No one operating a chain saw is really interested in any gradations between idle and full throttle, so incremental performance between these two extremes is not very important. In a car, the many gradations are important, and this is why a car's carb is a lot more complex. This short video 5. Watch the video for a better look at these parts. The carb is operating "normally" at full throttle.
In this case, the throttle plate is parallel to the length of the tube, allowing maximum air to flow through the carb. The air flow creates a nice vacuum in the venturi, and this vacuum draws in a metered amount of fuel through the jet. You can see a pair of screws on the top-right of the carb in photo 1. One of these screws labeled "Hi" on the case of the chain saw controls how much fuel flows into the venturi at full throttle.
When the engine is idling, the throttle plate is nearly closed the position of the throttle plate in the photos is the idle position. There is not really enough air flowing through the venturi to create a vacuum.
However, on the back side of the throttle plate there is a lot of vacuum because the throttle plate is restricting the airflow. If a tiny hole is drilled into the side of the carb's tube, fuel can be drawn into the tube by the throttle vacuum.
This tiny hole is called the idle jet. The other screw of the pair seen in photo 1 is labeled "Lo" and controls the amount of fuel that flows through the idle jet.
When the engine is cold and you try to start it with the pull-cord, the engine is running at an extremely low rpm. It is also cold, so it needs a very rich mixture to start. This is where the choke plate comes in. When activated, the choke plate completely covers the venturi watch this video of the choke plate to see it in action. If the throttle is wide open and the venturi is covered, the engine's vacuum draws a lot of fuel through the main jet and the idle jet.
Usually, this very rich mixture will allow the engine to fire once or twice, or to run very slowly. If you then open the choke plate, the engine will start running normally. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. To increase the speed, they should be turned clockwise.
In order to reduce the speed, the screws turn against it. To adjust the carburetor, you will need a special screwdriver for adjustment. The carburetor adjustment process consists of two stages: initial and main. The algorithm of actions during adjustment is as follows:.
Do not rush when adjusting the chainsaw. It must be remembered that the slower you turn the screws, the better you will feel the changes in the operation of the tool engine. After adjustment, you need to check the acceleration, the maximum number of revolutions and the engine idling. In the process of checking the first parameter, sharply press the trigger of the gas.
To measure the maximum speed you will need to use the screw "H". In order to increase the maximum speed, the screw rotates clockwise. To reduce the rate, the screw must be turned in the opposite direction.
It should be remembered that the maximum number of revolutions should not exceed 15 thousand. For the final check of the chainsaw when idling, you need to start the tool and put it on a level place. Let the engine warm up and pay attention to the following elements of the chainsaw:. An important tip is that if the carburetor is set up correctly, then the sound of the chainsaw motor will strongly resemble the sound when the 4-stroke engine is running.
In a similar manner, the carburetor of the Chinese chainsaw is adjusted and checked. The only difference is that the process of setting up such tools can take much more time. In addition, it should be remembered that the adjustment of Chinese chainsaws is required much more often. Before cleaning the carburetor or performing its repair, this element of the chainsaw will need to be removed and disconnected from other nodes. To do this, you must follow a certain procedure.
The dismantling algorithm is as follows:. Try to perform each of the actions as carefully as possible. Otherwise, there is a risk of damage to important elements of the chainsaw. It is necessary to flush the chainsaw carburetor in cases where low-quality fuel is used to refuel the tool or the tool is used at extremely low temperatures.
In the process, you must try not to damage or lose small parts of the assembly. The carburetor is cleaned in the following order:. After cleaning the carburetor with your own hands, you will notice that the chainsaw motor will work much more stable and gain more speed.
The principle of operation of the engine used in a modern chainsaw involves the combustion of a pre-prepared fuel formation, consisting of a mixture of air, oil and gasoline. In order for the mixture to enter the combustion chamber in a predetermined proportion, the device needs a special mechanism called a carburetor. Adjusting the carburetor of the chainsaw ensures the optimal composition of the combustible mixture and the required power transmitted from the working shaft to the cutting blade.
Regardless of the manufacturer of a product, the essence of the work and the device of any gasoline carburetor remains the same. To obtain a high-quality mixture of air and gasoline, it must include the following mandatory units:. During the operation of the device, air entering under atmospheric pressure through a special filter is fed into the narrowing zone of the carburetor, in which its flow rate is controlled by a movable damper that blocks the inlet section of the tube.
At the exit of the narrowing part of the tube due to the expansion of its diameter, a vacuum zone is formed, into which fuel is automatically sucked from the fuel supply channel. The intensity of this process is regulated by a special metering needle connected by means of a jet to the float chamber. The following characteristic signs testify to the abnormality of the operation of a manual chainsaw:.
