences in its work are revealed. Before working with a chainsaw, do not forget to run it in.

Carburetor parts

The carburetor design contains a standard set of parts, but may vary little depending on the manufacturer. Components:

  1. The basis. This is a special tube that visually resembles an aerodynamic design. Air passes through it. In the transverse direction, a shutter is located in the middle of the pipe. Her position can be changed. How to adjust the carburetor to How to change the piston on the trimmer. The more it is pushed into the passage, the less air enters the engine.
  2. Diffuser. This is the lent out part of the tube. Here’s what it looks like on how to adjust the carburetor on a chainsaw to set up. With its help, the air supply rate increases in the segment where the fuel comes from.
  3. Channels to supply fuel. The fuel mixture is contained in the float chamber, then passes into the nozzle, from which flows into the spray.
  4. Float chamber. It is a separate structural element that resembles the shape of a tank. Designed to constantly maintain an optimal level of fuel fluid before entering the channel from where air comes.

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Looking for cheaper models, but reliable and time-tested? Pay attention to Russian-made chainsaws.

Or explore overseas chainsaw manufacturers such as Stihl.

Trimmer carb setting

The initial step in restoring the correct operation of the fuel system is to clean the air filter.

Screw trimmer carburetor

Experts recommend rinsing it every 10-15 hours in a solution of water with detergents. Direct adjustment of the trimmer carburetor is carried out by three adjusting screws:

  • Fuel feed adjustment screw (“L”);
  • High speed adjustment screw (“H”);
  • The screw responsible for the engine idling (“T” or “AT”).

Adjusting the fuel supply at minimum speed

Before starting the carburetor adjustment of the gas trimmer, it is necessary to warm the engine to operating temperature.

Fuel Adjustment Screws

To do this, start the engine and at idle let him work 10-15 minutes. At the first stage, with the trimmer working, slowly tighten the screw “L” until the beginning of intermittent operation or until it dies. Next, unscrew the screw by ¼ turn and check the speed of maximum speed. If the lawn mower easily and quickly reaches high speeds, this will be the most economical mode. In most models on the market, the fuel screw “L” is screwed in clockwise, however, there are trim tabs where the decrease and increase in the mixture flow occurs in the reverse order.

Trimmer idle setting

Location of carburetor adjustment screws

The screw “T” (“AT”) serves as a limiter of the reciprocating movement of the fuel damper and when it is twisted, an increase in engine speed occurs, and unscrewing leads to a decrease in the speed of the crankshaft. Professionals advise adjusting the idle screw of the lawn mowers so that the ICE works a little faster at minimum speed, but the head with the fishing line or knife remains motionless. If it is difficult to start the trimmer “cold” after the manipulations, then it is enough to tighten the “T” screw a quarter of a turn and try to start the engine again.

Adjustment of the propeller

After restoring the fuel supply at minimum speed and adjusting the idle speed, it is necessary to check the stability of the mechanism at an increased speed.

Setting at maximum speed

Adjustment of the motor at high speeds is carried out in order to protect against overheating and reduce hand fatigue when pressing the accelerator key. If the internal combustion engine is unstable at maximum speed, then screw “H” must be slowly turned in to ensure smooth and clear operation.

During operation of the lawn mowers, it may be necessary to adjust the fuel feed screw (“L”) for an optimal set of revolutions.

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How to Adjust a Carburetor On a Carver Trimmer

DIY carburetor setup for chainsaw

For an independent carburetor option, it is necessary to familiarize yourself with its device and clarify the procedure for the work that is carried out to adjust the parts responsible for the proper functioning of the component parts of the device and parts close to it.

It is necessary to carefully handle objects for the system option, and also determine the compliance of the set characteristics with very acceptable values.

How to adjust

Before setting up the trimmer carburetor, do the following:

  • Flush the engine;
  • Replace or clean the spark plug;
  • Change to a new one or clean the air filter (it is recommended to wash it in warm, soapy water, squeeze it out and let it dry well).

It is also necessary to install a cord of a suitable diameter in the trimmer coil or install knives. This is done so that the engine has at least some load during the tuning process. After installing the cutting tool and starting the gasoline engine, let it warm up for 10 minutes.

If at idle of the engine you notice that the cutting tool rotates, then it is necessary to reduce the engine speed. This is done using the lower idle control, often marked with the letter “T”. The figure below shows the placement of the knobs on the Husqvarna trimmer.

But, for example, on a Stihl trimmer, this screw may be labeled “LA”.

So, turn the idle speed control to the left, until the trimmer head stops completely.

