Intake needle wear
The inlet needle fails, as a rule, due to the presence of abrasive particles in the fuel fluid.
- the tightness of the inlet needle seat is disrupted;
- there is a leakage of a combustible mixture;
- there are malfunctions in the engine operation associated with re-enrichment of the fuel mixture.
Also, the inlet needle may just jam.
A jammed inlet needle can cause dirt in the fuel or a long idle period.
Throttle and choke shaft wear
The air and throttle shaft can wear out for the following reasons:
- insufficient and improper maintenance of the air filter;
- the air filter is damaged;
- the air filter is not suitable for this unit.
Due to the ingress of poorly cleaned air, the shaft wears out and can break. Broken shaft parts can enter the combustion chamber or crankcase and cause serious damage to the entire piston system.
To eliminate problems with air purification, it is necessary to replace the defective filter or flush the existing (serviceable) one. The filter must be washed in soapy water and dried.
Deformation of the control diaphragm
The membrane can undergo deformation during prolonged operation of the unit and when using aggressive fuels.
Failure of normal adjustment due to a defect leads to:
- damage to the piston;
- difficulties when starting up;
- depletion of fuel;
- improper engine operation.
Intake Adjustment Lever Problem
This problem can occur if the adjusting arm is not properly installed or if it is bent before installing. As a result, the contact surface takes the wrong position, which disrupts the additional fuel supply.
Clogged strainer
The strainer can become dirty if contaminated fuel enters through a fuel hose or a defective pickup head. In the photo below you can see what a clean filter looks like and a dirty one (parts are separated by a line).
Correcting the malfunction will require thorough cleaning and rinsing of the strainer. It is also recommended to blow compressed air through all holes in the grass trimmer carburetor housing.
Common carburetor malfunctions
Failure of the grass trimmer carburetor is caused by the use of poor quality gasoline, a damaged air filter, and accumulation of dirt in the chamber of this unit. Most often, it is quite possible to repair the carburetor with your own hands. Listed below are typical brushcutter carburetor malfunctions.
Fuel pump problems
A common malfunction that “pursues” the fuel pump is the deformation of the pump membrane. For this reason, it does not fit properly and the pump passages are not sealed.
The reasons for membrane deformation can be the following:
- continuous operation of the grass trimmer;
- use of unsuitable fuel;
- ingress of gases into the impulse channel.
As a result, diaphragm damage reduces pump performance and, as a result:
- depletion of the combustible mixture occurs;
- it is difficult to start the engine;
- there are interruptions in the operation of the motor;
- the piston is damaged.
Also, the above-described consequences for the engine can cause clogging of the pump cavity on the impulse side. In this case, dirt enters the membrane through the impulse channel.
To remove the blockage, you will have to disassemble the carburetor and clean the membrane.
How the benzotrimmer carburetor works and works
It is almost impossible to cover all types of carburetors produced by manufacturers of gas trimmers. But, since the design of this module, as well as its principle of operation, is largely similar between different models, a generalized description of the processes occurring in the carburetor can be made. This information will allow the user to understand the principles of operation of the device, eliminate the malfunctions that have arisen and operate it correctly.
The grass trimmer carburetor is based on a one-piece aluminum body. Below is a diagram of this block.
At the bottom of it, there is a diffuser, which is also called a Venturi nozzle (18). Air is drawn in by the motor through this nozzle.
The smaller this hole, the faster the air flows, and the higher the level of its rarefaction in the zone with the smallest diameter.
In the upper part of the diffuser there are fuel channels (11,12). Through these channels, the air flow draws in gasoline. The fuel pump itself, jets and the system used to regulate the supply of a mixture of fuel with air can be built-in or installed externally.
The throttle valve (9) controls the amount of air sucked into the carburetor. Its amount affects the power that the engine develops. The damper (7) is used for cold starting. It must be closed if you are going to start the unit. After the engine has started, it must be opened, otherwise, the engine will immediately stall.
The impulse channel (1) connects the impulse chamber of the pump to the engine crankcase, namely, to its internal volume. The piston located in the cylinder, producing reciprocating movements, successively changes the pressure in the crankcase (vacuum or pressure increase). The pressure drops force the diaphragm (4) to move. Therefore, the operation of the pump is synchronized with the operation of the engine.
