How To Adjust The Needle On The Trimmer Carburetor

How to adjust the carburetor of a gasoline lawn mower?

The adjustment principle is the same for almost all carburetor types.

Consider the example of the Husqvarna 128R trimmer.

There are three adjusting screws on the carburetor.

Which are designated by the letters L, H, T.

After that I let go of the throttle and set the engine idling with screw T. The engine should idle smoothly, stably and without Dergan. The trimmer head must not rotate.

If the engine smokes and (or) the engine is unstable at idle, then adjust the “mixture quality” with the screw L.

The adjustment procedure can be repeated if necessary.

First, let’s say that the carburetor of a gasoline lawn mower is adjusted in the following cases:

But many tweak the carburetor of their lawn mowers to make sure the engine is working properly.

Before starting the adjustment, you first need to perform trimmer maintenance (the trimmer and engine should be washed, the spark plug should also be replaced and minor defects removed). Do not forget to wash the foam element of the air filter (it is better to do this in warm water and soap, and then dry it properly).

So, now let’s move on, in fact, to adjust the carburetor:

There are only three adjusting screws for adjusting the carburetor lawn mowers: right (L), left (H) and lower (T).

1). Right screw (screw L). Adjusts the enrichment of the mixture at low speeds (this screw is adjusted first):

First, we find the maximum idle speed, by. Slowly turning the right screw to the right and left. Then you need to return this screw a quarter (¼) turn counterclockwise.

2). Bottom screw (T screw). Provides engine idle speed control. If it is returned clockwise, then the idle speed increases, if it is counterclockwise, then it decreases.

Correct adjustment is considered when:

3). Finally, the left screw (screw H). It regulates the enrichment of the high-speed mixture (it is regulated last).

The left screw adjusts maximum rpm, engine power, temperature and fuel consumption.

This, in fact, is the end of the adjustment.

Only specialists from specialized workshops can correctly adjust the carburetor of gasoline lawn mowers.

But there are times when you need to adjust it yourself. Usually this is when high idle speed or even the trimmer stalls when the speed decreases.

There are two adjusting screws on the carburetor Trimmer body.

One is designed to regulate the fuel supply, and the second. For idle adjustment.

If the cutting element of the lawn mowers rotates, it means that the idle screw must be turned counterclockwise until the spool stops turning.

If you need to increase the number of idle turns. The screw must be returned clockwise.

But I would NOT advise you to regulate the quality of the mixture with special screws.

I tried it myself, so the lawn mower stopped starting. And what I just didn’t do. I had to go to the workshop, where everything was returned to me to factory settings, or even better. Now I DO NOT stick my nose to the adjusting screw and I do not advise others.

In principle, the carburetor adjustment of a gasoline lawn mower is the same on most products. Here you can see how the carburetor is adjusted on different lawn mowers.

The universal instruction is as follows:

  • The main concept is that there are only three adjusting screws on the carburetor and each has its own designation: L, H, T.
  • Before starting the adjustment, fill in gasoline and only after that plant them with a scythe at full power.
  • Now we need an adjustment lever H, on which the screw sets 8500 revolutions, so as not to make a mistake, then you can use a tachometer.
  • We put the engine at idle, using T.
  • If there is smoke, then L will help to adjust the quality of the mixture.

Any carburetor has three types of adjustment. This is the maximum fuel supply (that is, the maximum valve stroke, which allows you to set the maximum speed), the screw for adjusting the amount of air supplied to obtain the fuel-air mixture, and the idle speed. For these adjustments, any classic carburetor is configured. Perhaps on imported hair, it does not have an adjustment for the amount of air supply. Usually, adjustment is not required throughout the entire life of the streamer.

The main purpose of the carburetor in lawn mowers. Mix fuel and air to start the engine. If the engine freezes during idle, or, being idle, the blades are still in motion, then it is necessary to adjust the idle screw on the carburetor.

This can be done as follows:

  • Set to “Off” / “Off” switch on top of the handle. Place the mower on a flat, level surface and let it cool completely.
  • Wear safety glasses and gloves.
  • Start the mower and let the engine idle a little. If the engine stalls, insert a small flat head screwdriver into the idle adjusting screw on the right front of the engine and turn it clockwise.
  • Restart the lawn mower. If the knives move in the same way as when idling, turn the idle adjusting screw counterclockwise until adjust to the desired state.

Chainsaw air filter

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

  • The engine warms up, that is, it starts about 10 minutes before the repair, and turns off when you start work (see How to start a chainsaw).
  • The air filter is checked and washed.
  • The chain is stopped by turning the screw T as far as it will go (see Chain oil).

