Stihl chainsaw carburetors have a story. In 1958, Stihl for the first time in the world developed a membrane-type Flieger carburetor, with which the chainsaw can work in any, even upside down. Over time, only such carburetors began to be used on all chainsaws in the world.
Which carburetor is installed on a Stihl MS 361 chainsaw
The Stihl MS 361 chainsaw is equipped with a modern C3R. S 236 diaphragm carburetor with an integrated fuel pump. Manufacturer. Stihl. When assembling its chainsaws, Stihl does not use components from other manufacturers, for example, Walbro, as many companies of other brands do. Carburetor Stihl MS 361 is well thought out constructively, economical, provides stable engine operation at any speed.
Device and principle of operation
The Stihl MS 361 chainsaw carburetor consists of 42 parts, including gaskets and mounting screws. Main nodes:
- case with air and fuel supply channels, storage chamber;
- air and throttle valves;
- manual fuel pump (primer).
Fuel from the gas tank enters the carburetor, is sprayed there, mixed with air, the formed fuel-air mixture is fed into the combustion chamber. A mixture with a high content of gasoline is called enriched. If there is more air and less air, the mixture becomes lean. The composition of the mixture is adjusted with adjusting screws. The carburetor is considered a complex device, because it provides the internal combustion engine in three different modes. cold start, idle and at maximum speed.
During a cold start, gasoline is pumped up with a pump (primer button). At this point, an enriched mixture with a large amount of gasoline enters the still dry combustion chamber, which facilitates starting. At start, the choke is closed.
After starting in the combustion chamber during the operation of the internal combustion engine, a vacuum is formed in which the fuel-air mixture is sucked in automatically.
At idle, the throttle is closed, the flow of the mixture is limited.
When you press the throttle, the throttle opens slightly, increasing the flow of the mixture and the speed of the engine.
The function of the membrane is to shut off the fuel supply to the storage tank from the gas tank when it is full, and to open when the fuel becomes low.
Accumulative capacity is sometimes called a “float chamber” by habit, although there is no float in membrane carburetors.
In the “throttle to full” position, the throttle and air damper are fully open. The flow of gas in this mode is regulated only by a calibrated hole in the high-speed jet. The adjusting screw H during adjustment can reduce or increase the flow of gasoline through this hole. Screws L and LA regulate single and small turns.
Appearance of the carburetor chainsaw Stihl МС 361
Do-it-yourself carburetor adjustment for the Stihl MS 361 chainsaw
Three adjusting screws are mainly for factory adjustment. After assembling the carburettor and saw, each of them is adjusted one at a time, on special stands, taking into account the characteristics of each Stihl MS 361. chainsaw. The screws are securely locked and do not loosen spontaneously during operation. Adjustment is rarely required. Namely:
- During critical wear of the piston system, when the compression ratio (compression) has changed significantly.
- When replacing the piston system when the chainsaw does not work as it did during the factory setting.
- When working in the mountains, where, due to low atmospheric pressure, the engine does not have enough oxygen, it is necessary to increase the air supply (lean mixture).
In other cases, most often, idle speed adjustment is required if the engine stalls in this mode.
A feature of the Stihl MS 361 chainsaw is easy access to the carburetor. It is enough to remove the cover and air cleaner. Therefore, no tool is needed for adjustment except a screwdriver. For professional adjustment, a tachometer is required. It will show the number of idle and maximum revolutions. Proper adjustment should provide 2500 rpm at idle and 10,000 rpm at maximum speed.
The Stihl MS 361 chainsaw can develop 12,500 rpm, but it is not recommended to operate it in this extreme mode.
In the absence of a tachometer, maximum revolutions are determined by ear. Single. in two boundaries: the chainsaw should not stall when idle is low, the chain should not move when speed is too high.
The tachometer allows you to more accurately adjust the maximum and minimum revolutions of the chainsaw
Step-by-step adjustment algorithm
Before adjusting, make sure that the air filter is clean. If it is clogged, there may not be enough air to completely burn the fuel mixture. Therefore, the engine does not work correctly. Perhaps adjustment is not required, but you need to clean or change the filter.
The filter is removed and they try how the engine works without it. If good, then the problem is in the filter.
An engine without an air filter cannot work for a long time, only a test run. Debris trapped inside the engine could damage it.
The presence of soot in the spark arrester grille and silencer is also checked. If the exhaust outlet is difficult, the engine also does not work correctly and the problem is not in the carburetor setting.
