How to adjust carburetor on STIHL chain saw

Adjusting the carburetor of the Husqvarna saw.

For the running-in mode, so that the parts get enough lubrication, the setting of the carburetor of a Husqvarna chainsaw is made in such a way that the maximum speed of 600-700 rpm. below the operating speed. If it is not possible to find the maximum operating speed given by the tachometer, you should not change the presetting value with the H screw. The manufacturer does not recommend to turn the saw more than the maximum rpm. If, after the adjustment has been completed, the saw chain moves when the engine is running at idle speed, turn the screw T counterclockwise to make it stop completely.

adjust, carburetor, stihl, chain

For the fine tuning of the saw it is necessary to warm it up for at least 10 minutes and place it on a flat surface. The bar should point in the opposite direction to the person making the adjustment. In the initial stage the highest value of the idling speed should be found. To do this turn the L screw slowly from left to right and then back to the right. When the maximum revolution has been determined by experiment, turn the L screw counterclockwise by one-eighth to one-quarter of a full turn.

The idle speed is adjusted by the nozzle, marked with the letter T. It must be rotated from left to right until the chain. Then feed it gently in the opposite direction until the chain stops turning. The H screw is set correctly if the noise is not excessive at full throttle and has no load. If the exhaust is too smoky and the saw makes a lot of noise. the mixture is too rich. It is necessary to turn the H jets clockwise until the correct sound is set. How to properly adjust the carburetor can be seen in the video below.

How to adjust the carburetor on a chainsaw

A diagram of how to adjust the carburetor and the recommended position of the adjustment screws is provided in the instruction manual for each tool. When familiarizing yourself with the new saw, it is recommended to tighten the screws to the end, while counting the number of revolutions, so that you can then return to the factory adjustments.

The basic principles of adjustment are as follows:

  • Before proceeding with the adjustment work it is necessary to warm up the engine at idling speed for about 10 minutes.
  • Performing the rotary actions with respect to the L turnboard it is necessary to adjust the mixture quality so that the idle engine would operate without a failure at 1500-2000 rpm. When you pull the throttle lever, the rpm should increase quickly and smoothly. If you notice that the revs sag, which is an indication of excessively lean mixture, turn the screw back a little at a time until the revs become stable.
  • After adjusting the mixture at low revs, turn the screw T up to the rotary motion of the chain and then unscrew it by 1/21/3 turn. Here it is important to make sure that the clutch mechanism is in good condition.
  • Do not adjust the “H” screw in a field situation. Unfavorable consequences of self-adjustment of the H screw is that a very lean mixture at higher rpm, and with increased load, as a result leads to accelerated wear of components of the internal combustion engine group on the saw and the failure of the ignition system.
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If three conditions are met, it is possible to make settings at higher rpm:

  • The chainsaw in operation does not perform its tasks with the necessary power when sawing.
  • The user who performs the tuning work has the information. How a carburetor engine works.
  • There is a means for measuring the engine rpm.

About the carburetor

The carburetor is used to mix the fuel-air mixture in pre-set proportions. If the clear doses are not respected, the serviceability of the motor is endangered. When during mixing the component comes a huge amount of air and not enough fuel, then such a mixture is considered “lean. Overdosing is also unacceptable, because a large quantity of fuel in comparison with air is also likely to cause malfunction or engine wear. Repair of STIHL chainsaw 180 with their own hands. 142, 240, 365 with their own hands. video. Adjusting the carburetor is needed not only before initial implementation, and when you identify any differences in his work. Before working with the chainsaw, be sure to run it in.

The construction of the carburetor has a standard set of parts, but may vary slightly depending on the manufacturer. Component parts:

  • Basics. Adjusting the carburetor with your own hands on. This is a special tube that visually resembles an aerodynamic design. Air passes through it. In a transverse direction in the middle of the pipe there is a choke. Its position can be adjusted. The more it is extended into the aisle, the less air enters the engine.
  • Diffuser. This is the connected part of the tube. It is used to increase the air flow rate in the segment where the fuel comes out.
  • Channels for fuel supply. The fuel mixture is in the float chamber, then travels to the nozzle from which it flows to the atomizer.
  • Float chamber. Is a separate constructional element, resembling the shape of a tank. Designed to keep optimal fuel level at all times before the air enters the channel.

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Adjusting the carburetor on your Husqvarna saw.

For running-in mode, so that the parts receive enough lubrication, the adjustment of the carburetor of the Husqvarna chainsaw is made in such a way that the maximum rpm was at 600-700 rpm. Below Duty Cycle. If you can’t set the maximum working RPM on the tachometer, you don’t need to change the preset speed with the H screw. It is forbidden for the manufacturer to exceed the maximum number of revolutions. If after completing the adjustment, when the engine idles, the saw chain moves, turn the screw T counterclockwise to force it to stop completely.

For the exact adjustment the saw has to be warmed up for at least 10 minutes and placed on a flat surface. The tire must point in the opposite direction from the person doing the adjustment. At the first stage the highest possible idle speed should be found. To do this, turn the screw L slowly from left to right, then vice versa. When the maximum turns have been found by experiment, turn the screw L counterclockwise by 1/8 to a quarter of a full turn.

The idle stroke is adjusted with a nozzle marked T. It must be turned from left to right until the chain starts to move. Then feed it gently in the opposite direction until the chain stops turning. The H jug is set correctly if the noise remains slight at full throttle and no load. If the exhaust is too smoky and the saw makes a loud noise, the mixture is too rich. Turn the H nozzle clockwise until it sounds right. You can see how to adjust the carburetor correctly in the video below.

