Adjusting the carburetor of the chainsaw ensures efficient operation of the tool at full power with economical fuel consumption. Adjustment should be made with a clean fuel and air filter. For a larger number of carburetors, the adjustment is carried out by three screws: for maximum and minimum speed and idle adjustment.
Screws H and L adjust the ratio of the gasoline-air mixture determined by opening the carburetor throttle. When the screws are loosened, the mixture is enriched, and the revolutions accordingly fall; when the screws are twisted, the mixture becomes leaner. the revolutions increase.
The designation H refers to the maximum speed screw that controls the main jet, L to the minimum speed screw that controls the idle jet. Screw S provides precise idle speed control. Sometimes, to simplify the adjustment, the number of carburetor adjusting screws available is reduced.
Setting the carburetor of the chainsaw is divided into two stages. the basic (factory settings), carried out with the engine turned off, and the final, made with the engine running warm. The exact angle of rotation should be taken from the operating instructions for the particular chainsaw. Failure to follow the manufacturer’s instructions could result in engine damage.
Basic carb adjustment.
The adjusting screws for the maximum H and minimum L revolutions are slowly turned clockwise until they stop, after which they are turned back 2 turns, other settings are also possible
Check and adjustment of idling.
We find the highest idle speed, for this, slowly turn the screw L in different directions. After finding the position of the highest engine speed, turn screw L 1/4 turn counterclockwise. If the chain rotates at idle, screw T or (S) should be turned by turning it clockwise until it stops.
Checking and adjusting the maximum speed.
Changing the maximum number of revolutions is carried out by screw H. When it is screwed in (clockwise rotation), the speed increases, when turned out, it decreases. Chainsaw engines have the highest rotation speed of 11,500 rpm. up to 15000 rpm Ignition does not provide a higher speed, in addition, it becomes dangerous for the engine. The maximum speed can be determined by interruptions in the ignition. If they come, screw H is slightly turned counterclockwise.
If the engine is not tested for acceleration and maximum speed, then the adjustment of the chainsaw cannot be considered complete.
With a smooth pull of the gas trigger, the engine must confidently and quickly gain speed from idle to maximum (from 2800 rpm to 11500-15000 rpm, depending on the unit). If the speed is slow, delayed, screw L must be slowly turned out counterclockwise, but no more than 1/8 turn.
After adjusting the acceleration and maximum revolutions, you should again check the operation of the saw at idle. the engine should work stably, the chain should not move. Chainsaw setting should be repeated if this condition is not met but with the exception of the basic adjustment step.
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.
Preparing for carb adjustment
Almost any UPT is regulated by 3 screws:
- 1. The bolt of the main jet, indicated "H" and used to set the maximum speed of the saw motor.
- 2. The idle jet bolt, indicated "L" and used for setting low revs. That is, for idle control.
- 3. The idle adjustment bolt, designated by different manufacturers in different ways: "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 PCT by determining the position of the tuning screw "L"at which idle speed will be greatest. 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 adjustment with the screw "S" ("LA", "T"):
- If the chain after handling the bolt "L" motionless, it is necessary to rotate smoothly "S" ("LA", "T") clockwise (hereinafter referred to as POMS) until it starts to move. Then twist "S" 1 / 8–1 / 4 turn back.
- If the chain moves, rotate "S" ("LA", "T") PSD, until it stops, and then twist "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 the accelerator is pressed smoothly, revolutions in a short time and without "failures" increase to its maximum value. If the engine does not work smoothly and / or accelerates poorly, then it is necessary to tighten slightly. a maximum of 1/8 of a whole revolution. "L" PSD. After this, you must again make the above settings "S" ("LA", "T") We repeat these adjustments until the motor starts to work evenly and accelerate well.
Checking the operation of the chainsaw
Now check the setting 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, it is necessary "H" tuck a little pochs. 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 "H" Turn 1/4 of the turn of the emergency speed response.
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.
Video: Carburetor Tuning Stihl 230 Chainsaw
If these conditions are not fully complied with, you should 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.
In the first step, the adjustment screws "L" and "H" slowly screw POSH to 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 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. Screw in slowly "S" PShD all the way.
We pass to the final stage. We are trying to start the engine. If there were no manipulations with the adjustment "S" ("LA", "T") and exactly as recommended "L" and "H"then it should start.