The chainsaw manufacturer Stihl MS 361 in the Operating Instructions (p. 37) recommends the following carburetor adjustment algorithm:
- Turn the high-speed adjusting screw H clockwise until it stops, but not more than 3/4 turn.
- Screw the idle adjustment bolt L clockwise until it stops. Then turn counterclockwise 1/4 turn.
- Start and warm up the engine for 7-10 minutes.
- Further idle speed is adjusted by adjusting the thrust screw LA with the engine running. It is screwed in clockwise, increasing idle speed until the chain starts to move. Then, the LA screw is turned back 1/2 turn.
- If during adjustment with the LA screw it is not possible to correctly adjust the idle speed (the engine stalls or the chain rotates), they are adjusted with the L. screw. It is unscrewed by 1/4 turn. Then continue to adjust the screw LA, unscrewing it counterclockwise until the chain stops. Then in the same direction another 1/2 turn. But so that the engine does not stall at idle.
In addition to the manufacturer’s recommendations, there are practical points for adjusting the carburetor.
Stihl MC 361 chainsaw carburetor adjusting screws
Nuances to Know
When turning any screw, the factory setting changes. Therefore, it is extremely important to remember or record the number of revolutions by which the position of the screws has changed during adjustment. For example, if the screw is fully tightened, it must be tightened, always counting the revolutions. Only this will make it possible to return to the factory settings if it proves unsuccessful.
Adjustment is carried out only on a warm engine, otherwise it will turn out to be incorrect. a cold and a warm engine work differently.
Adjustment of high speeds is easiest to carry out with the engine running. Screw N is turned in small steps 1/4. 1/2 turn in one direction or another. By pressing the throttle stick, they try how the engine reacts to a change in setting. Changes in revolutions are determined by ear or by tachometer.
After adjusting high revs, it is often necessary to adjust the idle speed adjustment.
The author of the video shows an example of the original Chinese-made carburetors that are used on the Stihl MS 361. Zam chainsaw. Carries out its comparison with the German Walbro carburetor. Also gives an example of a fake carburetor. The video is very useful, it is recommended for viewing by both beginners and experienced. We thought the problem was in the carburetor, but it turned out he was completely out of business here, everything was much more serious.
Advantages and disadvantages
The original Stihl chainsaw carburetors have no technical flaws. This product is from German manufacturers, technically thought out and modern. The cross-sections of the channels and the throughput of the calibrated holes are precisely calculated.
Walbro carburetor used on Stihl MS 361 chainsaws
An engine with such a carburetor does not consume excess fuel, but is capable of operating at full power. Suitable materials are used for its manufacture. The metal is not oxidized, it is strong enough. Plastic parts are not corroded by gasoline and last long enough.
Problems arise mainly with counterfeit carburetors from unknown manufacturers.
The original Stihl chainsaw carburetors do not break even because the carburetors on any chainsaws do not experience large mechanical and temperature loads. Failure in the original carburetor of the Stihl MS 361 chainsaw can only gaskets and a membrane. After many years of use, plastic can change its properties, become hard or brittle. In this case, you can purchase a repair kit and replace old parts.
It is extremely rare to buy a new carburetor assembly, only in exceptional cases.
But no manufacturer can give a 100% guarantee of eternal work for their products.
Sometimes carburetors from Stihl MS 361 chainsaws are bought in order to install them on chainsaws of other brands of similar power.
How much does a carburetor cost for a Stihl MS 361 chainsaw
Today, there are at least four types of carburetors for the Stihl MS 361 chainsaw on sale.
They cost from 1600 to 6400 rubles. At foreign sites. about 41 dollars.
The huge price range suggests that some of them are non-original, counterfeit and low-quality carburetors.
Stihl chainsaws are famous for their reliability, so the need for adjusting the carburetor and its repair is very rare, if such a need still arises, it is better to entrust the tuning process to specialists in their field, if only because you need to have a tachometer to set the maximum speed.
If you have an urgent need to set up a carburetor on a Stihl MS 361 chainsaw, then strictly follow the algorithm and recommendations described in the article. And then, if possible, contact a specialized center as soon as possible for fine tuning, it will extend the life of the chainsaw.
Stable stable operation at any speed, developed power, efficiency, the use of technical capabilities in the amount provided and laid down by the manufacturer, and even the motorcycle saw’s engine life. it all depends on its carburetor. In addition to the fact that this node must also be maintained and maintained in a timely manner, it must also be properly adjusted. Setting up a chainsaw carburetor is not an easy task, but with a leisurely thoughtful approach and strict adherence to instructions, practically anyone is feasible, and it should be carried out at the first signs of need for it, moreover, regardless of whether the new chainsaw is in operation or has been seen.
