No Idle Trimmer
A gas brush or a trimmer with internal combustion engines require not only constant refueling of the fuel mixture of gasoline with oil, but also periodic adjustment of the supply of this fuel. The carburetor is responsible for supplying fuel to the cylinder of the brushcutter, the efficiency and productivity of the tool depend on the proper operation of which. If a malfunctioning (abnormal) engine operation is detected during operation, then the first step is to adjust the carburetor of the brushcutter. Before setting up the carburetor of the gas trimmer, we will first deal with its design.
Design of a petrol-trimmer carburetor and its purpose
Petrol scythes are equipped with two-stroke type internal combustion engines. To supply the air-fuel mixture to the engine cylinder, a carburetor is used. In the design of gasoline units. this is a key element without which the operation of the internal combustion engine is impossible. Moreover, this carburetor differs from the automobile device not only in size, but also in the principle of operation. In particular, this difference lies in the presence of a membrane, which plays the role of a gasoline pump. It is due to the presence of the membrane that the devices under consideration in the design of two-stroke internal combustion engines are called membrane.
Structurally, the entire mechanism is a small-sized part, inside of which there are channels, valves and membranes. The carburetor body is made of aluminum, and the internal device is shown in the photo below.
Before you adjust the carburetor with your own hands, you need to deal with all the components of the device in question. The carburetor of the brushcutter and trimmer 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 maximum speed
- Fuel channels (jets) of idling XX and medium revolutions
- Throttle. the opening value is adjusted by pressing the gas
- Impulse channel fitting. connects to the internal channel of the crankcase
- Inlet fuel channel (fitting) (2). provides fuel from the gas tank
- Membrane (4). responsible for the absorption of fuel from the gas tank
- Tank Suction Valve (3)
- The valve for supplying fuel to the carburetor channel (5)
- Filter element (6) or fuel fine filter
- Fuel channel (10)
- Needle valve needle (14). responsible for the fuel supply to the chamber of the control membrane
- The chamber is the fuel mixture, which is fed through the jets and the throttle to the cylinder
- Control membrane (18). manual primer fuel is provided
- Lever connected to the membrane (17)
- Idle adjustment screw (15)
- Screw for adjusting the amount of fuel supplied to the diffuser (13)
Having an idea of how the carburetor is arranged inside, it remains to be understood how it works. A detailed description of how a carburetor works on a two-stroke internal combustion engine using an example of a chainsaw is described in this material.
How does a petrol scraper carburetor work or how it works
The carburetor adjustment of the Chinese petrol scythe is completely identical to the setting of the lawn mowers of European, Russian and manufacturers. In order to cope with the task of adjusting the carburetor on gas scythes and gas trimmers, it is necessary to understand the principle of their functioning. How a carburetor works on a benzokos is described step by step and available below.
- The operation of the carburetor of the brushcutter begins with the supply of fuel through the channel, as shown in the diagram
- The fuel is sucked into the carburetor using a pulse channel connected to the crankcase. Due to rarefaction of air, the flexible membrane at number 4 is moved in the diagram above
- Through valves 3 and 5, fuel is supplied. Valve 3 is the inlet, due to which fuel is fed into the submembrane space, and valve 5 is the exhaust
- Then the fuel moves along the channel and, passing 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 membrane. When it is necessary to pump fuel to start the engine, it is necessary to act on the soft cover of the hand pump. When exposed, the needle opens and the chamber fills with fuel mixture
- When the engine starts (on cold), the opening of the needle occurs due to rarefaction with the air damper closed. This vacuum acts through the idle and high speed jets on the membrane 18
- The membrane acts through the lever on the needle valve, whereby the chamber is filled
- After starting the engine, the air damper opens, as a result of which the engine runs on a lean mixture, as the fuel mixes with air
- The fuel mixture, when the chamber is full, is supplied (sucked) through the idle and medium speed jets (when the engine is started)
- The throttle valve is shifted from the original position by 10-15 degrees
- When the work is carried out under load, the fuel begins to enter the chamber through the high-speed jet, and at the same time, the throttle valve is rotated by an angle of up to 90 degrees (depending on the force of pressing the gas). In all operating modes, an air damper must be opened, through which the fuel is mixed with air, and thereby the mixture ignites in the cylinder
Below is a diagram of the principle of operation of the carburetor chainsaw. Based on the scheme, you can not only understand the principle of operation, but also identify breakdowns and other malfunctions of the mechanism.
Video: No Idle Trimmer
When operating the tool, one more nozzle must be considered. This nozzle is located between the idle and full power channels. It is necessary in order to exclude severe depletion of the mixture, which occurs in the case of motor operation under partial load. In this situation, the occurrence of a badass pair. Through an additional channel (jet), the fuel is sucked into the chamber, whereby the fuel-air mixture is enriched. The following diagram shows an additional nozzle, which is indicated by the number 1.
Having an idea of the design of the membrane carburetor of the lawn mowers and the principle of operation, it will not be difficult to do it yourself. Adjustment screws are used to adjust the carburetor of the brushcutter. The diagram above shows two screws for adjustment, however, most modern models of gasoline trimmers are equipped with three screws. The presence of three tuning screws allows for more accurate adjustment, while achieving stable and uninterrupted operation of the internal combustion engine.
