How to adjust the carburetor needle brushcutter

The device carburetor gasoline grass trimmer trimmer

Adjusting the carburetor of a brushcutter. a process that must be mastered for the full operation of the grass trimmer. Grass trimmer. a completely uncomplicated device, which can break down only in a few places and require mechanical repair or replacement parts. Adjusting the float-type brushcutter carburetor device may require knowledge of certain subtleties. 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 float-type grass trimmer. 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 roughly similar to the malfunctions that overtake the carburetor in the car:

  • the engine can shut down immediately after you have managed to start it. The reason is that not enough gasoline is being supplied. This is called “poor” fuel;
  • Too much gasoline leads to incomplete combustion, excessive mixture density and uneconomical consumption.

Carburetor repair

Important! Adjust the carburetor has to be under different circumstances: a 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 from strong vibration of the body. Some owners prefer to tune the module before each use to make sure it is working properly.

Basic troubleshooting

Faults in the carburetor of brushcutter or grass trimmer, despite the relative ease of fixing them, sometimes require a long search by the method of elimination. The main causes are as follows:

The most recurring breakdown. wear, rupture of the diaphragm. As a consequence, its loose. The fuel passages are not sealed at certain stages of the engine cycle. The reasons are as follows:

  • You run the brushcutter or trimmer for too long without stopping;
  • you fill the tank with low-quality fuel;
  • Exhaust gases enter the impulse line.
adjust, carburetor, needle, brushcutter

A deformed diaphragm has several bad consequences:

  • Not enough gasoline or oxygen in the combustible mixture created;
  • Engine starts after 10 or more unsuccessful attempts;
  • the engine rattles and clatters when running, etc. д.;
  • The operating piston deforms.

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

Wear of the lever’s contact surface. the consequence of not completely cleaned fuel, which has caught grains of sand or particles of clay, metal or other inclusions that are not soluble in liquid hydrocarbons. There is a problem with fuel injection, the engine without load functions with interruptions.

Inlet needle breaks because of metal particles and rock in the gasoline. As a result, the inlet needle seat does not seat tightly and the fuel mixture leaks. There is too much air in the mixture created by the carburetor, which can cause the engine to “sneeze” during operation. Finally, the needle may stall because of poor-quality gasoline, or the machine has been idle for a long time.

Deposits may accumulate in the adjustment compartment. The needle does not close the hole completely and a lot of gasoline enters the fuel chamber. the engine overflows, possibly flooding the spark plugs as well. Because of this, the gasoline-air mixture contains an increased amount of gasoline vapor. The efficiency drops noticeably.

The diaphragm is often deformed (and sometimes torn) because the brushcutter or weed trimmer runs continuously for several hours. If you overdo it, it is more likely that the diaphragm will be damaged. New breakdowns will come out of the horn of plenty:

  • The piston is broken;
  • the number of attempts of unsuccessful engine start will increase dramatically;
  • the fuel mix contains too little gasoline;
  • The power output (thermal output) will drop drastically.

Adjustment lever seizing up due to improper installation, accidental bending. The contacting facet will get the wrong position. It will disrupt additional injection of gasoline.

The flapper is worn out

Throttle and air valve become unusable because of dust, metal particles, etc., in the air stream. д. Damaged flaps look like parts that have been blasted with sand. Due to the flap wear the efficiency of the engine will decrease, breakdowns will be detected. Piston and cylinder wear out.

The filter may not be compatible with your brushcutter or trimmer model. Eventually the motor shaft will suffer. pieces of it will get into the motor channels, causing the piston to break.

When the adjustment is too coarse (you can’t precisely set the parameters), the springs on the adjusting screws are to blame. The manufacturer of the brushcutter or grass trimmer may have supplied excessively thick and stiff springs. Find others at either workshops that repair similar equipment, or purchase one from any dealer or official representative of the company that made the motor for your grass trimmer or mechanical grass trimmer mower.

The primer is broken

Primer is a hand-operated mini-pump for forcing fuel into the carburetor. You may need to pump 20 ml of gasoline manually to start the engine successfully.

When the carburetor of a residential grass trimmer needs adjustment?