The following reasons, signs and malfunctions testify to the need to adjust the fuel supply unit (hereinafter the UPT, i.e. the carburetor)
- factory or own settings were lost due to loosening of adjusting bolts and vibration, or during unsuccessful attempts to adjust the carburetor to a new one;
- damage to the housing cover;
- the engine does not start or starts with a strain, and then stalls almost immediately;
- the saw does not work stably at idle or does not hold them at all;
- excessive fuel consumption and too thick exhaust;
- electrodes of spark plugs are black (supply to the motor of a re-enriched mixture) or with a white coating (depleted);
- the chainsaw does not develop maximum speed or power;
- the motor stalls during a set of turns;
- there is a strong vibration of the chainsaw;
- due to disturbances in the operation of the air cleaning system, particles of debris get into the mechanism distributing the air-fuel mixture;
- the piston group has significant wear and tear. in this case, the regulation of UPT is used as a temporary measure to make the tool more stable.
Naturally, the fuel system must be flushed out if dirt enters it. adjusting the carburetor cannot solve this problem. A worn piston needs major repairs. However, in these cases, too, perform the setup.
Chainsaw carburetor adjustment
It may also be necessary to adjust the temperature control even when changing the brand or quality of fuel, atmospheric pressure, humidity and ambient temperature, altitude (when the place of operation changes from a plain to a mountainous area, it is due to rarefaction of air, and vice versa).
Before adjusting the UPT, you must make sure that both filters (air and fuel) are clean. In addition, there should be no air leakage into the motor from the side (through the seals, the gasket under the UPT or its accelerator pump, or elsewhere), otherwise it will not be possible to adjust the carburetor.
Video: How Stihl 360 And 361 Saws Differ
Preparing for carb adjustment
Almost any UPT is regulated by 3 screws:
- 1. The bolt of the main nozzle, designated “H” and used to set the maximum revolutions of the saw motor.
- 2. Idle jet bolt, designated “L”, used to set low revs. That is, for idle control.
- 3. The idle adjustment bolt, designated differently by different manufacturers: “S”, “LA” (Stihl), "T" (Partner, Husqvarna)
Carburetors with fewer adjusting screws are also found. So manufacturers protect their products from unprofessional interference and at the same time try to simplify their setup.
Before starting the adjustment, you should carefully study the operating instructions supplied with the chainsaw, especially the part where the rotation angles of the adjusting bolts are given. This is an important condition that will allow you to configure without going beyond the operating parameters of the engine, correctly.
For safe regulation during its implementation should observe the rules:
- 1. The tool must be stably installed on a flat surface of a rigidly fixed object (workbench, rack, table).
- 2. The chain should be directed away from itself and others present.
- 3. There must be a safe distance between the chain and any surrounding objects, guaranteeing the impossibility of their mutual contact.
In such cases, adjust the carburetor on the chainsaw as follows. First, start the tool and warm it up for 10 minutes.
We begin the adjustment of the UTP by determining the position of the tuning screw “L”, at which the idle speed will be the highest. To do this, very slowly and smoothly turn this bolt one way, then the other. And so several times until the desired position is found. After that, we turn “L” 1 / 8–1 / 4 turns (the required value is indicated in the technical documentation for the tool) counterclockwise (hereinafter referred to as the PSD).
Then we continue to idle control using the screw “S” (“LA”, “T”):
- If, after manipulating the bolt “L”, the chain is stationary, then it is necessary to smoothly rotate “S” (“LA”, “T”) clockwise (hereinafter referred to as PSR) until it starts to move. Then we twist “S” 1 / 8–1 / 4 turns back.
- If the chain moves, rotate the “S” (“LA”, “T”) of the EMR until it stops, and then twist the “S” 1 / 8–1 / 4 turns in the same direction.
The engine should run evenly. And check it, how it accelerates. It is believed that the motor in acceleration mode works fine if, when you press the accelerator gently, the speed in a short time and without “dips” increases to its maximum value. If the engine does not work uniformly and / or accelerates poorly, then slightly. at a maximum of 1/8 of a whole revolution. it is necessary to twist the "L" frequency converter. After this, it is necessary to make the above setting “S” again (“LA”, “T”). We repeat these adjustments until the motor starts to work evenly and accelerate well.
