How To Set Up A Carburetor On A Stihl Trimmer

Assembling the carburetor

Assembling the carburetor for lawn mowers is a snap. It is necessary to perform all actions in reverse order:

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 “quality of the mixture” 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 running as it should.

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 bottom (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, quietly turning the right screw to the right and left. Then you need to return this screw a quarter (¼) turn counterclockwise.

2). Bottom Screw (Screw T). Adjusts the engine idle speed. If it is returned clockwise, then the idle speed increases, if it is counter-clockwise, then it decreases.

Correct adjustment is considered when:

3). And, finally, the left screw (screw H). it regulates the enrichment of the high-speed mixture (it is adjusted 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 for regulating the fuel supply, and the other is for adjusting the idle speed.

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

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 mowers.

The universal instruction is as follows:

  • The main thing 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 be mistaken, then you can use a tachometer.
  • Set the engine to 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 is to mix fuel and air in order to start the engine. If the engine freezes during idle, or, while idling, the blades are still in motion, then it is necessary to adjust the idle screw on the carburetor.

This can be done as follows:

  • We set to the “Off” / “Off” position the switch on the 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 adjustment 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 speed adjusting screw counterclockwise until adjust to the desired state.

The main stage

The engine starts at medium speed and warms up for about 10 minutes. The screw responsible for adjusting the idle speed must move clockwise. This is how it looks in the diagram: how to adjust the carburetor on a chainsaw. It is released only when the engine comes into stable operation. It is necessary to check that the chain does NOT move during this process.

Step 20

Install the main membrane.

Step-by-step instructions for repairing a lawn mower carburetor. Final check at idle speed

Before this procedure, it is necessary to make a full adjustment of the components of the carburetor when operating at maximum speed. Next, you should check the functioning of the device in idle cold mode. How to clean a muffler on a 128 g Husqvarna trimmer, very often the problem of power loss lies on the surface and people, not knowing it, are trying to change the carburetor on a Husqvarna be. When the correct parameters are achieved during the adjustment, you will notice that the carburetor design exactly matches the following criteria:

Step 10

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

Step # 2

Remove the pump cover.

Step 11

Another particle of dirt can build up under the needle. See photo. This will also cause lawn mowers to fail.

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

Carburetor adjustment of Chinese lawn mowers / lawn mowers / trimmer / chainsaw. Set up in 5 MINUTES

Fuel supply adjustment at minimum speed

Before starting carburetor trimming Trimmer, it is required to warm up the engine to operating temperature.

Fuel adjusting screws

To do this, we start the internal combustion engine and let it run for 10-15 minutes at idle. At the first stage, when the trimmer is working, slowly tighten the screw “L” until the beginning of intermittent operation or until it stalls. Next, we unscrew the screw орота of a turn and check the speed of a set of maximum revolutions. If the lawn mower reaches high revs easily and quickly, this will be the most economical mode. In most of the models on the market, the fuel screw “L” is turned clockwise, but there are trim tabs where the decrease and increase in the supply of the mixture occurs in the opposite order.

DIY lawn mowers carburetor adjustment

Module adjustment does not apply to repair and replacement of spare parts is NOT required. In this case, the Lawn Mowers Carburetor Repair Kits are NOT needed.

Three screws are provided for debugging:

  • L. is regulated first, since it is responsible for supplying fuel at low speeds;
  • H. he is responsible for the supply of gasoline at high speeds, as well as for fuel consumption and temperature;
  • T. it is used to debug idle.

There are options, as a rule, this is the carburetor of a Chinese lawn mower, when only one screw remains on the body for debugging. for adjusting the idle speed. This does not mean that the module is configured automatically. it means that it will be difficult to carry out even such a type of repair as debugging. In the photo. adjusting the carburetor of a Chinese lawn mower.

  • The module is configured only when the engine is warmed up: for this, the device is pre-switched on for 10 minutes. If the mowing head rotates while idling, then the debugging is started immediately: turn the screw T counterclockwise until the rotation does NOT stop.
  • Adjustment begins with screw L. The screw turns to the right and left until it finds such a position in which the idle speed does not become maximum.
  • Then the screw is turned 1/4 turn counterclockwise. This will be his working position.
  • Idling must be adjusted by turning counterclockwise to increase the numbers of revolutions and clockwise to decrease. Its debugging consists in achieving such a mode in which a sufficient number of revolutions are made at the beginning of the rotation of the mowing head. In this case, the engine must work stably at different positions.
  • The position of screw L is determined last. at maximum speed, the trimmer should NOT work for more than 10 seconds. The throttle opens, the screw turns clockwise, very slowly, until a decrease in the number of revolutions is audible.
  • Then, also slowly, the screw rotates counterclockwise until the motor starts to malfunction. Then the screw is turned back clockwise until the engine again does NOT start normally.

If there is a tanometer, and if the recommended rpm values ​​are indicated in the product passport, the correction can be carried out more accurate, focusing not on hearing, but on the readings of the device.

Carburetor adjustment of lawn mowers by ear.

7 comments on the post “Adjustment and repair of the carburetor lawn mowers”

    Dmitry Pavlovich 07/04/2016

Please clarify. In the adjustment section, item 5, screw L. error? Should you read screw A? Thank you.