To adjust the carburetor, 3 regulators (screws) are used.

  1. The right knob L adjusts the level of enrichment of the combustible mixture at low speeds. It needs to be regulated first. Get maximum idle speed. This is done using the L knob, turning it left and right. After finding the point of maximum revolutions, return the regulator half a turn to the left (counterclockwise).
  2. The lower T (LA) knob is used to adjust the idle speed. By turning it to the left, the engine speed will begin to decrease, and when you turn the regulator to the right, the speed will increase.
  3. The left regulator H is responsible for the enrichment of the combustible mixture at high speeds. The enrichment setting completes the carburetor adjustment. Also, using this controller, you can adjust the maximum speed, fuel consumption and engine power.

Important! If the engine is allowed to run at full speed for more than 10 seconds, then it may fail.

To eliminate this trouble, adjustment will be required. With the engine running, give full throttle, then turn the “H” knob to the right until the reduction in speed begins. After that, the “H” knob must be slowly turned to the left until you hear the engine running unevenly. Then turn the “H” knob to the right until the engine runs smoothly.

After carrying out the above steps, the carburetor adjustment can be considered completed. After proper adjustment, the engine must confidently gain revolutions, slightly quadruple at maximum revolutions, and when idling, the cutting tool should not rotate. This manual is suitable for adjusting carburetors on the Huter, Patriot, and others.

There are also carburetors without a screw, which is responsible for the enrichment of the combustible mixture at low speeds. That is, they have only 2 adjusting screws: the idle speed regulator and the fuel mixture quality regulator at high speeds. You can learn how to tune this type of carburetor from this.

What you need to have to configure

Each carburetor owner must have the necessary tools to adjust this system. There are three adjusting screws that are located on the device. They have their own markings:

  • L. Screw for low speed correction.
  • H. Screw for adjusting high revs.
  • T. Regulates idling, in most cases it is used for experiments.

Chainsaw Air Filter

Before adjusting the carburetor, you need to prepare the device:

  1. The engine warms up, that is, it starts about 10 minutes before repair, and turns off when work starts (see how to start a chainsaw).
  2. The air filter is checked and flushed.
  3. The chain is stopped by turning the T screw all the way (see chain oil).

To carry out safe repairs, you need to prepare a flat surface where you can neatly position the device and unscrew the chain in the opposite direction. Need a tachometer. It determines the presence of a malfunction in the carburetor. When turning the screws, the sound should be perfect and absolutely even. If screeching notes are noticed, then the mixture is oversaturated.

First stage

The adjusting screws for the highest and lowest revolutions should be carried out clockwise until the highest resistance is encountered. When the screws reach the stop, you need to translate them in the opposite direction and leave when passing 1.5 turns.

Main stage

The engine starts at medium speed and it warms up like this for about 10 minutes. The idle adjustment screw should be clockwise. Here’s what it looks like in the diagram: how to adjust the carburetor on a chainsaw. It is released only when the engine comes into stable operation. It must be ensured that the chain does not move during this process.

Step-by-step instructions for repairing a carburetor lawn mowers

Carburetor Dismantling

A visual inspection of the carburetor will help to identify fuel leakage and air suction, but the main causes of device failure lie inside. Therefore, to determine and most importantly fix the breakdown, the carburetor must be disassembled.

To disassemble the carburetor lawn mowers a lot of effort is not necessary.

It is enough to unscrew the four screws on one side

And two on the other. This can be done using an ordinary Phillips screwdriver. Gently unscrew the screws and fold to the side. They may be needed during assembly. It is advisable to lay the table with a white cloth before disassembling, so that everything, even the smallest details that can fall out when disassembling, can be seen.

Step # 1

We begin dismantling from the side of the fuel supply system.

We remove the primer. The pumping bubble, which is noteworthy; it is simply impossible to install the carburetor parts incorrectly during assembly. Products have characteristic ebbs and holes.

Step 2

Remove the pump cover.

Step 3

Now remove the membrane. It is she who performs the function of pumping fuel into the carburetor.

During vibration, the membrane on the other side exerts pressure on the beam of the mechanism and the needle rises, which, in turn, opens the hole and fuel is supplied.

Step 4

Remove the carburetor cover with the injection mechanism.

Step 5

Next, another membrane is installed. We carefully remove it.

Step 6

Under the membrane is another gasket. We carefully clean it too, in no case damaging it.

Step 7

Next, go to the dismantling of parts on the back of the carburetor. As mentioned earlier, we unscrew the two bolts. This is an air supply system.