Checking the operation of the chainsaw
Now we check the adjustment of the adjusting bolt “H”. To do this, we accelerate the engine to maximum speed. Only for a long time it is impossible to drive it without load, you need to pause. We look at the exhaust and listen to the engine. If too much smoke comes out of the muffler, with bluish smoke, and the chainsaw makes a lot of noise, then the carburetor makes an excessively rich mixture. In addition, while the maximum speed of the power unit is lower than it should be. And also it will form a deposit. In this case, you need to “H” a little twist POPS. Then we again check the operation of the engine and, if necessary, repeat the adjustment.
When the chainsaw makes a screeching sound, the engine is very hot, the exhaust is accompanied by a crash and / or interruptions in the ignition are heard, that is, detonation occurs. the mixture is too lean, and the maximum engine speed is higher than it should be. This leads to overheating of the power unit, burnout of the piston, rapid wear of the cylinder and burnout of the plug. In this case, it is necessary to “H” turn 1/4 of the turn of the PSD.
At the end of the adjustment, we check the saw at idle. With a properly adjusted UPT, it should work like this:
- 1. The chain is stationary.
- 2. The sound of the engine is almost like a four-stroke.
- 3. Pressing the accelerator leads to a quick set of maximum speeds.
If these conditions are not fully complied with, use “S” (“LA”, “T”), as indicated above, or repeat the setting from the very beginning.
This is an approximate setting. For accurate, you need a tachometer. We do the same thing, just turn the adjusting bolts, focusing on the readings of this device. This will allow you to accurately and, most likely, adjust the carburetor the first time, depending on the model of the tool for working with the tree, set the idle speed at the level of 2800–3300 rpm or higher and the maximum. 11000-15000 rpm. Which ones should be set should be looked at in the technical documentation (operating instructions) for the saw.
After maintenance, such as disassembling and flushing, or previous unsuccessful attempts to set up this unit, it may turn out to be completely deregulated. So much so that the chainsaw will not start at all. In this case, it is necessary to configure the device of the engine power system in 2 stages, conditionally called:
- basic. with the engine idle;
- final. produced on a warm engine.
At the first stage, the adjusting screws “L” and “H” are slowly screwed in with the POPS until the stop. In this case, it is not necessary to make great efforts and try to tighten them. Then we turn both screws back. for many models I drank 1 revolution. And for some. by 1.5 turns. There may be other settings. This should be clarified in the technical documentation for the chainsaw. For some models, a hint is applied directly to the cover of their case near the adjusting screws.
This will carry out the recommended factory default carb setting. In this case, the screw "S" ("LA", "T") in no case do not touch, unless of course it has not been twisted. When he is already twisted, you have to work with him. Slowly screw in the “S” SPSF as far as it will go.
We pass to the final stage. We are trying to start the engine. If there were no manipulations with the “S” adjustment (“LA”, “T”) and exactly as recommended “L” and “H” are set, then it should start.
If the “S” had to be tightened for the reasons stated above, then the engine most likely will not start immediately. It will be necessary after each attempt to tighten this screw 1/4 turn POPS and again try to start the engine. In the end, he must earn.
Then warm up the engine for 10 minutes. If, after starting it up or during warming up, the motor is unstable or the chain starts to move, then slowly and carefully rotate the “S” (“LA”, “T”) of the frequency converter. As soon as the engine starts to work stably and / or the circuit stops, we immediately stop the adjustment. If the motor stalls, then turn this screw 1 / 8–1 / 4 (see technical documentation) of the RPM.
In the process of warming up, the idle speed can begin to increase, then, again, it will be necessary to “S” (“LA”, “T”) begin to slowly twist the PSD, until they become normal by ear. With the engine already warmed up, we continue to adjust the power supply unit, as described in the previous chapter.
After running on the saws, only fine tuning of the UPT is performed. For this, a tachometer and technical documentation for the used sawing tool will be required. The fact is that the factory manufacturer has already set almost optimal settings. Just to break in the engine and grind other moving parts of the chainsaw, the carburetor is configured to prepare a slightly more enriched than the calculated optimal, air-fuel mixture. Due to this, the maximum speed is slightly lower than the design level laid down by the manufacturer and plus the motor is better lubricated. Due to this, engine break-in and running-in of the remaining moving parts take place sparingly.