Prompt the initial position of the screws H L LA


Prompt the initial position of the screws H L LA

Thank you very much for the accelerator and did not know, but the defect is very important and creates a huge problem in which almost everyone is silent. BRAVO.

Maybe all the same tachometer is a rpm meter, and not a tonometer blood pressure meter

And I have L, H, LA, it’s LA instead of T?

The heart of any chainsaw is a two-stroke internal combustion engine.

The trimmer is not a complex household appliance, so most of its floor.

The need arose to acquire a reliable and loyal mechanical mind.

Gone are the days of the Soviet agro-industrial gigantomania. Disappeared gig.

Tiller is an economical tractor option for small-volume jobs.

In order to make such a nozzle as harrows, with your own hands, in addition to ph.

Adjusting the idle trimmer

Location of carburetor adjustment screws

How To Set Up A Carburetor On A Stihl Trimmer

The screw “T” (“AT”) serves as a limiter for the reciprocating movement of the fuel flap and when it is tightened, the engine speed increases, and loosening leads to a decrease in the crankshaft speed. Professionals advise adjusting the idle screw of lawn mowers so that the internal combustion engine works a little accelerated at minimum speed, but the head with a fishing line or knife remains motionless. If after the performed manipulations it is difficult to start the trimmer “cold”, then just tighten the “T” screw a quarter of a turn and try to start the engine again.

Carburetor Adjustment Lawn Mowers Highlights

Despite the high productivity, mobility and simplicity in work, modern lawn mowers can hardly be attributed to complex devices. Over time, any mechanism is subject to wear and tear, and then parts and assemblies require special attention from the owner. One of these trimmer elements is the carburetor, designed to form the fuel mixture and feed it into the combustion chamber. Increased consumption with proper observance of the proportions of gasoline and oil or a drop in engine power indicate the need to adjust the carburetor of the gasoline trimmer.

Adjusting the maximum speed screw for lawn mowers

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.

Tuning at maximum speed

The engine is adjusted at high rpm to protect against overheating and to reduce hand fatigue when pressing the throttle button. If the internal combustion engine is unstable at maximum speed, then the screw “H” must be tightened slowly to ensure smooth and precise operation.

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

Fuel supply adjustment

Start slowly tightening the fuel mixture adjustment screw until the engine does NOT start to stall or until it stalls if you do not have time to catch the moment. After that, unscrew the screw a quarter of a turn if the engine has not stalled, or half a turn if it stalled. Start the stalled engine. Check by opening the throttle as the engine picks up speed. Continue to loosen screw a quarter of a turn until the engine does NOT accelerate steadily when bumping. This will be the moment of the most economical stable operation of the engine. In the PRORAB-8406 petrol trimmer, the adjusting screws are turned clockwise, unscrewed. against, for some other brands of lawn mowers it may be the other way around.

Liked ?

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, it is imperative to put a new one. There may also be damage to the fuel supply pipe (during repair, they practice checking this element).

Blowing out carburetor parts with compressed air blockages is an acceptable and convenient repair practice.

Lawn mowers carburetor device

The basis of the carburetor for lawn mowers is an aluminum body. 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;
  • Fuel-air mixture control system;

Do-it-yourself lawn mowers carburetor adjustment

A lawn mower carburetor is a unit 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 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 intensity of the air flow.
  • 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 pressure drop, 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.

Simply put, adjusting the carburetor for lawn mowers is the creation of an optimal fuel mixture due to the correct supply of air.

How to adjust the carburetor on lawn mowers

Before adjustment, you must thoroughly clean the filters according to the maintenance in the instructions.

Further adjustment of the carburetor of the lawn mowers with their own hands is carried out with adjusting screws. There are three of them:

  • Right;
  • Left;
  • Lower.

Right (L). adjusting the fuel mixture for low rpm.

You need to find the maximum idle speed. To do this, slowly unscrew the screw (L) to the right and left.

To adjust, turn the screw a quarter turn counterclockwise.

Lower (T). responsible for adjusting the engine at idle.

  • Clockwise. increase;
  • Counterclockwise. decrease.

For the correct adjustment of the idle speed, it is characteristic:

  • Stable operation of a cold engine;
  • NOT overspeed of a hot engine;
  • A large reserve of turns for the trimmer head;
  • Stable operation of the engine when changing position (sharp lifting or lowering of the knife).

Left (H). mixture adjustment at high rpm. (The screw is adjusted last).

The carburetor setting for lawn mowers with the last screw is done as follows:

  • Open the throttle to full, while at the same time give full throttle. Turn the screw clockwise until the revolutions fall (in this case, orientate by ear).
  • Return the screw as slowly as possible counterclockwise until the engine runs unevenly.
  • Then they will return quite a bit, barely Hearing stable, even work.
  • For a more visual use of skills, it is more convenient to consider the work of an experienced user:

Interestingly, from the point of view of the author. The setting (its correctness) is determined by the color of the plug, and not only by the speed and stability of the engine.

Correct adjustment of the carburetor with your own hands in this case. combustion of the fuel mixture without residue, the color of the candle should be light brown.