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Need for adjustment

Throughout the operation process, there is a periodic need for additional adjustment and to ensure that the fuel-air mixture is delivered correctly. How to determine when and what adjustment is necessary for the equipment to function properly? There are telltale signs when the mechanism itself suggests from the behavior of individual parts when adjustment is needed.

First of all, each time before starting the engine, check the color of the spark plug electrodes.

By its change it is possible to decide on the necessity of adjustment, adjustment of working processes, improvement of the quality of the combustion mixture:

  • Black electrodes covered with soot or carbon deposits indicate an over-enriched air-fuel mixture entering the engine.
  • Brick-grey-colored electrodes indicate that the mixture is perfectly mixed and that no further adjustment is necessary.
  • White deposits on the spark plug electrodes indicate a lean mixture.

Signs 1 and 3 show that your STIHL 250 chain saw requires a carburetor adjustment.

Stihl Chainsaw Carburetor Adjustment

NOTE! A STIHL 250 manual carburetor adjustment may be necessary if the fuel quality or altitude changes or if there is poor air pressure in the area where the machine is operated. The air humidity, temperature, atmospheric pressure may have changed.

Precise adjustments allow you to get the best performance from the machine while reducing the external conditions necessary for its operation. Successful tuning of operating modes prevents oil starvation and engine failure due to insufficient lubrication. Because the lubricant enters the saw’s cylinder with a depleted fuel/air mixture.

Other problems

Chainsaw will not start

Before you start adjusting the carburetor, find out the cause of the possible malfunction. Consider situations that may arise:

Table

adjust, carburetor, stihl, chain

It is quite clear that before you do anything with the chainsaw, you need to understand why it does not work well.

First make sure you have a convenient place to make carburetor adjustments or repairs. It should be a level area, wide enough so that the parts stacked on it won’t get lost falling to the floor.

There is water in gasoline

Water in the gasoline

Gasoline has a lower density than water, so it will always be above the water in the tank. The chainsaw will not be able to work on this composition, so you need to get rid of what should not be in the tank by draining the.

To check if this is the case, you need to disconnect the fuel pipe from the carburetor and put it in a plastic bottle and drain the gasoline into it. As you can see in the photo. it will collect at the bottom. In that case, the carburetor should be disassembled and cleaned. If there is no water in the fuel, then return it to the tank and look for another fault.

How To Tune A Chainsaw | Adjusting The Carburetor

The properties of gasoline deteriorate over time, and the engine may not start just for that reason alone. In this case, the old fuel is drained and fresh fuel is poured instead.

Stihl ms 250 chainsaw carburetor adjustment stihl chainsaw carb adjustment tune up

Before adjusting the carburetor on your STIHL chain saw, check the spark plugs. By their condition and color you will be able to determine the need for the operation. If they have a black color, it indicates over-enrichment. If the color is brick gray, you can be sure that everything is normal. If there is white residue on the electrodes, the mixture is lean.

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It is the top screw that plays a major role in adjusting the carburetor. It is located next to the muffler. If you follow the factory setting, which you can find on the carburettor cover, you have to turn it by one turn. It is then adjusted. By unscrewing the screw, you make the working mixture more enriched, with more gasoline going into it. If the screw is screwed in, the working mixture will combine, with less gasoline in the fuel mixture.

Advantages and disadvantages

Zama carburetors are very reliable and easy to operate. The STIHL 180 has a carburetor on the STIHL chain saw that does not have the mixture quality and quantity adjusting screws that we are accustomed to. One screw makes it much easier to adjust.

The diaphragm carburetor has no significant disadvantages. With this carburetor, the chain saw works in any position. When sawing from the side, upright, etc.д.

Despite the aforementioned pluses, the carburetor is sensitive to fuel quality. In addition to clean air from the air filter, purified fuel from the gas tank must be fed to the carburetor. But this is not always possible, so at least once every six months it needs to be cleaned and blown out.

The need for adjustment

Throughout the life of your power tool, you will periodically need to fine-tune the settings and get the air-fuel mixture flowing properly. How to determine exactly when and what setting is necessary for the normal operation of the equipment? There are characteristic signs, when the mechanism, by the behavior of individual parts, itself prompts when adjustment is needed.

First of all, each time before the next start of the engine, it is necessary to check the color of the spark plug electrodes.

According to its change you can decide on the necessity of adjustment, adjustment of working processes, improvement of the quality of the combustion mixture:

  • Black electrodes covered with soot or carbon deposits indicate an over-enriched air-fuel mixture entering the engine.
  • Brick gray-colored electrodes indicate that the mixture is ideal in its composition and no additional adjustments are required.
  • White residue on the electrodes of the spark plug shows that the mixture is lean.

Signs 1 and 3 show that a carburetor adjustment is absolutely necessary for a STIHL 250 chain saw.

PAY ATTENTION! You may need to adjust the STIHL 250 carburetor yourself if the fuel quality or altitude changes, or if there is a vacuum in the area in which you operate the chain saw. The humidity in the air, the temperature, the air pressure might have changed.

Precise adjustments will allow you to get the most out of your machine while minimizing the external environment in which you operate it. Successful adjustment of operating modes prevents oil starvation and engine failure due to insufficient lubrication. the lubricant flows into the saw cylinder with the depleted fuel/air mixture.

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