Adjusting The Chainsaw Carburetor.

A chainsaw is an indispensable tool, both in the household and on the dacha. But even the most reliable “iron” assistant begins to be depressed, it does not start, then stalls. The reasons can be many, both related to the quality of the fuel mixture, and with the engine.
There are a lot of nuances, and we will not consider all of them in this article. A “look” we to the part of the engine, which is called the carburetor. And we will try to find the answer to the following questions: when adjustment of the carburetor of the chainsaw is necessary and what is the scheme of such adjustment.

Chainsaw carburetor arrangement.

Before proceeding with the adjustment, it is necessary to know the structure and operation of the carburetor. It will help avoid many “complications.” So, to begin with, let us recall the principle of operation of an internal combustion engine. There is fuel in the cylinder, when burning a small “explosion” is created, which creates a lot of pressure. This pressure pushes the piston, the piston, when set in motion, rotates the crankshaft. Ultimately, the pressure energy is converted into a rotational moment, which drives the chain through an asterisk.
During normal operation of the engine in each cycle, it burns only up to 10 milligrams of fuel. And the fuel mixture in the carburetor is prepared and supplied.
Thus, the purpose of the carburetor is to mix the combustible mixture with air in the required proportions. If these proportions are violated. the engine is disrupted. For example, when mixing there is little fuel, and on the contrary, there is a lot of air, this mixture is called “poor”. Conversely, if there is not enough air, and vice versa there is a lot of fuel, then it is a supersaturated mixture. Both cases lead to malfunctions in the normal operation of the engine and require adjustment.

The carburetor consists of the following basic elements, and although the design may differ depending on the model, the device and the principle of operation are approximately the same:

  • the base of the carburetor is a tube, in its characteristics resembling a wind tunnel, through which air flows;. across the tube, there is an air damper; by its position, it either increases the airflow or reduces it;
  • the tube has a narrowing. a diffuser, which increases the speed of the airflow just at the place where the fuel outlet is located;
  • the fuel itself enters the air channel from the atomizer, into which it enters through the nozzle from the float chamber (shown in the photo as a fuel needle);
  • the float chamber itself serves as a kind of reservoir, the purpose of which is to provide a constant level of fuel at the entrance to the air channel.

The principle of the carburetor work is so. Through the air channel flows a rapid flow of air, its speed will depend on the position of the valve. The float level provides the degree of opening of the fuel supply channel and depends on the position of the same air damper. The airflow, passing through the diffuser, picks up the incoming fuel, sprays it. At this point, a mixture is formed, which is sucked through the inlet pipe into the cylinder.
In the float chamber, the pressure level is approximately equal to the atmospheric pressure, but in the air channel, it is rarefied. Due to the pressure difference, fuel is sucked through the jet into the air channel. The more open the air damper. the higher the flow of air, and accordingly, the more significant the flow of fuel. fuel. engine speed increases.
It is the principle of the carburetor. There may be nuances in its structure, but knowing how the simplest carburetor works, you can always understand and determine the purpose of other elements.

In what cases adjustment is necessary?

In general, the need to adjust the carburetor chainsaw Stihl, or any other brand occurs quite rarely.

Signs of a deregulated carburetor are indicated by:

  1. the engine starts and stalls, or does not start. in this case, the cause may be a “poor” fuel mixture;
  2. significantly increased fuel consumption and an increase in the number of exhaust gases (fuel does not burn completely). the cause may be a supersaturated mixture.

By itself, the adjustment gets off in very rare cases, namely:

  • when the fixing screws are broken, there are three of them. The cause may be vibration or damage to the protective cap. It would be quite a rare case if no one touched the screws.
  • in case of significant engine wear, namely piston. Then the factory settings are not suitable. In this case, adjusting the carburetor chainsaw Patriot, or another model can save the situation for some time. But here it is just right to think more about repairing the engine, rather than adjusting the carburetor of the Husqvarna chainsaw or the like;
  • the reason may be due to the formation of a blockage in the carburetor, the cause may be the poor quality of gasoline, damage to the air filter, or dross. In this embodiment, in addition to adjustment, disassembly and washing of the carburetor is necessary.

