How to adjust the carburetor on a gasoline trimmer. Trouble with the inlet adjusting lever

The device of the carburetor of the gasoline grass trimmer

Adjusting the carburetor of a brushcutter is a process that you need to master in order for the grass trimmer to work fully. The grass trimmer is a completely uncomplicated device that can only break in a few places and require mechanical repair or part replacement. Adjusting the device of the carburetor of a float-type brushcutter may require knowledge of certain subtleties. The nuances due to the model and the specifics of its operation will ensure a clear mode of mixing and feeding the fuel mixture.

Champion lawnmower carburetor, how to adjust? It is just a grass trimmer of the float type. a common option, designed to mix in the prescribed proportions of air and fuel. The main problems that arise during the operation of the motor are approximately similar to the malfunctions that overtake the carburetor in the car:

  • The engine may shut down as soon as it is started. The reason is that not enough gasoline is being supplied. This is called “poor” fuel;
  • Excessive gasoline leads to incomplete combustion, excessive mixture density and uneconomical consumption.

Carburetor repair

Important! You have to adjust the carburetor under different circumstances: change in temperature, octane number of fuel or type of oil, after winter or the end of the running-in period, load or spontaneous turning of the screws due to strong vibration of the housing. Some owners prefer to tune the module before each use to make sure it works correctly.

the spring may get in the way

My first attempt to adjust the lawnmower carburetor did not work because the fuel mixture adjustment screw spring interfered. The factory spring proved to be too thick in the compressed state and did not allow you to reduce the fuel supply to the necessary level. You had to pick up another spring and continue adjusting after replacing it.

Fuel mixture adjusting screw with spring

Pictured above is the factory spring, below is the adjustment screw with a matched spring. I am writing about it, because I am not sure that this is an isolated case, and someone else can face the same situation.

The main problems

Troubleshooting the carburetor of brushcutter or grass trimmer, despite the relative ease of their removal, sometimes require a long search by the method of elimination. The main causes are as follows:

Fuel blower malfunction

The most recurring problems are diaphragm wear and tear. As a consequence, its loose. The fuel passages are not sealed at certain stages of the engine cycle. The causes are as follows:

  • You have been working on your brushcutter or trimmer for too long without a break;
  • low quality fuel is refueled;
  • Exhaust gases enter the impulse line.

A deformed diaphragm involves several bad consequences:

  • Not enough gasoline or oxygen in the mixture;
  • engine starts after 10 or more unsuccessful attempts;
  • The engine knocks, clangs when running, etc. д.;
  • the working piston is deformed.

The inside of the fuel pump becomes contaminated on the impulse line side.

Clogged strainer

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

Control lever failure

Wear of the lever’s contact surface. the consequence of not completely clean fuel in which grains of sand or particles of clay, metal or other inclusions not soluble in liquid hydrocarbons have got. There is a problem with fuel injection, the engine does not run smoothly at no load.

Inlet needle is defective

Inlet needle is broken because of metal particles and stone in the gasoline. As a result, the inlet needle seat does not fit tightly, the fuel mixture leaks. Too much air in the mixture created by the carburetor and the engine may “sneeze” while running. Finally, the needle may stall because of bad gasoline or the machine has been idle for a long time.

Clogged adjustment space

Deposits can build up in the control compartment. the needle does not close the orifice completely and a lot of petrol gets into the fuel cell. the engine overflows and perhaps floods the spark plugs. The fuel-air mix contains an excessive amount of gasoline vapor because of that. The efficiency is noticeably reduced.

Adjustment membrane is defective

Diaphragm is often deformed (sometimes even ruptured) due to continuous operation of the brushcutter or grass trimmer for several hours. If you overdo this “shock” mode of operation, damage to the diaphragm is more likely. New breakdowns will pour from the horn of plenty:

adjust, carburetor, gasoline, trimmer, trouble, inlet
  • the piston will break;
  • the number of unsuccessful engine start attempts will increase dramatically;
  • the fuel mixture will contain too little gasoline;
  • Useful (thermal) power will drop sharply.

Inlet control lever is jammed

Control lever seizing up due to improperly installed or accidentally bent lever. The contacting edge will get in the wrong position. It will cause a disturbance in the auxiliary flow of gasoline.