The suction of gasoline from the tank occurs precisely with the participation of the membrane (4). Gasoline enters the carburetor through the union (2). Further, its path lies through the inlet valve (3), the exhaust valve (5), through the mesh filter (6), the fuel channel (10), passes the needle (14) and fills the chamber (16), which has a control diaphragm (18).
How To Adjust the Idle Speed Screw on a Trimmer/Blower
The valve (14) is connected to the diaphragm (18) by means of a lever (17). The cavity, which is located below the membrane, is connected to atmospheric air through the hole (19).
The device functions as follows.
- A vacuum is generated in the diffuser during the suction stroke. This fact causes air leaks. The position of the throttle valve (9) determines the amount of air entering the carburetor chamber, as well as the engine power and the number of its revolutions.
- At this time, fuel is sucked in from the chamber (16) through the jets (11,12), after which it is mixed with the flowing air. Gasoline, mixing with air, begins to spray. Thus, an air-fuel mixture is created.
- The finished mixture enters the cylinder, where it is compressed by the rising piston and ignited at its highest point from the spark generated by the spark plugs.
- Since the volume under the control diaphragm (18) is connected to atmospheric air through the channel (19), the diaphragm goes up, opening the valve (14) by means of the lever (17). After opening the valve (14), a new portion of fuel enters the chamber (16).
- After the chamber (16) is full, the diaphragm (18) returns to its original position, and the valve (14) closes.
Further, when the motor is running, all the above processes are repeated. A screw (13) is used to adjust the amount of fuel entering the diffuser through the nozzles. The screw (15) is also used to adjust the idle speed. When the regulators are twisted, the fuel mixture is enriched, and when the regulators are twisted, the mixture becomes lean. Also, in some models of carburetors, you can adjust the idle speed of the engine with a quantity regulator. It is usually located outside and, when twisted, abuts against a lever attached to the throttle shaft.
Thus, using 3 adjusting screws, you can achieve maximum engine performance, as well as adjust its smooth operation at any ambient temperature, and even in mountainous areas.
Grass trimmer carburetor. How to properly adjust the grass trimmer carburetor.
On trimmers, in addition to electric motors, gasoline internal combustion engines are installed. This mechanism requires special attention to itself, since if it is incorrectly configured, it will either refuse to work, or will work intermittently and loss of power. Basically, engine tuning is about adjusting the fuel flow, and this is done using the grass trimmer carburetor.
The standard design of any gasoline grass trimmer necessarily includes a fuel system, the basis of which is the action of a regular carburetor. Its structure and initial principle of operation are almost the same for all brushcutters, regardless of their design features and purpose.
The brushcutter carburetor consists of an all-metal aluminum body that protects the internal components of the unit from moisture, fine debris and dust. In the lower part of the body there is a built-in diffuser, the second name of which is “Venturi nozzle”. The main function of this standard part is to supply air in the amount required by the fuel unit to enrich the fuel. A diffuser works according to a simple principle: the smaller its diameter becomes, the more intensively the air is sucked in. This is due to the fact that in the area of the smallest diameter, the level of air discharge becomes maximum.
The upper part of the built-in factory diffuser is pre-equipped with fuel pipes, through which, under the influence of air, the fuel mixture is drawn in. The rest of the carburetor parts: standard adjusting screws and a fuel pump, can be located both inside and outside the carburetor.
The device of the carburetor of the brushcutter includes a throttle valve, the main task of which is to regulate the volume of intake air. The larger the amount of air, the higher the power rating of the grass trimmer. Another function of the damper is to facilitate cold starting of the engine. If the mower is starting up for the first time after a long period of inactivity, the shutter must be closed. Immediately after starting the engine, the part must be opened, otherwise the internal combustion engine will stall.
The grass trimmer carburetor is equipped with an impulse channel that connects the internal cavity of the engine crankcase with the impulse chamber of the pump. The piston located in the engine cylinder creates reciprocating movements, which leads to gradual changes in pressure inside the crankcase. At the same time, the membrane is set in motion. Thus, the action of the pump is fully synchronized with the operation of the power unit.
The diaphragm of the standard carburetor takes an active part in the suction of fuel. It enters the fuel unit through the fitting. The fuel then passes through the integrated inlet and outlet valves, then through the strainer and fuel pipe. The fuel then flows next to the needle and gradually fills the chamber equipped with the control diaphragm.