Adjust the grass trimmer’s built-in carburetor at:

  • The new engine was run-in, during which 4 to 5 liters of fuel mixture were used;
  • sudden changes in the weather;
  • Changing the air vacuum. for example, when the lawnmower is often used in mountainous terrain;
  • prolonged idle time of the grass trimmer;
  • intensive increase in the load on the brushcutter power unit;
  • Unintentional twisting of the carburetor adjustment screws causing increased engine vibration;
  • changes in the quality of the fuel mixture components;
  • overfilling of fuel by the carburetor, the consequence of which is an increase in fuel consumption;
  • Regular appearance of a thick layer of tarry deposits and carbon deposits on the surface of the spark plugs of the standard spark plug of the trimmer for grass;
  • starting the engine and its arbitrary shutdown or slow revs;
  • absence of fuel inflow into the power unit cylinder;
  • higher exhaust gas emissions.

Lack of timely adjustment of the carburetor can cause serious damage to the grass trimmer, up to the complete failure of its factory engine.

lawn mower carburetor adjustment with your own hands

Periodic adjustment of the grass trimmer carburetor should be performed on a serviced and fully serviceable power unit. Before starting the procedure, the operator must thoroughly wash the parts of the engine and inspect its CPG for burrs or other defects. In addition, it will be necessary to clean or change the spark plug, as well as wash the filter elements in the construction of the brushcutter.

During the carburetor adjustment, the lawn trimmer engine must work under a certain load. It is best to install a cord of appropriate diameter or cutting blades on the grass trimmer.

After installing the cutting elements, the operator must start the grass trimmer’s engine and let it run for about 10 minutes. If during the operation of the power unit at idle rpm it was noticed that the cord or blade is rotating, then it is necessary to reduce the speed created by the motor. To do so turn the control knob, often marked with the letter “T”, to the left until the cutting unit has come to a complete standstill.

Further scheme of adjustment of the fuel unit is as follows:

  • The regulator “L” located on the right side is responsible for enrichment of the fuel mixture with air during engine operation at low revolutions. The position of this screw should be adjusted first. To do this the operator needs to achieve maximum engine rpm when idling. to do this turn the screw “L” alternately to the right or left side. Once maximum RPMs are reached it will be necessary to turn it 1/2 turn to the left;
  • The screw “T” or “LA” is necessary for adjusting the idling speed. Turning it to the left will decrease the engine RPM and turning it to the right will increase it;
  • The regulator “H” on the left side is responsible for air enrichment of the fuel mixture when grass trimmer engine works at high revolutions. This screw is also used to set the engine power and fuel allowance. Adjustment of its position is performed by turning the screw to the right or left side until the maximum permissible engine speed. You will then need to turn the “H” screw 1/2 turn to the left.

Performing these actions in turn will allow you to properly adjust the trimmer fuel assembly for grass, without risking to exceed the allowable load on its main working mechanisms.

When the carburetor needs to be adjusted?

Stable working of your brushcutter carburetor depends greatly on correct carburetor tuning.

Adjustment is required in the following cases:

  • After running in a new grass trimmer, when 4-5 full tanks of fuel have been used during operation;
  • If the operator frequently changes the brand of gasoline used for refueling;
  • As a result of a sudden change in the weather;
  • Prolonged storage of your grass trimmer;
  • As a result of arbitrary unscrewing of adjusting bolts of trimmer, caused by strong vibration of its engine;
  • Due to a sharp increase in the amount of fuel used by your trimmer.

You will also need to adjust the carburetor on your brushcutter if the tool’s spark plug quickly becomes soiled or if there is a sudden increase in the amount of exhaust fumes discharged from the trimmer.

Adjusting the lawn trimmer carburetor with your own hands

Regardless of the model of the garden tool, adjusting the grass trimmer carburetor requires careful prior preparation. The owner of a brushcutter will need to check the spark plug, air filter and the carburetor itself. If there is dirt, all the elements must be cleaned, or if necessary, replaced.

The grass trimmer comes standard with 3 adjustment bolts. The first of them. marked with the letter L, and serves to adjust the engine when it works at low rpm. The second bolt is marked with the letter H, and is required for adjustment of the engine when it works at the highest rpm. The third bolt can be marked with the letters T or LA. with its help, the operator can adjust the engine’s work at idle rpm.

The process of adjusting the carburetor of a brushcutter is as follows:

  • First you need to do a series of actions with the adjusting bolt L. This is accomplished by turning it clockwise as far as it will go. After that the bolt L should be turned half a turn in the opposite direction. This will allow you to adjust the optimal oxygen enrichment of the fuel mixture at low engine speeds;
  • You will then adjust the idle speed of the engine. This is done by alternately turning the bolt T in different directions until the mowing head or blade stops turning;
  • Finally it is necessary to adjust the level of oxygen enrichment of the fuel at maximum engine speed. The H bolt should be turned clockwise as far as it will go and then back 1/2 turn in the opposite direction.