Slide valve worn

Throttle and air dampers deteriorate from ingress of dust, metal particles, etc. into the air stream. д. Damaged flaps look like parts that have been blasted with sand. Flapper wear reduces engine efficiency and causes breakdowns. Piston and cylinder wear out.

Flaps fail due to improper maintenance of the air filter or failure of the air filter.

In some cases, this filter is simply not suitable for your model of brushcutter or grass trimmer. In the end, the motor shaft will suffer. its pieces get into the engine channels, causing the piston to be broken.

It is impossible to adjust the carburetor

The springs on the adjusting screws are to blame for the fact that the adjustment is too rough (you can’t exactly set the parameters). The brushcutter or weed trimmer manufacturer may have made the springs too thick and too stiff. Find others can either be found in shops where similar equipment is repaired, or purchased from any dealer or an official representative of the company that produced the motor for your grass trimmer or mechanical grass mower.

The primer is broken

Primer. a manual mini-pump for forcing fuel into the carburetor. You may need to pump 20 ml of gasoline manually to get your motor to start successfully.

Adjusting the grass trimmer carburetor with your own hands

Petrol-powered mowers, as well as all power tools for mowing grass, are not considered complex to maintain. They can and should be adjusted, repair with their own hands. So, for example, for five minutes of your spare time you can adjust the carburetor of a grass trimmer.

Often you need to adjust the gasoline supply to tune the engine, and this is done exactly by the carburetor of the gasoline mower. You have to pay very special attention to this kind of device. If used incorrectly, it may refuse to work or it will perform its functions with errors and high power consumption.

Today we will discuss the main causes of failure and step-by-step adjustment of the part with their own hands.

How the carburetor of a gasoline mower is arranged?

What is a carburetor? This is a complex part in the system of operation of a mechanical device. Every model mixes air with gasoline for future delivery to the working cylinders.

Important! The best and most recommended brands of brushcutters are Husqvarna, Hyundai, STIHL, Zama, Walbro.

At the heart of the lawnmower engine is an aluminum base, which has a diffuser (notch with internal restrictions). It is through this notch that the air flows are heated. The oxygen flow rate depends directly on the passage part of the diffuser.

To the diffuser the fuel paths adjoin. Through them the gasoline is drawn in by the air flow. And here on the outside of the engine are installed such parts:

Important! The density of the air in the carburetor depends on the volume of the opening of the choke. The more open the choke system, the more the unit consumes gasoline and the higher its power. That is, the adjustment of the carburetor on the trimmer is to create an optimal flow of fuel through the correct air supply.

When to adjust the carburetor in a trimmer?

This is the case when it is necessary to adjust the device:

  • A new engine used 5 liters of fuel mass in one go.
  • Change of weather (sudden change of atmospheric pressure).
  • You bought a different brand of oil or gasoline.
  • During prolonged storage.
  • The screws unscrewed on their own after vibration.
  • The gasoline consumption increased, the carburetor began to overflow fuel.
  • The appearance of soot on the electrodes of the internal spark plugs of the device.
  • No more gasoline is getting into the cylinders.
  • The engine frequently stalls or doesn’t pick up enough revs.

What are the faults and how to recognize them?

One of the problems of failure of the grass trimmer engine can be a mesh filter. Only two breakdowns can be attributed to this element:

To identify the exact cause, you need to do a number of the following actions:

  • Unscrew the fuel air lock cover to remove the strainer. If dirt is found on the part, it should be washed in fuel or thoroughly blown out. If you see serious damage to the strainer body, you should install a new one without a second thought.
  • If the compressor’s fuel connection is broken, you should have this part checked. It most often requires periodic replacement due to its low durability.
  • Use acetone or gasoline to remove blockages from the carburetor’s starting part. You can also blow the components of the device with compressed air. this is the easiest and most convenient way of repair.

Important! The base of the throttle, inlet and outlet valves, the connection points of all parts of the carburetor can be checked with a simple action. lubricate the problem area with soap foam.

Self-adjusting the carburetor on the trimmer

The following steps are recommended before adjusting the gasoline mower:

  • Clean and flush the engine.
  • Check the suitability of the spark plugs.
  • Remove dust and dirt from the air filter or replace it with a new one.
  • Put a cord of suitable diameter in the trimmer roller or install well-sharpened blades.

After installing the cutting parts and starting the fuel engine carburetor needs to warm up within 10 minutes. In case the cutting attachment rotates when the engine is idling reduce the engine rpm.