The stock trimmer carburetor valve is connected to the diaphragm using a lever. Below the built-in membrane there is a cavity into which air is sucked in through a special opening.
The lawn mower carburetor works on this principle in stages. This ensures continuous operation of the fuel unit and uninterrupted fuel supply to the cylinder of the standard power unit.
When is the carburetor setting of the household grass trimmer required? Adjust the built-in grass trimmer carburetor when:
- running in a new engine, during which 4 to 5 liters of fuel mixture were used;
- sudden changes in the weather;
- changes in the air pressure. for example, when the mower is often used in mountainous areas;
- long-term simple grass trimmer;
- intensive growth of loads on the power unit of brushcutters;
- arbitrary unscrewing of the built-in adjusting screws of the carburetor. this causes increased vibration of the internal combustion engine;
- changes in the quality of the components of the fuel mixture;
- pouring fuel with a carburetor, resulting in an increase in fuel consumption;
- the regular appearance of a thick layer of resinous deposits and carbon deposits on the surface of the electrodes of the standard spark plug for the grass trimmer;
- starting the engine and its arbitrary shutdown or slow set of revolutions;
- lack of fuel flow into the cylinder of the power unit;
- increase in the volume of emitted waste gases.
The lack of timely adjustment of the carburetor threatens serious damage to the grass trimmer, up to the complete failure of its factory engine.
Do-it-yourself lawn mower carburetor adjustment. Periodic adjustment of the grass trimmer carburetor must be performed with a serviced and fully functional power unit. Before starting the procedure, the operator must thoroughly rinse the internal combustion engine parts and inspect its CPG for burrs or other defects. In addition, you will need to clean or change the spark plug, as well as rinse the filter elements in the brushcutter design.
When adjusting the carburetor, the mower’s engine must be running under a certain load. It is best to install a cord of the appropriate diameter or cutting blades on the grass trimmer.
After installing the cutters, the operator should start the engine of the grass trimmer and let it run for about 10 minutes. If, during the operation of the power unit at idle, it was noticed that the cord or knife rotated, then it is necessary to reduce the speed generated by the motor. To do this, turn the lower adjuster, often marked with the letter “T”, to the left, until the installed cutter comes to a complete stop. Further configuration of the fuel assembly is as follows:
- The “L” regulator, located on the right, is responsible for enriching the fuel mixture with air when the engine is running at low revs. The position of this screw must be adjusted first. To do this, the operator will need to achieve maximum engine speed when idling. to do this, turn the screw “L” one by one to the right or left. As soon as the maximum speed is reached, the screw will need to be turned 1/2 turn to the left;
- The screw “T” or “LA” is required to adjust the idle speed. While turning it to the left, the speed of the power unit will decrease, and when turning to the right, it will increase accordingly;
- The “H” regulator on the left is responsible for enriching the fuel mixture with air when the internal combustion engine of the grass trimmer is operating at high rpm. This screw is also needed to adjust the engine power and the amount of fuel consumed. Its position is adjusted by turning the screw to the right or left side until the maximum permissible engine speed is reached. After that, the screw “H” will need to be turned 1/2 turn to the left.
Common carburetor malfunctions. Failure of the grass trimmer carburetor is caused by the use of poor quality gasoline, a damaged air filter, and accumulation of dirt in the chamber of this unit. Most often, it is quite possible to repair the carburetor with your own hands. Listed below are typical brushcutter carburetor malfunctions.
Fuel pump problems. A common malfunction that “pursues” the fuel pump is the deformation of the pump membrane. For this reason, it does not fit properly and the pump passages are not sealed.
The reasons for membrane deformation can be the following:
- continuous operation of the grass trimmer;
- use of unsuitable fuel;
- ingress of gases into the impulse channel.
As a result, diaphragm damage reduces pump performance and, as a result:
- depletion of the combustible mixture occurs;
- it is difficult to start the engine;
- there are interruptions in the operation of the motor;
- the piston is damaged.
Also, the above-described consequences for the engine can cause clogging of the pump cavity on the impulse side. In this case, dirt enters the membrane through the impulse channel.
To remove the blockage, you will have to disassemble the carburetor and clean the membrane.
Strainer clogged The strainer can become clogged if contaminated fuel enters through a defective fuel hose or pickup head. In the photo below you can see what a clean filter looks like and a dirty one (parts are separated by a line).