Adjusting the chainsaw carburetor.

Although quite rare, it may still require adjustment of the carburetor. Immediately, we note that not everything can be done independently, except that you have a tachometer and see for yourself at least once how to do it correctly.
For the adjustment of the carburetor chainsaw Makit, like most other models are three adjustment screws. Although some manufacturers carefully removed two of them, leaving only one for user experiments.

So, three screws, on the body of the carburetor, they are indicated by the following letters:

  • L. with the help of this screw adjustment of the low engine speed is made;
  • H. high speed adjustment;
  • T. to adjust the idle speed (and leave it for experiments).

In general, the carburetors are already adjusted by the manufacturer for optimal operation, and the screws are designed for more accurate adjustment of the carburetor Champion chainsaws and others, in difficult climatic conditions such as high mountains, etc. Since the air, there is more rarefied, more precise adjustment is necessary for the operation of the instrument. Under normal conditions, this is not necessary.
To adjust the carburetor of the Goodluck chainsaw, as well as other brands, two screws L and H are used to create the appropriate quality of the fuel mixture. To create a lean mixture, the screws are turned clockwise. It allows increasing the number of revolutions, thus, expose high turns. Accordingly, when the screws are turned counterclockwise, the mixture turns out to be more saturated, this adjusts the low number of engine revolutions. Thus, when adjusting the carburetor of the chainsaw Partner, by turning the screws clockwise, we increase the number of revolutions, counterclockwise. we reduce.

In any adjustment of the carburetor Chinese chainsaw or other must comply with several requirements:

  1. fine adjustment is always carried out with a warm engine (engine running at least 10 minutes);
  2. the condition of the air filter must be satisfactory, i.e. clean and not clogged;
  3. when rotating the chain with the help of the adjusting screw T, it is necessary to achieve its complete stop, for this, the screw rotates counterclockwise.

And do not forget about our safety, the chain should be directed in the opposite direction to us, the saw should stand securely on a flat surface and not touch the cutting part of any objects. With the fine adjustment, the screws are adjusted in the following sequence L. H. T. With the help of screw L, and it is necessary to “find” the maximum number of engine revolutions. To do this, turn the screw clockwise, or in the opposite direction, until we “feel” the maximum. It is where you need a pressure meter or a sensitive ear for music, and you should know the sound of the engine’s extreme revolutions, especially if you overdo it, especially with the H regulator. the engine will fail. The repair will cost a lot of money. Therefore, we strongly recommend that you entrust such work to a professional.
If you have a tachometer in your possession and know the maximum number of revolutions of your engine, then you can, at your peril and risk, try to complete the adjustment. It will look something like this: we find the closest speed value with the L regulator, then with the same regulators we return counterclockwise to the fourth part of the screw rotation. We leave and proceed to the regulator H, and if it is excessively tightened. the engine will fail.
This regulator is turned on ¼ of a turn of the screw counterclockwise (we warm up the engine before this). Listen carefully or focus on the tachometer. If the sound. our ideal, when the engine at maximum works as a four-stroke engine. With too rich a mixture. the sound is squealing. You can try to achieve an average value, not have an ideal, but remove the squealing noise with a screw. And if the work of the saw suits you, it is better to leave it, as it is, it is better than to remain without an engine.
If it was possible to more or less adjust the screws L and H, then there was a little bit left. to change the idling speed. The idea here is to ensure stable operation of the engine in all positions until the chain begins to move. Turn this screw counterclockwise until the chain stops. If this cannot be achieved, then specialist assistance is needed. An unregulated chainsaw is a dangerous thing.

Well and properly adjusted carburetor are:

  • the chain idling “stands”;
  • engine accelerates quickly;
  • engine operation resembles a four-stroke engine.