At the end, the operator must shut off the grass trimmer motor and start it up again. If it has been adjusted correctly, the brushcutter engine will go up in speed steadily when the throttle trigger is pulled and drop it quickly when the trigger is released.

Principle of operation of the carburetor

The brushcutter carburetor always works on the same principle.

The function of the node is as follows:

  • First, a certain vacuum is created in the diffuser as a result of the motor suction stroke, which leads to a suction of air masses;
  • Fuel then flows through the nozzles and the combustion chamber and mixes with the air. After enrichment with air, the gasoline is atomized gradually to create an air-fuel mixture;
  • Then the ready mixture enters the cylinder of the internal combustion engine, where it is affected by the piston. At the high point of the piston stroke, the fuel is ignited by a spark produced by the brushcutter’s spark plug;
  • Due to the fact that the inner cavity under the diaphragm by means of a channel is connected to the air from the environment, when the diaphragm rises the valve is opened. This causes the air to flow into the cavity under the diaphragm;
  • Once the chamber is filled with fuel mixture, the diaphragm quickly returns to its original position. The valve closes while filling with fuel.

the scheme of work of the node is repeated constantly, throughout the whole cycle of operation of the garden trimmer for grass.

adjust, carburetor, needle, brushcutter

When the carburetor needs to be adjusted?

A stable carburetor on your brushcutter depends to a large extent on correct carburetor settings.

Adjustment of the assembly is required in the following cases:

  • After running in a new grass trimmer, when 4-5 full tanks of fuel have been used during operation;
  • If the operator frequently changes the brand of gasoline used for refueling;
  • Sudden changes in the weather;
  • Due to prolonged storage of the grass trimmer;
  • As a result of an accidental unscrewing of the adjusting screws on the brushcutter caused by strong vibrations in the engine;
  • because of a sharp increase in the amount of fuel consumed by the trimmer.

Adjusting the carburetor of the trimmer will also be necessary in cases where the spark plug of the tool quickly becomes soiled, as well as a sharp increase in the volume of exhaust gases emitted by the trimmer.

Grass trimmer carburetor adjustment.

As a rule, the grass trimmer (lawnmower) should be adjusted according to the technical datasheet. In particular, the most correct will be to read the information exactly in the manual to your trimmer. It usually describes in detail how to adjust the lawnmower. If you don’t have a manual for your trimmer, you can use our tips.

Stages of adjustment of the lawn mower carburetor:

  • Low RPM L adjustment;
  • Adjustment of the idle speed with the LA (T) screw;
  • Adjusting the fuel flow at high rpm. H.

Adjusting the Fuel Flow. Low RPM (L).

First of all, the upper right L screw is adjusted, i.e. the amount of fuel supplied at low rpm is adjusted. For STIHL fs series trimmers, the L screw is turned all the way clockwise, then returned one full turn counterclockwise. Besides, such adjustment is also relevant to many other trimmers. Once you have done this, go to the LA (T) screw and turn it clockwise to increase revolutions and counterclockwise to decrease revolutions. It should also be noted that turning the screw counterclockwise adds fuel to the mixture, turning it clockwise reduces the amount of fuel in the mixture;

The second stage of the adjustment is the adjustment of the idle speed by means of the LA (T) screw, here the adjustment is done purely by ear. Turn the screw clockwise to increase the mower’s RPM and counterclockwise to decrease it. it is important to make sure that the mower head does not spin during idling. It should also be noted that the L and LA screws are adjusted in pairs, that is, changing the adjustments on one screw may require changing the adjustments on the second screw. After you have achieved a smooth operation of the engine with a minimum of vibration. go to the adjustment of H.

How the lawnmower carburettor works

The throttle valve determines the amount of air to be fed and this has a direct effect on the horsepower of the engine.

Fuel is sucked into the carburetor system by a pump (its diaphragm). Then flows through the connection on the carburetor. Then the fluid moves through the inlet and outlet valves of the pump. Filtered by the strainer. Fuel flows through the needle valve into the diaphragm chamber.