Correcting the malfunction will require thorough cleaning and rinsing of the strainer. It is also recommended to blow compressed air through all holes in the grass trimmer carburetor housing.
The adjusting lever is defective This breakdown occurs when the contact surface of the lever wears out.
The abrasion of the contact surface occurs due to the presence of abrasive particles in the gasoline or due to strong vibration of the engine during operation. This defect in the adjusting lever causes problems with the intake, as well as improper idling of the engine.
Inlet needle wear The inlet needle is damaged, usually due to the presence of abrasive particles in the fuel fluid.
- the tightness of the inlet needle seat is disrupted;
- there is a leakage of a combustible mixture;
- there are malfunctions in the engine operation associated with re-enrichment of the fuel mixture.
Also, the inlet needle may just jam.
A jammed inlet needle can cause dirt in the fuel or a long idle period.
Clogged control cavity If dirt accumulates in the control cavity, the inlet needle cannot close the hole tightly and a lot of fuel pours into the chamber.
This causes over-enrichment of the fuel and the engine starts to malfunction. It is necessary to disassemble the carburetor and clean the cavity of the control membrane.
Deformation of the control diaphragm The diaphragm can be deformed during prolonged operation of the unit and when using aggressive fuels.
Failure of normal adjustment due to a defect leads to:
Easy Weed Eater Carburetor Adjustment To FIX. BOGGING DOWN. STARTING PROBLEMS. ROUGH IDLE
- damage to the piston;
- difficulties when starting up;
- depletion of fuel;
- improper engine operation.
Inlet Adjustment Lever Problem This problem can occur if the adjustment lever is not installed correctly or if it is bent before installing. As a result, the contact surface takes the wrong position, which disrupts the additional fuel supply.
Correct Way To Adjust Or Tune The Carburetor On A Weedeater / Grass Trimmer
Flap wear The throttle and choke valves are mainly worn out by the presence of abrasive particles in the air. Defective dampers look like they have been sandblasted.
As a result of valve wear, engine performance decreases, malfunctions appear in its operation, piston rings, piston and cylinder coating wear out.
Throttle and choke shaft wear The air and choke shaft can wear for the following reasons:
- insufficient and improper maintenance of the air filter;
- the air filter is damaged;
- the air filter is not suitable for this unit.
Due to the ingress of poorly cleaned air, the shaft wears out and can break. Broken shaft parts can enter the combustion chamber or crankcase and cause serious damage to the entire piston system.
To eliminate problems with air purification, it is necessary to replace the defective filter or flush the existing (serviceable) one. The filter must be washed in soapy water and dried.
How to make the correct adjustment Before you start adjusting the carburetor of the grass trimmer, 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, wring 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 during the tuning process the engine has at least some kind of load. After installing the cutting tool and starting the gasoline engine, let it warm up for 10 minutes.
If at idle speed 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 speed control, often marked with the letter “T”. But, for example, on a STIHL trimmer, this screw may be marked “LA”.
So, turn the idle speed control to the left until the trimmer head comes to a complete stop.
To adjust the carburetor, 3 regulators (screws) are used.
- The right L regulator adjusts the fuel mixture enrichment level at low revs. It needs to be regulated first. Achieve maximum idle speed. This is done with the L knob by turning it left and right. After finding the point of maximum speed, return the regulator half a turn to the left (counter-clockwise).
- The lower T (LA) adjuster is used to adjust the idle speed. Turning it to the left, the engine speed will begin to decrease, and when turning the regulator to the right, the engine speed will increase.
- The left regulator H is responsible for enriching the combustible mixture at high speeds. The enrichment setting completes the carburetor setting. Also, using this regulator, 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 nuisance, adjustment will be required. With the engine running, give full throttle, then turn the regulator “H” to the right until the speed starts to decrease. After that, the “H” regulator must be slowly scrolled to the left until you hear the uneven operation of the engine. Then you should turn the knob “H” to the right until you hear the smooth operation of the motor.
After carrying out the above steps, the carburetor setting can be considered complete. After correct adjustment, the engine should confidently pick up speed, a little quarter at maximum speed, and when idling, the cutting tool should not turn. This manual is suitable for adjusting carburettors on Huter, Patriot and other petrol cutters.
There are also carburetors without a screw, which is responsible for enriching the fuel mixture at low speeds. That is, they have only 2 adjusting screws: an idle speed regulator and a fuel mixture quality regulator at high speeds.