A valve is located here, which, when “gas” is added, opens and increases the flow of air into the engine.

After its removal, the bare body remains in the hands. Carburetor disassembled.

Identification of faults and their elimination

Now it is worth paying attention to the malfunctions that occur during the operation of the carburetor and methods for their elimination.

Problem 1: Clogged holes, channels and nozzles with dirt

The first thing that happens is that the holes and nozzles in the fuel supply system become clogged with dirt. Filters installed in the tank and directly in the carburetor do not help. They nevertheless pass small particles, which become the cause of the lawn mowing failure.

Step 8

Now we need to get the needle.

To do this, unscrew the bolt on the mechanism, holding it with your finger. The fact is, there is a spring there and careless action will cause it to be lost.

We take out the needle, see photo and spring.

Step 9

How to purge. The most effective way is the use of an ultrasonic bath.

It is filled either with a special liquid or with gasoline, a carburetor is placed there and under the influence of ultrasound, the so-called cavitation effect, the channels are cleaned of impurities.

The second option is cleaning compressed air.

You can use the compressor available on the farm and clean the carburetor channels. However, this method is effective if the pollution is not very large.

Step 10

Now we need to blow through the channels in the body and the carburetor cover. See photo.

Step 11

Another piece of dirt can get stuck under the needle. See photo. This will also lead to a failure of the lawn mowers.

Important! When cleaning the carburetor, never use needles, pins or wires. Even the slightest scratch will damage the carburetor. It will have to be changed entirely.

Problem 2: clogged fine filter

It is located on the carburetor cover and is a small metal mesh. Its pollution occurs very often. This is due to the deposition of oil, additives, and dirt on it.

Step 12

Sometimes, when disassembling into grids, a certain film is detected. For this carburetor, there is not enough fuel and the lawn mower either does not start, or it works intermittently. The cleaning methods are identical to the first reason: an ultrasonic bath, a compressor or a spray can with a special solution. In addition, if the mesh is thoroughly clogged, you need to take a soft brush for watercolor paints, dip it in gasoline and rinse it gently without damaging it.

Problem 3: membrane failure

Step 13

They have the ability to wear during operation. From prolonged use, they are deformed, stretched, lose elasticity, poor-quality fuel corrodes them, and can no longer perform their functions well. This also applies to the needle itself. The fact is that it is covered with a thin layer of rubber, which wears out during operation and can no longer fit tightly into the hole. Lawn mowing starts to work intermittently. To eliminate such a breakdown, all worn parts must be replaced. Where to get them?

It includes two membranes, a gasket, a needle valve and a spring.

All carburetor wearing parts can be replaced. Therefore, you should not rush and buy a new one, and you don’t need to run to the workshop either, repair is possible for any user of lawn mowers. Professionals claim that the quality of components in the repair kit even exceeds the characteristics of the carburetor’s native parts. Therefore, a well-repaired unit will work better than a new one.

Problem 4: wear of the bubble button for manual pumping

Step # 14

In addition, a bubble button for manual pumping of fuel may fail. The impact of gasoline on it leads to the fact that during prolonged use, the rubber corrodes and it begins to stick together or under the influence of low temperatures, for example, during storage, bursts. The button should also be replaced if necessary. In addition, her cost is small and will not affect the size of the repair budget.

Based on the foregoing, we can conclude that there are only three main malfunctions of the carburetor: clogging of channels, pollution of the fine filter and failure of components. In the first two cases, cleaning is enough, and in the third, the repair kit will help.

Carburetor assembly

Assembling a carburetor lawn mowers is not difficult. You must complete all the steps in the reverse order:

Step 15

Install a spring and a needle valve in the carburetor cover. Holding the spring with your finger, tighten the fastening bolt.

Step 16

Screw the valve of the air supply system to the body of the product with two screws.

Step 17

Turn the carburetor over and proceed with assembling the fuel system. First you need to put the gasket.

Step 18

Step 19

Fit the carburetor cover.

Step 20

Install the primary membrane.

Step 21

Fit pump cover.

Step 22

Install the plate with the manual fuel pump button and tighten the four screws.

The carburetor is assembled and ready for further use.

For the first time, repairing a carburetor for lawn mowers may seem like a complicated process, but if you have to disassemble it a second time, this procedure will not cause any particular difficulties.

If you did not find any of these problems in your carburetor, it is recommended to seek help from a specialized service.

Acceleration Test

If this does not happen or the speed increase is too slow, you must use the screw marked with the letter L. It turns counterclockwise. It is necessary to observe moderate movements, since the turn cannot be more than 1/8 of the full circle.