The detection of at least one of these signs is regarded by many as a deviation from the norm and forces the user to take timely measures to eliminate the problems that have arisen. Correctly adjust the chainsaw. Violation of the functioning of at least one of the nodes is a signal to the need for timely adjustment of its operating mode.
When determining the characteristic signs and causes of a malfunction of the carburetor device, the following should be considered. Firstly, a decrease in engine speed and loss of power can occur due to a change in the air-gasoline ratio in the mixture its depletion is due to a large amount of oxygen. With excess fuel, there is also a violation of the operating mode, manifested in a decrease in power, which is explained by incomplete combustion of gasoline vapors.
In the second case, incomplete combustion of the fuel is observed with the simultaneous formation of a carbon layer in the cylinders and the appearance of a characteristic black exhaust mixture is oversaturated.
All these deviations indicate either a malfunction in the air supply channel or a clogged carburetor nozzle. Secondly, the lack of stability of idling indicates that the fine tuning of the mixture supply to the combustion chamber is violated, which can be caused by the same reasons. If these malfunctions are detected, a complete cleaning of the carburetor will be required, including a mixture dosing device easier.
When purchasing a new chainsaw, it is usually already adjusted to the composition of the mixture recommended for use specifically for this model. To adjust adjust the carburetor in this case, it is not necessary to remove and disassemble it. It is possible to solve the problem by carrying out fine adjustment operations carried out by means of the three screws available on the case.
One of them with the code T is intended for dosing the fuel supply in idle mode. The second screw under the designation H ensures the operation of the chainsaw at maximum loads, and the third. L ensures its stable operation at low speeds. Since the adjustment of the carburetor device is carried out only by ear that is, it is mandatory when the engine is running , special attention should be paid to the safety of the check.
To do this, the saw must be firmly fixed on a level base, and its cutting part is directed in the direction opposite to the inspector. Before starting the adjustment operations, the initial position of all three screws must be marked with the help of an improvised painting composition or felt-tip pen. For the final fine tuning of one or another model of the chainsaw carburetor, it is more convenient to use the instructions for its operation. To remove the carburetor from the chainsaw, it is necessary to unscrew the fixing bolts and disconnect all the supply pipes.
But first, you need to free the assembly from the fasteners in the place of fixation on the saw body, first cleaning their surfaces from dust and dirt. First of all, the saw is freed from the air intake, after which free access to the carburetor and the suction rod located next to it will open. After this, the accelerator lever should be removed, for which the carburetor damper first lowers. Immediately after this, it will be possible to completely release the carburetor by removing another lever suction.
The latter is removed after raising a suitable wire to it, carefully picking it up from the left side. Completely freed from all bonds, the carburetor is thoroughly washed in gasoline and blown with compressed air. Upon completion of removal of the device from the saw, it will be necessary to clean its grate by injection, for which you can use a thin needle of a suitable size.
Before you start disassembling the carburetor yourself, first of all, you need to prepare a flat area and spread a piece of clean matter on it. In addition, you will need such an auxiliary tool as a soft-brushed brush, a Phillips screwdriver, a socket wrench or a head with size M6.
To clean and rinse the parts removed from the chainsaw, it is necessary to prepare a little clean gasoline, poured into a container convenient for drawing on them.
After disassembling the carburetor, the user will find a set of parts. All of them are laid out on the canvas in the sequence corresponding to the order of their subsequent washing. The assembly of the carburetor of the chainsaw after cleaning and washing is carried out in the reverse order with strict observance of all the subtleties of its device.
Upon completion of the assembly procedures and after the installation of the device in its place, you should again make adjustments according to the previously described methodology. Hand-held gasoline tools have firmly entered our household life.
Now every owner of a country house or cottage has a manual gasoline saw. For a person far from technology, adjusting a chainsaw seems a very difficult task. In this article we will look at the device of a gasoline engine and show how to adjust the carburetor on a chainsaw. The principle of operation of a gasoline engine is to burn a compressed mixture of air and gasoline in a combustion chamber. The main elements of any internal combustion engine in short. ICE : a cylinder in which the piston moves up and down under the pressure of the combustion products of the fuel mixture, and a crank mechanism that converts the reciprocating motion of the piston into rotational motion of the crankshaft.
In the intake stroke, the piston moves down, creating a vacuum in the cylinder, and, like a pump, sucks in the fuel mixture. When the piston reaches a high point, the mixture is compressed as much as possible. At this moment, it is ignited by an electric spark. The compressed mixture burns out very quickly, almost instantly. Something similar to a fuel mixture explosion occurs. This explosion pushes the piston down, the engine begins to move.