How to find out that the petrol scraper carburetor needs adjustment
Many craftsmen use gas mowers for a long time, and at the same time do not think about the need to adjust the carburetor of the tool. When is it necessary to adjust the carburetor on a gas mow or lawn mow? If you ask yourself this question, then surely there are changes in the motor operation not for the better. In order not to guess, and not to miss the moment of the need to adjust the carburetor, you should adhere to the following recommendations on the need for adjustment measures:
- After engine break-in. Usually a run-in lasts for 4-5 liters of fuel
- When a fuel mixture of a different composition is poured into the tank, that is, the type of oil (even its color) and the brand of gasoline change
- With changing weather conditions, however, this is more true for chainsaws, gas generators and motor pumps, which are operated not only in summer but also in winter
- If the brushcutter has not been used for a long time. The reason for the need for adjustment may be a winter break
- When fuel consumption rises
- If black soot is detected on the electrode electrodes
- In the absence of gasoline in 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-up and a “sluggish” set of revolutions
As you can see, there are enough reasons to adjust the carburetor of the lawn mowers. Usually, craftsmen who work with the tool for a long time, by ear, detect changes in the operation of the motor, which promises the need for an adjustment process. Even if you are not sure about the need for adjustment work, then their extraordinary performance will definitely not be superfluous.
Adjusting the carburetor on gas mowers and lawn mowers. setup instructions with step-by-step description
The process of adjusting the carburetor of the gas trimmer or trimmer is not difficult, however, its implementation should occur step by step in compliance with the recommendations. Before starting work, it is necessary to carry out preparatory actions, namely:
- Flushing the engine is advisable, but not necessary.
- Check the spark plug and, if necessary, clean it, measure the clearance and replace. Do not forget that candles have their own resource, and are consumables. Sometimes the unstable operation of the internal combustion engine may be connected precisely with the malfunctioning of the candle
- Check if 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 leakage or primer. After tightening and replacing the gasket, the carburetor may not even need to be adjusted
- Check the condition of the connecting adapter, which is between the carburetor and the CPG
- Clean or replace the air filter. It all depends on the state of the filter element. If the element is suitable for use, the filter can be washed in soapy water, then dried and continued to operate.
- Fasten the spool or cutting knives to the tool spindle. Adjustment is carried out under load, even if insignificant
When all the points of preparation are completed, we proceed to the direct process of tuning the carburetor. First you need to start the engine, and let it run for 5-10 minutes, depending on the ambient temperature. When starting the motor on the XX, the coil or knives on the trimmer should not rotate. If they move, then it is necessary to reduce idle speed. The photo below shows an example of the location of the adjusting screws that make the adjustment.
Using a slotted or Phillips screwdriver, we proceed to the direct process of tuning works. First, we reveal the number of screws for adjustment, since there can be 2 or 3, which depends on the manufacturer of the tool. Typically, Chinese trimmers are equipped with two screws. Below we consider the carburetor setup process, which has three tuning screws:
- A regulator labeled L. you need to start tuning manipulations with it. It is necessary to turn the screw while the motor is running. This screw is responsible for enriching the mixture at low speeds, so it should be screwed so that it reaches its maximum value. Usually this bolt rotates all the way, and then loosens by ¼ turn. If there are dips, it is necessary to tighten the bolt again to the stop, and loosen it by 1/8
- Screw marked T or LA. it is used to set the idle speed. The rotation of the bolt to the right side (twisting) contributes to an increase in idling, and to the left to decrease. When the revolutions of the twentieth increase, it means that more air is added to the combustible mixture. The mixture is leaner and its power or traction is lost. Reduced revolutions on the twentieth indicate an excess of air in the mixture, so you need to find a middle ground. The setting must be done so that the engine of the brushcutter works stably on the twentieth, and the reel with the fishing line or the steel cutting disc does not rotate. Rotation of the cutting elements contributes to quicker grip wear.
- Screw marked H. this screw is responsible for setting the combustible mixture at high speeds. It is with this screw that the tuning manipulations end. The maximum speed value is indicated in the technical description of the tool. To maximally accurately determine the value of the maximum speed, you should use the tachometer. If there is no tachometer, then tuning is done by ear. As soon as the maximum speed is reached by ear, the valve must be returned half a revolution back (counterclockwise). Bolt H is responsible for power, temperature and fuel consumption
Often, it is precisely with the setting of maximum revolutions that difficulties arise. To prevent this from happening, the following actions are performed:
- By pressing on the gas, it is necessary to rotate the screw until the speed decreases (clockwise or right)
- After reducing the speed, it is necessary to rotate the bolt so (counterclockwise or to the left) in order to detect unstable engine operation
- Once this unstable operation is detected, turn the screw clockwise until smooth operation of the engine
- This completes the adjustment process.
If the tuning 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. Setting up a carburetor with two screws is much simpler, but the tuning accuracy is much lower. Typically, Chinese gasoline tools, as well as household units, are equipped with 2 screws.
Summing up, it should be noted that you can not understand the principle of operation of the membrane carburetor benzokos and trimmers. It is important to have a screwdriver and a tachometer for tuning. However, in order not only to adjust, but also to understand what you are doing, you need to know the design and principle of operation.