Adjusting the carburetor on a trimmer is a difficult and time-consuming job. To tune it properly you only need information from our informative article. And in order to do everything properly, use the video, which clearly shows the whole process.

How it works

The air flow into the throttle tube increases or decreases depending on its position. From the fuel chamber, the gasoline enters into a special tube through a nozzle. The float is a device that regulates the fuel supply, its level determines the volume. Gasoline, fed through the nozzle, under the action of the pressure difference, mixes with the air. This is how you get the air-fuel mixture to run the engine.

Please note! Wrong fuel composition may be due to a lack of gasoline or air. this means that the throttle or float position has to be adjusted. The engine can also stall because of the nozzle, but it is a more serious failure.

Adjusting the lawnmower carburetor

Adjusting the carburetor

The next step is to adjust the idle stroke. And for that little by little unscrew the extended nut, which is needed for tensioning the cable when you press the throttle button on the lever.

The point of this adjustment is to achieve an optimal free stroke of no more than 2 mm.

As a result of this setting, when you press the throttle button on the handle, the choke should open almost completely. Screw the second nut all the way in. That is, let’s stop the whole thing.

The next step is to adjust the gasoline adjustment screw. Screw this screw all the way in and then unscrew it 1.5 turns.

Replace the filter housing and the air filter, screw in the spark plug and then try to start the brushcutter. If everything is operating correctly continue with the adjustment.


Electric and gasoline trimmers have typical breakdowns and malfunctions. For devices powered by the internal combustion engine, these are:

Weed Eater Won’t Start! How to FIX Weedeater that bogs down!

  • problems in the carburetor;
  • engine breakdown;
  • problems with the fuel system;
  • Breakdown of the gearbox, starter, muffler;
  • clogs;
  • Air filter failure;
  • problems with the ignition coil.

Electrical units have specific breakdowns:

With uncomplicated problems, you can make repairs to the grass trimmer with your own hands.

Why the grass trimmer won’t start

The most common reason that the unit does not start is the use of low-quality fuel. The choice of gasoline grades below AI-92 can put the lawnmower out of commission. If quality fuel is used, you need to look for other causes. To do this, thoroughly check all nodes and systems. To be checked:

The device may not start after prolonged idle time. Before you start the weed trimmer, you should read the instruction manual carefully. The solution to many of the problems are listed there.

If it stalls when you press the gas

There are several reasons why a grass trimmer stalls when you press the gas:

  • The first cause is a carburetor malfunction.
  • Fuel valve clogging.
  • Check valve blockage.
  • Loose and slack carburetor cable or slack fuel intake hose.

To avoid the described problems with the lawnmower, you need to carefully monitor the condition of the device and its units. Timely cleaning, washing of the unit and parts can extend its life.

Starter failure

The most difficult breakdown of the starter happens when the rope breaks and winds it on the flywheel of a running engine. Spring tension can break and pulley can come loose. In this case only a complete replacement of the part will help. Such a breakdown rarely occurs. common:

In this case it is easy to repair the starter by yourself. The manufacturer has prepared step-by-step instructions for this.

Husqvarna 128LD 28cc carb adjustment

Gearbox Repair

Care for the gearbox of a brushcutter is to lubricate the unit in a timely manner. Failure to do so may result in rapid wear of the gears and jamming of the gear module.

The main faults of the grass trimmer gearbox:

  • Strong heating of the transmission unit due to the use of low-quality lubricant or its absence;
  • shaft seizing due to rotation of worn bearings;
  • The gearbox is subject to misalignment or comes loose from the shaft because the housing is damaged;
  • No rotation of the output shaft with the blade due to wear of the teeth on the gears.

This can be caused by poor or no lubrication. Another cause of gearbox failure is the operation of the grass trimmer at the limit of its capabilities and the ingress of foreign objects. To replace the defective bearing, the gearbox must be disassembled.

Peculiarities of repair of electric models

Electric models of mains-powered trimmers have several main assemblies:

Each power trimmer unit has specific problems. On the mechanical side, they depend on the presence of a fishing line used as the cutting element. Causes of stopping work:

The electric part of the brushcutter can be diagnosed with the help of special tools:

A blowtorch is needed to fix problems.