During the stroke, the piston moves from the top to the bottom, pushing the crankshaft and doing useful work. In the exhaust stroke, the piston moves upward, pushing the exhaust products of combustion into the atmosphere from the cylinder. There is an exhaust. The most obvious principle of the internal combustion engine is implemented in a four-stroke engine. In this type, a full cycle of work occurs in two crankshaft turns. The first revolution is inlet and compression.
The second turn is the working stroke and release. Accordingly, there are two valves. Opening and closing valves is synchronized with the position of the crankshaft. To do this, use the gas distribution system. If you combine two cycles, we get a two-stroke engine. In it, a complete duty cycle occurs in one revolution of the shaft. In this type of engine, there is no need for valves and, accordingly, in a complex and heavy gas distribution system. The intake and exhaust valves replace the slots in the cylinder.
The two-stroke engine can be made extremely simple, lightweight and at the same time quite powerful. Each type of engine has its advantages and disadvantages. To date, all automotive engines are four-stroke. Two-stroke engines were previously installed on some old cars, but this is the heritage of automotive antiquity. All manual gasoline tools are usually push-pull.
True, recently chainsaws and lawn mowers with four-stroke engines have appeared on the market, but this is still exotic, and their advantages in this segment are not obvious. In the combustion chamber of the internal combustion engine, not gasoline is burned, but a mixture of gasoline with air.
To achieve high engine speeds, it is necessary that the mixture burns as quickly as possible, practically explodes. Gasoline itself burns slowly. And gasoline vapors explode from the slightest spark. That is why it is dangerous to be near puddles with spilled gasoline.
Therefore, it is necessary to store gasoline in sealed containers. For the same reason, it is impossible to kindle the stove with gasoline and pour gasoline into plastic containers, in which sparks from electrostatic discharge are possible.
To prepare a mixture of gasoline with air and control the flow of this mixture into the combustion chamber, a carburetor is used. In modern cars, the carburetor has been replaced by a more complex and advanced electronically controlled direct injection system. Even a blonde knows how a spray gun works. We press on a rubber bulb and air pressure is supplied to the atomizer. The atomizer is connected by a thin tube to a bubble into which liquid is poured. The air in the atomizer carries liquid from the bubble along, and we get a mixture of liquid and air at the outlet.
The amount of air supplied is regulated by a throttle. By pressing on the gas handle, we open the shutter, and when released, the return spring returns the shutter to its original position.
This changes the engine speed. In order for the engine to work stably, it is necessary to maintain a certain ratio of gasoline and air in the fuel mixture. If there is little gas, the mixture will be lean and the engine will not reach the required power.
If there is too much gas, then the mixture will be too enriched, which is also bad. To adjust the ratio of air and gasoline is a jet. The jet is the very tube in the atomizer bubble.
Only very thin. In addition, the cross section is regulated by a conical needle that overlaps the hole. By turning the needle inward, we reduce the section of the hole and, accordingly, the supply of gasoline to the mixture, while twisting it, we increase it. The air-gas ratio is different for low and high revs, so most carburetors have two jets and two adjusting screws for low and high revs.
The low-speed screw is usually marked with the letter L, from English Low. The high-speed propeller is indicated by the Latin letter H, from English High. The flow of the mixture is controlled by a throttle.
The more the shutter is open, the higher the speed. At idle, the shutter is almost closed. If the shutter is completely closed, the engine will stall. The opening angle of the damper at idle is controlled by a special screw, usually indicated by the Latin letter T, from the English Throttle.
Different manufacturers may have different designations, so read the instructions. Here we will show you step by step how to adjust the chainsaw carburetor. As a rule, during normal operation, a full carburetor adjustment is not necessary. Sometimes it may be necessary to adjust screw T for stable idle operation.
By turning the screw clockwise, we increase the speed, while turning it counter-clockwise, we decrease. It is necessary to achieve stable operation of the engine, but so that at idle the centrifugal clutch does not work, that is, the chain remains stationary. If, however, full adjustment is necessary, then proceed as follows: with the engine turned off, we turn both screws L and H clockwise to the stop. Then we turn one and a half turns to the left. This is the standard position. Then we launch the saw and check how it reacts to the addition of gas.
If the reaction is sluggish. Screw N sets the maximum engine speed. They are usually indicated in the instructions. For adjustment it is necessary to have a speed meter.