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

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Adjusting the carburetor for lawn mowers

Before proceeding with the adjustment, you need to clean the filters very thoroughly. This work must be carried out in accordance with the annotation from the manufacturer. Further work with the carburetor is done by adjusting the three screws.

  • Right screw. Adjusting the air-fuel mixture. Turning the screw to the right and left is performed at idle speed. It is necessary to determine the maximum speed.
  • Left screw. Adjusting the air-fuel mixture. The work is performed at high speeds. The screw is adjusted last, the engine power and gasoline consumption will depend on its correct setting.
  • Bottom screw. Adjustment of engine operation. The work is done at idle speed. Clockwise rotation indicates increase, counterclockwise. Decrease.

Setting instructions

Carburetor adjustment is divided into two main steps. The first is called basic. How to adjust the carburetor on lawn mowers. Carburetor adjustment at full speed. How to adjust the carburetor by looking at the spark plug:. It is produced when the engine is turned on. The second is performed when the engine is WARM.

To carry out the procedure for setting up the carburetor successfully, you need to read the operating instructions for a particular model in advance to identify additional features of setting up the device.

Functions and working principle

In order to understand how the lawn mowers carburetor works, you should get acquainted with its operating principles. The main elements of the carburetor are the throttle valve, the function of which is to control the air supply. The operation of a device such as a carburetor can be considered in stages.

  • Air mixture supply to the compartment where the throttle valve is located.
  • Moving air flow assists in moving and atomizing fuel through the jet.
  • The resulting mixture (air fuel) is fed into the engine cylinder.

Having become acquainted with these main stages, we can conclude: the more the throttle valve is open, the more gasoline consumption during the mowing process.

What you need to have to set up

Every carburetor owner must have the right tools to adjust this system. There are three adjusting screws, which are located on the body of the device. They have their own markings:

  • L. Screw for low speed correction.
  • H. High speed adjustment screw.
  • T. Carries out regulation of idling, in most cases it is used for experiments.

Lawn mowers carburetor device

How To Adjust The Needle On The Trimmer Carburetor

The basis of the carburetor is lawn mowers. Aluminium case. It contains a diffuser (hole with internal contours). Air is blown through this hole. Here is the cross-section (orifice) of the diffuser depends on the oxygen (air) flow rate.

The diffuser is equipped with fuel channels. Fuel is drawn in from them using the air flow.

Outside the carburetor is installed:

  • Fuel pump;
  • Jet system;
  • Air-fuel mixture control system;

Do-it-yourself lawn mowers carburetor adjustment

Lawn mowers, like all gas powered tools for the garden, are not difficult to maintain. It is possible and necessary to repair, configure yourself. For example, do-it-yourself lawn mowers carburetor adjustment. Case of five minutes.

Carburetor from lawn mowers. This is a node in the power system. In it, like any carburetors, there is a process of mixing air and fuel (gasoline) for further supply to the engine cylinders.

The main problems and malfunctions of the carburetor.

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

  • Blockage.
  • Breaking.

In order to find out the cause of the breakdown, the fuel filter cap is unscrewed to remove the mesh filter. If there is simply accumulated dirt on it, then flushing in gasoline or blowing will help.

If there is visible damage to the mesh filter, a new one must be installed. There may also be damage to the fuel supply pipe (during repair, they practice checking this element).

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

Blowing out parts of the carburetor with compressed air blockages. Acceptable and convenient repair practice.

The principle of operation of the carburetor lawn mowers

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 goes through the fitting into the carburetor. The fluid then flows through the pump inlet and outlet valves. Filtered by the grid. The needle valve moves into the diaphragm chamber.

Phased operation of the device:

  • Air supply to a tube with an air baffle (damper). The baffle regulates the air flow rate.
  • The fuel supply system is necessarily narrowed by a diffuser to increase the flow rate.
  • 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 penetrates through the jet.
  • 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.
  • The air / fuel mixture enters the engine cylinder through the fuel pipe.

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 for lawn mowers and trimmers, you need to understand the principle of their operation. How the carburetor works on lawn mowers is described step by step and accessible below.