  • The air flows into the tube with an air divider (damper). The partition regulates the intensity of the airflow.
  • The fuel system is necessarily narrowed by a diffuser to increase the flow rate.
  • Gasoline through the float chamber and nozzle tube with a constriction. The float chamber adjusts the temporary volume of gasoline. The float chamber has a neutral pressure level, while the tube with a constriction is already low. Because of the pressure drop, the fuel flows through the nozzle.
  • Acceleration of airflow promotes the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the desired proportion or density is formed.
  • The air-fuel mixture enters the engine cylinder through the fuel tube.

The area of the open air flap determines the level of air density in the system. The wider the damper is open, the greater the fuel flow and power.

Simply put, adjusting the carburetor on a chainsaw is about creating an optimal fuel mixture through correct air supply.

When you need to adjust the carburetor of a domestic grass trimmer?

Adjust the built-in grass trimmer carburetor needs to be adjusted at:

  • The new engine was run-in, during which 4 to 5 liters of fuel mixture were used;
  • sudden changes in the weather;
  • changes in air vacuum. for example, when the lawnmower is often used in mountainous terrain;
  • prolonged idling of the grass trimmer;
  • intensive increase in the engine load on the brushcutter’s power unit;
  • arbitrary unscrewing of the carburettor’s internal adjusting screws. this causes increased vibration of the engine;
  • change in the quality of the fuel mixture components;
  • fuel overflow from the carburetor, resulting in increased fuel consumption;
  • regular appearance of a thick layer of tarry deposits and carbon deposits on the electrode surface of the standard grass trimmer spark plug;
  • engine starting and its random shutdown or slow acceleration;
  • lack of fuel supply to the power unit cylinder;
  • increased volume of exhaust gases emitted.

Lack of timely adjustment of the carburetor threatens a serious breakdown of the grass trimmer, up to the complete failure of its factory engine.

When you need to adjust the carburetor of a domestic grass trimmer?

Adjust the built-in grass trimmer carburetor when:

  • running-in of a new engine, during which 4 to 5 liters of fuel mixture have been used;
  • sudden weather changes;
  • changes in air vacuum. e.g. when you frequently use the lawnmower in mountainous terrain;
  • prolonged idling of the grass trimmer;
  • High strain on the brushcutter’s power package;
  • arbitrary unscrewing of the built-in carburetor adjusting screws. this causes increased vibration of the engine;
  • changes in the quality of the fuel mixture components;
  • Fuel overflow in the carburetor, resulting in increased fuel consumption;
  • Regular appearance of a thick layer of tarry deposits and carbon deposits on the electrode surface of the standard spark plugs of the grass trimmer;
  • starting the engine and its arbitrary shutdown or slow revs;
  • lack of fuel supply to the power unit cylinder;
  • increased volume of emitted exhaust gases.

Lack of timely adjustment of the carburetor can cause serious damage to the grass trimmer, up to the complete failure of its original engine.

How to adjust the carburettor on the gasoline mower

Before adjusting, the filters must be thoroughly cleaned according to the maintenance in the manual.

Further adjustment of the lawnmower carburetor with your own hands is done with the adjustment screws. There are three of them in total:

Right (L). adjustment of the fuel mixture for low revolutions.

Find maximum idling rpm. To do this, slowly turn the screw (L) to the right and left.

To adjust the carburettor, turn the screw a quarter of a turn anticlockwise.

Lower (T). is responsible for adjustment of engine at idle speed.

It is characteristic for the correct adjustment of the idle speed:

  • steady operation of the cold engine;
  • hot engine rpm is not excessive;
  • for the trimmer head a large RPM margin;
  • stable engine operation during changes of position (sudden raising or lowering of the blade).
adjust, carburetor, needle, brushcutter

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

The left screw (H) determines the overall adjustment of maximum rpm, engine power, temperature and gasoline consumption.

Adjust the lawnmower carburetor with the last screw as follows:

  • Open the throttle to full, with full throttle. Turn the propeller clockwise until the rpm drops (in this case, use your ear to guide you).
  • turn the screw as slowly as possible counterclockwise until the engine runs smoothly.
  • Then turn it back just a little bit, barely hearing a stable, steady running.
  • It is more convenient to review the operation of an experienced user for a clearer application of skills:

Interestingly, from the perspective of the author of the video, setting (its correctness) is determined by the color of the candle, not only the revs and engine stability.

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

The Chinese lawnmower does not start. Getting into the carburetor.