There are methods for adjusting speed without a tachometer by ear. We do not exclude this method, but also do not recommend it. If these adjustments do not give a result, we are looking for a reason. Chainsaw requires clean air. The smallest speck of dust that gets into the nozzle will disrupt the carburetor. Therefore, it is necessary to clean the air filter in time. The same applies to the fuel filter.
The two-stroke chainsaw engine does not have a lubrication system. Instead, oil is added directly to gasoline. The normal proportion of oil in the fuel mixture is 2 percent. That is, the ratio of oil to gasoline is 1 to 50 by volume. Prepare the fuel mixture correctly.
Oil is poorly soluble in gasoline. Therefore, you need to thoroughly shake the mixture during cooking and before pouring it into the gas tank. Use the mixture on time, do not store it for future use. For the same reason, it is not recommended to leave the mixture for a long time in a non-working carburetor.
Before leaving the saw for a long time, it is necessary to drain the remainder of the mixture from the gas tank and let the saw idle until it stops to work out the remaining fuel in the carburetor float chamber. Check the condition of the spark plug by turning it out of the socket. The candle should be dry and clean, light brown in color.
If the candle is wet and black, this may indicate an excess of oil in the mixture and whether the fuel is incompletely burned. Rinse the candle with clean gasoline and dry thoroughly. In no case do not light a candle, as is sometimes advised. If the porcelain insulator cracked, replace the spark plug. Often the cause of poor performance is clogged muffler.
And not the silencer itself, but the spark-extinguishing grid, which is installed at its outlet to protect against sparks.
Due to soot, small mesh cells become clogged and the saw loses power. Rinse the net at least once a season. Some wizards recommend completely removing this grid. But since the net is a protective measure against accidental ignition of flammable objects, such as dry grass, that are near the saw, we do not support this recommendation.
Sometimes the cause of unstable operation is the suction of extraneous air. Check carburetor and muffler mounting. They are fastened with long bolts through gaskets. It is believed that the complete disassembly, repair and assembly of the carburetor is a difficult task and you need to contact the service.
However, the service is not always nearby, and it is quite possible to repair the carburetor yourself. The chainsaw carburetor is pretty simple. If there is not enough fuel, or it mixes poorly with air, the engine starts to intermittently or does not work at all.
For this reason, it can also be damaged in a two-stroke engine, the fuel also supplies engine lubrication. If too much fuel is mixed with air, the engine runs excessively hard, with a lot of smoke, intermittently. The carburetor is an important component responsible for the correct mixture and condition of the engine.
The chain saw operators are not interested in the specifics of the carburetor in the intermediate stages. The carburetor is essentially a pipe. The principle of operation of the carburetor chainsaw has features. On the tube, called the throttle plate, there is an adjustable part that controls how much air can pass through the tube.
You can see this round brass plate when disassembling the carburetor. In some part, the tube narrows. This part is called Venturi, it is responsible for the vacuum. There is a hole in this part of the carburetor that allows the vacuum to trap the fuel. The carburetor will work correctly at a normal pace with full throttle. Then the plate will be located parallel to the tube, which will allow enough air to get into the carburetor.
When analyzing a chainsaw, you can see several screws in the right corner of the carburetor, on top. One of the screws will control how much fuel flows into the venturi. When the chainsaw starts to idle, the shutter will be half closed. The movement of air through the venturi does not create enough vacuum. But there is a lot of vacuum in the back of the throttle plate the damper restricts air movement.
When the engine is cold and the operator tries to start it with the cord, the engine will start to operate at extremely low speed. To start the engine requires a fuel-air mixture. The throttle plate closes the venturi, which means that the vacuum in the engine draws in a lot of fuel. This usually allows the engine to operate quickly, but run slowly.
If the operator then opens the throttle, the engine will start to run normally. With sparks, fuel, air compression, the problem with poor engine performance, most likely, is the problem with the carburetor.
Inspect the fuel pipe. A common problem is often a cracked fuel pipe. This will cause a fuel supply problem, which is an important factor for carburetor operation.
Removing the fuel pipe is quite simple. As before, you will need to remove the fuel filter. Then pull out the fuel pipe, dry it, bend it in several different directions, trying to see signs of wear.
Replace handset if there is any problem. Stihl chainsaw carburetor operation can be unstable, as is the case with any other chainsaw, if the problem is a clogged carburetor. The operator has 2 options. You can purchase a recovery kit on the Internet, clean the carburetor well, return it together and hope that the problem is fixed. You can easily purchase and install a new carburetor.
Chinese carburetors are cheaper. Most push-pull carburetors are the same, so sometimes buying an affordable option can be a good solution. But for expensive chainsaw models, you should choose the original carburetors for replacement.
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