  • The carburetor of lawn mowers begins with fuel supply through the channel, as shown in the diagram
  • 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
  • Fuel is supplied through valves 3 and 5. Valve 3 is inlet, through which fuel is supplied to the under-membrane space, and valve 5. Exhaust
  • Further, the fuel moves along the channel and, passing through the fine filter, reaches the needle valve 14
  • The needle valve is connected via a lever to the control diaphragm 18
  • The needle valve is actuated by acting on the diaphragm. When it is necessary to pump fuel in order 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
  • 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
  • The membrane acts through a lever on the needle valve, whereby the chamber is filled
  • After starting the engine, the choke opens, causing the engine to run on a lean mixture as fuel mixes with air
  • When the chamber is full, the fuel mixture is supplied (sucked in) through the idle and medium speed jets (when the engine is running)
  • At the same time, the throttle valve is displaced from the initial position by 10-15 degrees
  • 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 is ignited in the cylinder
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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 scuffing 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 ​​\ u200b \ u200bthe design of a membrane carburetor 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.

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

A lawn mower or 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 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 lawn mowers or lawn mowers? 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 will not miss the moment of the need to adjust the carburetor, you should adhere to the following recommendations in the need for adjusting measures:

  • After the engine has run in. Usually, the break-in lasts by burning 4-5 liters of fuel
  • When the fuel mixture of the second composition is poured into the tank, that is, the type of oil (even its color) and the brand of gasoline change
  • 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
  • If the mower has NOT been used for a long time. The reason for the need for adjustment may be a winter break
  • When fuel consumption increases
  • If black carbon is found on the spark plug electrode
  • In the absence of gasoline entering the cylinder or poor engine start
  • If a large amount of exhaust gas is detected
  • Unstable operation of the engine, as well as its difficult start and “Sluggish” set of revolutions

As you can see, lawn mowers have enough reasons to adjust the carburetor. Usually, masters who work with the tool for a long time detect changes in engine operation 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.

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 the automotive 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:

  • Diffuser or Venturi nozzle. Air is sucked into the system through this nozzle.
  • Air damper. Opens and closes the filtered air supply
  • Fuel channel of maximum speed
  • Fuel channels (jets) of idle speed XX and medium speed
  • Throttle valve. The opening amount is adjusted by pressing the gas
  • Impulse channel connection. Connects to the inner bore of the engine crankcase
  • Fuel inlet (union) (2). Provides fuel supply from the gas tank
  • Membrane (4). Responsible for sucking fuel from the gas tank
  • Fuel suction valve (3)
  • The valve for supplying fuel to the carburetor channel (5)
  • Filter element (6) or fine fuel filter
  • Fuel pipe (10)
  • Needle valve needle (14). Responsible for supplying fuel to the control membrane chamber
  • Camera. Fuel mixture that is fed through the jets and throttle valve to the cylinder
  • Control diaphragm (18). Provides manual fuel suction with primer
  • Diaphragm Lever (17)
  • Idle speed screw (15)
  • The screw for adjusting the amount of fuel supplied to the diffuser (13)
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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.

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, it should be performed step by step in compliance with the recommendations. Before starting work, it is necessary to carry out preparatory actions, namely:

  • Flush the engine. Desirable but not required
  • 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 whether 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 or primer leaks. 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 use.
  • Attach the spool or cutting knives to the tool spindle. Adjustment is carried out under load, even if only slightly

When all the preparation points are completed, we proceed to the direct process of setting up the carburetor. First, start the engine, and let it run for 5-10 minutes, depending on the ambient temperature. When starting the motor on XX, the spool or knives on the trimmer should NOT rotate. If they are moving, 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, identifying 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 we will consider the process of tuning the carburetor, which has three tuning screws:

  • Regulator marked L. From it you need to start tuning manipulations. It is necessary to rotate the screw when the motor is running. This screw is responsible for enriching the mixture at low speeds, so it should be screwed up so that it reaches its maximum value. Typically, this bolt rotates until it stops and then looses turn. If dips are found, it is necessary to re-tighten the bolt until it stops, and loosen it by 1/8
  • Screw marked T or LA. It 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 RPM 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 spool with the line or the steel cutting disc does NOT rotate. The rotation of the cutting elements contributes to the rapid wear of the clutch
  • A screw marked H. This screw is responsible for adjusting the fuel 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 a 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:

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

If the adjustment work is done correctly, the tool will work stably, the cutting element will not rotate at idle, 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. Typically, 2 screws are equipped with Chinese gas powered tools, as well as household units.

Summing up, it should be noted that one cannot help but understand the principle of operation of the membrane carburetor for lawn mowers and trimmers. It is important to have a screwdriver and a tachometer for adjustment. However, in order not just to adjust, but also the concepts of what you are doing, it is imperative to know the design and principle of operation.