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“It doesn’t pump gasoline in the cylinder, you can squirt it on and then it shuts down”. these are the words with which many of our service center receives a lot of gasoline in the summer period.

Can you fix it?? Unfortunately not always We will try to tell you about the most common problems with this carburetor and how to fix them with your own hands.

Before you make any manipulations with the carburetor it is necessary to exclude the possible malfunctions that can affect the operation of the lawnmower (simulate not working or not tuned carburetor:

Fuel filter (hoses): no mechanical damage on the filter body, no dirt, good flow capacity

Air filter: no mechanical damage to the filter surface, no dirt, good air flow

Faulty ignition system: a functioning spark plug “paired” with the ignition module should ensure stable engine operation

A reliable exhaust system: the cylinder outlet and the muffler must not be clogged with soot. which would cause the weed whacker to “choke”, not revving up. giving the impression of a faulty carburettor.

Tightness of the crankcase. Crankshaft oil seals, rubber intake adapters, as a result of damage (natural wear) let extra air into the engine, which usually manifests itself in a strong overrevving and a failure to adjust the carburetor.

If, after checking all these nodes suspicion remains on the carburetor, you can proceed to its primary inspection. Conventionally speaking, after unsuccessful attempts to start the engine. unscrew the spark plug and it is “dry”

The disassembly of the carburetor should be performed on a clean bright surface in order not to lose small parts. The disassembly process can be recorded on a camcorder, so it is easier to produce reverse assembly.

What you can check with your own hands at home?

“Standard” version of a modern Chinese lawnmower. Has the same layout and many variants of manufacturers (Patriot, Forward, Green, Etalon, Prorab, Varyag and many others)

We remove the air filter cover by unscrewing the screw.

Next, unscrew the two screws that fix the air filter housing and remove it.

Next, unscrewing the nut fixing the cable, remove it from the throttle body. The screw, marked with an arrow, adjusts the idle speed on these carburetors.

The carburetor gasket should not be damaged, if necessary replace it.

This quality screw is adjusted by the manufacturer, by itself it can not “razreguliruyutsya. In the course of operation it is possible adjustment due to wear of piston group, but it will have “minimal values”.

As practice shows the factory value of this adjustment. 1.5 turns (If you “razregulated” it. twist fully and unscrew 1.5 turns). With this value, provided the serviceability of components trimmer for grass necessarily starts. After warm-up it may be necessary to adjust the propeller (should be stable at gas rpm))

There is no need to turn it unnecessarily!

The Chinese gasoline scraper carburetors. on the left for the engine capacity of 26 and 33cm³, on the right for the engine capacity of 43 and 52cm³. The design is the same, the difference is shown in the photo. They are the same.

At once we examine a condition of diaphragm blades. They must not be “bent” away from the plane of the carburetor. The diaphragm itself must not have any damage.

The diaphragm gasket also must not be torn or damaged.

The body of the carburetor is also not allowed to dirt or deposits that can clog the channels and affect the operation of the carburetor.

The diaphragm must be “intact” and have no damage on its surface.

“The “heel” of the diaphragm must not “twist

Pay attention to the “inlet needle area”. If there is any dirt or even traces of rust, be sure to clean everything.

The stroke of the needle should be smooth, without faltering or jamming.

To check the needle, press the “sandwich” to the carburetor. pour gasoline (carburetor cleaner) over the area of the needle (the excl. orange arrow)

At the fuel connector put the hose (yoke) on the connector (yoke). red arrow), blow air in, at the same time inspect the needle for air “bubbles.

adjust, carburetor, needle, brushcutter

If there are no bubbles, the needle holds, no problem. If there are bubbles disassemble further.

Loosen rocker arm fixing screw.

There is a spring underneath the coring head, be careful when disassembling, don’t lose small parts.

Take out the axle with the coring head, the needle and the spring.

I’d like to note the following: if the “seat” under the needle is broken, no amount of manipulation will help. you will have to replace the carburetor.

How to adjust the trimmer for grass on the brushcutter

Most modules have adjustment screws, and to understand their functionality is usually helped by a diagram:

  • L. for fuel supply at low rpm;
  • H. fuel supply at high rpm and its consumption;
  • T. adjusting the idle speed.

Adjusting the brushcutter, the production of which is Chinese, can cause difficulties due to the presence of only one screw, which is responsible for the idle stroke.

Important! The answer to the question of how to adjust the carburetor of a Champion lawnmower, it is better to see a video where a professional does it.