Maximum speed

If you make this figure more, the engine of the device will run to wear, which will lead to problems in the ignition system. When rotating this screw, the ignition processes of the device must be taken into account. If the slightest glitches appear, then the maximum speed value must be reduced.

Final idle check

Before this procedure, it is necessary to perform a full adjustment of the components of the carburetor when operating at maximum speed. Next, you should check the operation of the device in idle cold mode. How to clean a silencer on a Husqvarna trimmer 128 r, very often the problem of power loss lies on the surface and people without knowing it are trying to change the carburetor to Husqvarna be. When the correct parameters are reached during adjustment, you can see the exact compliance of the carburetor design with the following criteria:

  1. When the idle cold mode is connected, the circuit does not move.

Chainsaw Accelerator

  1. When even pressing the accelerator a little, the engine accelerates at an accelerated pace. With a gradual increase in pressure, you can notice that the engine speed is proportionally increasing, reaching the maximum allowable values.
  2. When the engine is running, you can compare its sound with a four-stroke device.

If violations are noted in the given parameters or the device was not fully adjusted, you need to perform the main setup step again. The story of how to adjust the carburetor chainsaw futlik There is a breather on this chainsaw. Sometimes actions are performed incorrectly. In this case, the device may fail due to the loss of the correct node settings. In this case, you will have to contact a specialist.

Dismantling the carburetor if necessary to check or repair the components

The device of different models of carburetors is almost the same, therefore, when working with them, you can use the standard scheme. All items must be removed carefully and then lay out in the order below, so that you can successfully arrange the objects in place at the end of the repair work.

Top cover removal

  1. The top cover is removed. To do this, unscrew the 3 bolts holding it in a circle.
  2. Foam is also removed, as it is the upper part of the filter that conducts air.
  3. The fuel hose is removed.
  4. The drive rod is displayed immediately on it.
  5. The cable tip is disconnected.
  6. The gas hose can be completely removed by steadily pulling it off the fitting.

To finally prepare the carburetor for a major overhaul or replacement of the smallest parts, you need to carefully disconnect it from the main system. Sometimes it requires further disassembly. Unscrew the components carefully and fold the fasteners in groups, as these small parts are easily lost.

Instruction for chinese

To correctly configure the carburetor of a Chinese chainsaw, you must first remember the factory settings of the device, then turn on the engine. In the future, you will have to leave it to work for several hours to accurately set your own parameters. Sometimes work is performed once after a ten-minute operation of the engine, but many Chinese-made models require special handling.

Chinese model of chainsaw

Adjustment Procedure:

  1. Events start at idle. Using the adjusting screws, you need to achieve a systematic set of revolutions by the engine, so you should first let it work at low speeds. A deviation from the norm is the movement of the chain along the bus. In this case, it is necessary to adjust the extreme position of the extreme screws so that the chain remains stationary.
  2. Switching to medium speed revs. Sometimes the engine smokes at the same time. This defect can be eliminated by tightening the screw to supply a leaner fuel mixture.

In this case, the smoke will disappear, but the engine speed will increase. It is necessary to adjust the settings to the level where, when you press the throttle, the engine gains speed, sharp jerks or interruptions are not heard.

  • Device engine check in progress. The chainsaw is transferred to the minimum speed, and then a rapid pressing of the lever is carried out. With maximum pressure, it is held for 3 seconds. If there is a malfunction in the engine, you need to gradually loosen the screw until the optimum position is reached.
  • Chainsaw should work for several hours in real conditions. It is necessary to engage in sawing wood, and then perform an inspection of all the elements involved in this event. If there are deviations, they need to be corrected using adjusting devices. When all defects have been eliminated and optimal settings have been set for the supply of correctly concentrated fuel, the process of setting up the device can be considered completed.
  • Look at the clearly:


    In order for the chainsaw to work properly, it is necessary to carefully carry out work on adjusting the carburetor in exact accordance with their priority. Here’s what it looks like on how to adjust the carburetor on How to adjust the needle. If there are any malfunctions in the operation of the device, you must independently perform its complete disassembly. How to adjust the carburetor Screw N set the speed as on different lawn mowers. In most cases, replacement of any parts that have become unusable is required.

    With a constant check of the quality of the carburetor settings and the implementation of timely actions to improve its operation, there are no problems with the chainsaw.

    About which chainsaw to choose. Read here.

    Husqvarna carburetor adjustment is done if:

    And, to be sure that the Husqvarna engine works as expected and that the maximum trimmer performance (lawn mowers, lawn mowers) is ensured.