Therefore, if there is no tachometer and / or reliable information (passport data) about the maximum speed and idle, then it is not worth changing the factory settings after the break-in, since this will not work correctly. And in general, it is not necessary to perform fine adjustment in this case. the chainsaw will work perfectly on the existing basic settings. And if you do it, it is better in the service center. Jewelry tuning of the carburetor of a completely new tool is recommended to be entrusted to specialists.
Before fine-tuning yourself, it is strongly recommended that you note the position of the tuning bolts as accurately as possible. This will allow in the event of an unsuccessful attempt to return them to their place. to the basic factory settings. We begin regulation with a bolt "H". After setting the maximum speed, check idle. If they are different from normal, set them first with “L”, and then with “S” (“LA”, “T”). In doing so, we are guided by the rules and principles set forth in the second chapter of this article. But we turn the adjusting bolts, focusing on the tachometer readings. Then we continue to adjust the carburetor, as indicated in the same chapter. We turn the screws, watching the tachometer readings.
Chainsaw carburetor adjustment Stihl 180, 170 and other low-power produced only one screw. "LD". They set the idle speed.
The basic standard setting is as follows:
- 1. Completely twist the “LD” of the EMPS until it fits snugly.
- 2. Then we turn it back POPS 2 turns.
If you need to make additional or other adjustments, then first you need to warm up the motor for 10 minutes. Then, if:
- idle speed is too low. turn “LD” POPS until the chain starts to move, after which we turn this bolt 1/2 turn back, SRPS;
- the chain of the tool moves at idle. slowly turn the “LD” SPSF until it stops, after which we turn this bolt another 1/2 turn in the same direction.
And it’s better to tune with a tachometer, not forgetting that the chain should not move at idle. Maximum revolutions without load models Stihl 180 and 170. 13500 rpm. Single. 2800 rpm.
Adjust carburetor chainsaw Stihl, equipped with a more powerful engine, is produced in the same way as described in previous chapters. This applies to such most popular models as Stihl 210, 230 and 250. For the basic setting (discussed in the third chapter), “L” and “H”, after twisting, are turned back 1 turn. There are also saws with a carburetor, in which the basic setting "H" is 3/4 turn. By the way, this information is indicated on the cover of the tool body.
The angle (step) of rotation of the adjustment bolts during the adjustment of the UPT is 1/4 of a turn. Single revs of models Stihl 210, 230 and 250. 2800 rpm, maximum without load. 13000 rpm.
Owning a chainsaw in many ways makes life easier even for an amateur, and in some professions this tool is practically indispensable. However, like any relatively complex device, a chainsaw requires periodic maintenance. Due to untimely or poor quality maintenance, as well as the result of both planned and excessive loads, various kinds of malfunctions can occur. For professionals, interruptions or unstable operation of the saw reduce the efficiency of work or can cause a spoiled working day. One of the most common malfunctions is the incorrect setting of the carburetor of the chainsaw, which fails due to unsuccessful attempts to adjust or shift the adjusting screws for other reasons.
Symptoms of malfunctions and breakdowns that require carburetor tuning.
The following symptoms and malfunctions indicate the need for carburetor adjustment:
- the engine starts with a strain and stalls almost instantly;
- gas consumption is excessively large, the exhaust is too thick, the combustible mixture in the cylinder does not completely burn;
- the factory settings of the carburetor of the chainsaw are knocked down (due to vibrations or unsuccessful attempts at regulation);
- malfunctions of the air cleaning system, leading to the ingress of particles of debris into the mechanism distributing the fuel mixture;
- significant wear of the piston group. the carburetor setting in this case acts as a temporary measure.
It is clear that if dirt enters the fuel system with one setting, the problem cannot be solved. it needs to be flushed. In the case of worn piston overhaul is required. However, in all these cases, carburetor tuning is also performed.
Purpose, design and principle of operation of the carburetor.
A carburetor is needed to prepare the air-fuel mixture to power the engine. If the proportions in this mixture are incorrect, the motor is disrupted. If the proportion is not observed in the direction of increasing the amount of fuel, the mixture is called oversaturated, but if the fuel, on the contrary, is small. poor. Both the one and the other affect the engine’s operation not in the best way.
In different models of chainsaws, carburetors differ in design, but according to the principle of action, they are similar. A stream of air moves through the air channel at high speed. The damper blocking the channel allows you to change the speed of the air stream. Fuel through the sprayer is fed into the channel, where it mixes with the incoming air, forming a fuel-air mixture. The resulting mixture enters the engine.