If "S" had to be twisted for the reasons stated above, the motor 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 or during warming up the motor is unstable or the chain starts to move, then it is necessary to slowly and carefully rotate "S" ("LA", "T") PSD. 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, idle speed may begin to increase, then, again, it will be necessary "S" ("LA", "T") start slowly tucking 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. Starting with a bolt "H". After setting the maximum speed, check idle. If they are different from normal, set them first with "L", and then "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. Fully spin "LD" EMR before its tight fit.
- 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 too low. twist "LD" POPS, until the chain starts to move, after which we turn this bolt 1/2 turn back, SRPS;
- the tool chain moves at idle. slowly twist "LD" PSRP until it stops, after which we turn this bolt an additional 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 basic setup (discussed in the third chapter) "L" and "H" after twisting, turn back by 1 revolution. There are also saws with a carburetor, in which the basic setting "H" makes 3/4 turns. 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.
The internal combustion engine of a chainsaw requires special attention due to the harsh operating conditions, and especially with the carburetor. Without periodic maintenance, no motor system will last long. Today we will talk about the process of adjusting and eliminating various malfunctions.
Chainsaw carburetor device
To independently adjust the carburetor of the chainsaw, you do not need to be a professional motor technician. However, you still have to learn some aspects of the carburetor operation related to the process of preparing the fuel mixture.
The vast majority of chainsaws are equipped with Chinese-made Walbro carburetors. In their device they are simple, if not primitive. There is a one-piece block-type housing with a through hole. Inside the hole there is a diffuser. narrowing the passage with the fuel injection channel. There are dampers on both sides: the smaller one is the throttle, it controls the amount of fuel mixture to be fed into the cylinder. A larger damper. air, serves to limit the flow of air during a cold start.
Walbro carburetor device: 1. inlet fuel fitting; 2. pulse channel of the diaphragm pump; 3. inlet valve; 4. a membrane of the fuel pump; 5. exhaust valve; 6. filter mesh; 7. air damper; 8. throttle valve; 9. a fuel channel; 10. idle adjustment screw; 11. a needle; 12. idle jets; 13. a control membrane; 14. a fuel chamber; 15. main jet; 16. diffuser; 17. the main adjusting screw
All the magic of fuel preparation takes place in the hidden channels and chamber of the diaphragm pump. When the throttle is turned, the cross-section of the channel through which fuel is injected into the mixing chamber increases slightly and fuel enters in a larger volume. At the same time, the carburetor has two kind of valves: for feeding at low and high speeds. When changing the throttle position, the fuel flow changes proportionally between these two valves.
The need for such a device is that at idle and under load, the quality of the mixture should be different. At the same time, the channel through which fuel is fed into the mixer at idle does not completely overlap during engine acceleration, and vice versa. the maximum speed channel is slightly corroded at idle.
Do I need disassembly
You can adjust the chainsaw carburetor without any disassembly at all, with rare exceptions you only have to remove the air filter cover. There is a considerable share of controversy: on the one hand, the chainsaw is designed for unhindered access to the adjustment mechanism, and on the other, it is recommended to access it as little as possible.
True, experienced fellers and filers always carry a flat screwdriver with a long sting and periodically adjust the carburetor. The explanation is simple: in the manufacture of a chainsaw, its carburetor undergoes a rough adjustment, designed for a specific composition of air and fuel. It is clear that the conditions at the place of work differ from the bench.
When changing the brand of gasoline or, for example, increasing air humidity, an experienced user of a chainsaw will always adjust the quality of the mixture for greater productivity and less wear on the piston. But this, we repeat, requires considerable experience working with a particular chainsaw and knowledge of the features of its behavior. In addition, the adjustment is incredibly thin. the screws tighten only 1/10. 1/20 turn.
Another reason to adjust is to repair or replace the carburetor. In any case, adjusting the quality of the mixture should be carried out only if the health of the carburetor is reliably known (no debris, gaskets are not poisoned), the air filter is clean, the spark plug, clutch and ignition system are in perfect order. Otherwise, it is likely that the malfunction will be eliminated at one point and the adjustment will become abnormally abrupt, and the engine will start to wear.