  • Faulty power cable;
  • Problems with the socket and plug;
  • failure of the control knob;
  • burnout of the starter coil, it is necessary to replace the motor;
  • broken contacts can be repaired yourself with a blowtorch.

How the carburetor of a gasoline trimmer works

It is almost impossible to cover all the different carburetors, produced by manufacturers of gasoline trimmers. But, since the construction of this module, as well as its principle of operation is largely similar between different models, it is possible to make a generalized description of the processes that occur in the carburetor. This information will allow the user to understand the principles of operation of the device, to eliminate arisen failures and to operate it correctly.

The base of the grass trimmer carburetor is a one-piece aluminum housing. Below is a diagram of this unit.

At the bottom of it, there is a diffuser which is also called Venturi nozzle (18). The air is sucked in by the engine through this nozzle.

The smaller is this orifice, the higher is the air speed and the higher is the vacuum in the area with the smallest diameter.

There are fuel ducts (11,12) in the upper part of the diffuser. Through these channels, the air flow, draws the gasoline. The fuel pump itself, the nozzles and the system used to adjust the fuel/air mixture can be inbuilt or external mounted.

The restrictor choke (9) controls the amount of air drawn into the carburettor. Its quantity affects the power that an engine develops. The choke (7) is for the cold start. It must be closed if you want to start the machine. After the engine has started, it needs to open, otherwise the engine will immediately stall.

A pulse channel (1) connects the pulse chamber of the pump to the engine crankcase, namely its internal volume. The piston in the cylinder, by reciprocating motion, successively changes the pressure in the crankcase (vacuum or pressure increase). Pressure differential forces the diaphragm (4) to move. Therefore the pump operation is synchronized with the engine operation.

It is the diaphragm (4) that draws petrol from the tank. The petrol enters the carburettor through the connection (2). Then, its path goes through the inlet valve (3), the outlet valve (5), through the strainer (6), the fuel channel (10), passes the needle (14) and fills the chamber (16) that has the control diaphragm (18).

The valve (14) is connected to the diaphragm (18) by the lever (17). The cavity below the diaphragm communicates with the ambient air through port (19).

The function of the device is as follows.

  • During suction stroke a vacuum is created in the diffuser. This fact causes air suction. The position of the throttle valve (9) determines the amount of air entering the carburettor chamber, as well as the engine power and the number of its revolutions.
  • At this time through the nozzles (11,12) fuel is sucked from the chamber (16), after which it is mixed with the flowing air. Gasoline begins to atomize when it mixes with the air. The air/fuel mixture is thus created.
  • The ready mixture is pushed into the cylinder, where it is compressed by the rising piston and ignited at its highest point by a spark produced by the spark plug.
  • As the volume under the pilot diaphragm (18) is connected to the ambient air through the passage (19), the diaphragm moves upwards and opens the valve (14) with the lever (17). After the valve (14) is opened, a new portion of fuel enters the chamber (16).
  • after the chamber (16) is filled, the diaphragm (18) returns to its original position and the valve (14) closes.

Further, when the motor is running, all the processes described above are repeated. A screw (13) is used to adjust the amount of fuel entering the diffuser through the jets. A screw (15) is also used to adjust the idle speed. unscrewing the regulators enriches the fuel mixture, and tightening the regulators impoverishes the mixture. Also in some models of carburetors you can adjust the engine idle speed with the quantity regulator. It is usually located on the outside and when screwed in rests against the lever attached to the axle of the throttle.

adjust, carburetor, gasoline, trimmer, trouble, inlet

Thus, using 3 adjusting screws it is possible to achieve maximum engine performance and smooth operation of the engine at any ambient temperature and even in mountainous areas.

The lawnmower described above is mainly designed for lawn care. It is perfect for mowing the lawn. If you install a special knife on it, the equipment will be able to cope with rough grass, nettles and dried out brushwood. Adjusting the carburetor grass trimmer Huter. Adjusting the carburetor on the STIHL 55 lawnmower. Quite often the described version of the equipment is compared with the FS 38. These mowers differ in power.

The model described in this article has an ergonomic handle and a straight shaft. When working, you can use the manual fuel suction function, which allows you to make a start in the mode of the cool motor is even sharper.

Before making a purchase to evaluate not only the price, but also some other features of lawnmowers. Among them, in particular, should be allocated power, which will determine the performance of the work. An important factor is the device handle.