The pressure in the float chamber, where the fuel is located before mixing, is almost equal to atmospheric. But a vacuum is created in the air channel, due to which the fuel is drawn into the air stream. The more the flap opens, the faster the air moves, and the amount of fuel also increases. the engine speed rises. So simplified, you can imagine the principle of the carburetor.
For efficient, smooth operation of the tool, obtaining maximum returns and at the same time economical fuel consumption, the carburetor of the chainsaw is required. Before adjustment, it is necessary to check the fuel and air filters. they must be clean. On most chainsaws, tuning is done with three screws: idle, high revs, low revs. The following signs indicate the correct carburetor setting:
- The chain does not idle.
- The engine accelerates smoothly and quickly.
- The sound of the running motor is even, similar to the sound of a four-stroke engine.
The carburetor adjustment must be treated with all possible care, because errors in the settings can lead to very serious consequences, up to the occurrence of engine malfunction. If there is no absolute confidence in your abilities, you must contact the service center.
Adjustment »Husqvarna Saw Carb.
For the break-in mode, so that the parts receive sufficient lubrication, the carburetor of the Husqvarna chainsaw is configured so that the maximum speed is 600–700 rpm. lower than working. If it is not possible to set the operating maximum frequency according to the tachometer, it is not worth changing the default settings with screw H. Exceeding the maximum speed value by the manufacturer is prohibited. If, after completing the adjustment, when the engine is idling, the saw chain moves, turn the screw T counterclockwise to force it to stop completely.
For precise adjustment, the saw must be warmed up for at least 10 minutes, installed on a flat surface. The tire should be pointing in the opposite direction from the person performing the tuning. At the initial stage, the highest value of the idling frequency should be detected. To do this, screw L is smoothly turned first from left to right, then vice versa. When the maximum revolutions are found experimentally, the screw L must be turned counterclockwise by a value from 1/8 to a quarter of a full revolution.
Idling is adjusted by a jet marked with the letter T. It must be turned from left to right until the chain starts to move. Then feed in the opposite direction until the chain stops spinning. The screw H is considered to be installed correctly if the noise of the saw at full throttle without load remains small. If the exhaust is too smoky and the saw is very noisy, the mixture is too rich. You need to turn the H jet clockwise until the correct sound is set. How to properly adjust the carburetor, you can see the video below.
Chainsaws Partner and Stihl, their adjustment.
In Stihl and Partner chainsaws, the proportion of air and gas in the mixture is set by adjusting screws H and L. When the screws are loosened, the mixture is enriched, rpm increases. Tightening leads to lean mixture and, consequently, lower engine speeds.
Setting the carburetor of the chainsaw Partner for idle is carried out by the T screw (Stihl marks this adjustment with the letters LA). Basic tool setup is done at the factory during the final tests. In most cases, the carburetor is adjusted to supply a slightly more enriched air-fuel mixture than the optimally calculated one. Settings set by the manufacturer must be saved in the first few hours of operation, during the break-in period. After that, finer adjustment can be carried out, although this is not necessary, the saw will work normally at the basic settings.
For fine adjustment of the carburetor, a tachometer is required, in addition, technical documentation is required to carry out work in strict accordance with the requirements of the manufacturer. The best solution is to entrust the jewelry tuning of fuel equipment to specialists.
If you decide to adjust it yourself, you should start with the screw L, then go to the jet H, and then set the idle speed by turning the screw T (or LA if it is a Stihl saw).
By smoothly turning the screw L in both directions, the position is sought at which the idle speed will be maximum. After this point is found, it is necessary to unscrew the screw L 1/4 turn. If the chain continues to move while the engine is idling, the T screw (LA) is slowly unscrewed until the chain stops.
After setting the maximum revolutions with screw H, the value of their frequency is checked by the tachometer. If the maximum speed does not correspond to the values indicated in the documentation, the adjustments are repeated. If at maximum speeds the mixture is too rich, too much smoke comes out of the muffler, when the mixture is poor, the saw makes a screeching sound and the engine gets too hot. The adjustment ends with the installation of idling. the position is considered correct if the motor runs smoothly at minimum speed and the chain is standing. The idle setting can be seen in the video below.
Custom carburetor Chinese chainsaw
The standard position for carburetors of the “Chinese” is the position of the screw L, in which it is weakened by one and a half turns from the fully clamped position. For screw H, one revolution from the same state. On many videos, screw L is called adjusting the quality of the mixture, and screw H is called its quantity. Idling is regulated in the same manner as described above on a warm engine.