Basic adjusting screws
There are only three organs for adjusting the carburetor, these are spring-shunted screws for a flat screwdriver. Below is a pair of screws, on the left is L, on the right is H. A little higher is screw T (or S). So here is what they are for:
- Screw L. this is the same valve that regulates the cross section of the fuel channel when operating at low speeds.
- Screw H, by analogy with the previous one, is a channel flow regulator for high revolutions.
- Screw T is a throttle control. It determines its position with the accelerator lever fully released.
The device of the first two adjusting screws is extremely simple: at their end there are needles inserted into spools of variable section (cones). The thread is right for everyone, so turning the screw clockwise, you drive the needle deeper and lower the duct. When counterclockwise, the exact opposite happens.
Thus, the quality of the mixture in different operating modes is regulated. If the fuel content increases, gasoline does not have time to burn out completely and the engine develops rpm worse. With a lean mixture, rpm, on the contrary, grows, and at the same time, the engine temperature rises. It is worth noting that even when tightening the screws to the stop, the duct of both channels does not completely overlap, unless there is a blockage.
The carburetor setting chart and the recommended position of the adjusting screws are indicated in the instructions for each specific tool. When meeting a new saw, it is recommended to tighten the screws all the way, counting the number of revolutions, so that later you can return to factory settings. The general principles of adjustment are as follows:
- Before adjusting the engine, warm it up at idle for 10 minutes.
- Turning the screw L it is necessary to achieve such a quality of the mixture that at idle the engine runs uniformly at 1500–2000 rpm. At the same time, acceleration (acceleration) when pressing the accelerator lever should be fast, but uniform. A failure in the set of revolutions indicates a too lean mixture, the screw must be unscrewed until this phenomenon disappears.
- After adjusting the mixture for low revs, screw T is tightened until the chain starts to rotate and then is twisted 1/2. 1/3 turn. It is important to monitor the health of the clutch mechanism.
- Screw N in artisanal conditions is not regulated.
The danger of self-adjusting the screw H is that too lean mixture at high speeds, and especially under load, leads to rapid piston wear and malfunctions in the ignition system. Climbing to adjust the high revs is possible only if three conditions are met:
- Chainsaw obviously does not give the required power when sawing.
- The person performing the adjustment has a general knowledge of the design of carburetor engines.
- A means for measuring engine speed is available.
The last can be either a tachometer or a multimeter with a built-in oscilloscope. To connect the multimeter, you need to wrap 3-4 turns of thin copper wire around the spark plug wire.
The main objective of screw N is to compensate for excess or understatement of revolutions due to a change in fuel type, oil concentration or air composition. Also, the “upper” setting can be knocked out by insufficient accuracy of adjustment of the low-speed screw. The adjustment scheme is simple. the screw is tightened or unscrewed until the saw engine at maximum gas produces 14.5-15 thousand rpm or the value specified in the operating instructions.
If you use an oscilloscope, its readings (spark discharge frequency) should be in the region of 230–250 Hz. Consider the accuracy class of measuring instruments and the fact that under load the revolutions sag by 10-15%. It is better if the engine runs at low revs than at high, albeit slightly.
As a conclusion, we describe typical malfunctions associated with improper carburetor adjustment and methods for their elimination:
- The engine will not start or start and will stall after a few seconds. Obviously, the reason for the incorrect adjustment of the quality of the mixture at low speeds, it is too poor. With a working carburetor, you need to slightly enrich the mixture by unscrewing the screw L 1/2 turn, and then complete the setting with screw T.
- The engine under load noticeably loses in power. In this case, the carburetor produces a too rich mixture at high speeds. Screw N must be tightened by 1/8 turn if the engine load is still not sufficiently supported, but progress is noticeable. tighten a little more.
- The engine "sings" at maximum acceleration without load. The mixture at high speeds is too lean, the speed is too high.
- Engine stalls if gas is applied after idling. Too poor or rich mixture, more precisely, can be said by the state of the candle.
Please note that carburettor settings may be lost due to strong vibration. For this reason, a well-chosen adjustment must be remembered by counting the turns and the position of each adjustment screw. If you have determined the best type of gasoline and oil ratio, save a small portion of such a mixture so that in case of malfunctions, check if the malfunctions are connected with the quality of the fuel and the wrong adjustment, or if the chainsaw is malfunctioning.