Possession of a chainsaw makes life much more comfortable 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 improper or not very high-quality maintenance, as well as, as a result of exposure to both planned and excessive loads, various kinds of malfunctions can occur. For professionals, interruptions or unstable work of the saw reduces work efficiency or may cause a damaged working day. One of the reasonably common problems is the incorrect setting of the carburetor of the chainsaw, which is lost due to unsuccessful attempts to adjust or shift the adjusting screws for other reasons.
Symptoms of malfunctions and breakdowns that require carburetor adjustment.
The following symptoms and faults indicate the need to adjust the carburetor:
- the engine starts up with an effort and stalls almost instantly;
- gasoline consumption is too high, the exhaust is too thick, the combustible mixture in the cylinder does not burn completely;
- shot down the factory settings of the carburetor chainsaw (due to vibrations or unsuccessful attempts at regulation);
- malfunctions of the air cleaning system, leading to the entry of debris into the mechanism that distributes the fuel mixture;
- considerable wear of the piston group. the carburetor setting, in this case, acts as a temporary measure.
It is clear that when dirt gets into the fuel system with one set, the problem cannot be solved. we need to flush it. In the case of piston wear, a major overhaul is required. However, in all these cases, the carburetor setting is also carried out.
Purpose, design and principle of the carburetor.
The carburetor is needed to prepare the air-fuel mixture to power the engine. If the proportions in this mixture are wrong, the engine is disrupted. If the proportion is not observed in the direction of an increase in the amount of fuel, the mixture is called supersaturated, if, on the contrary, the fuel is low. lean. On the operation of the engine and the one and the other affects not the best way.
In different models of chainsaws, carburetors differ in design, but they are similar in the principle of operation. Airflow at high speed moves through the air channel. The shutter blocking the channel allows you to change the speed of the air jet. 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 there is fuel 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 damper opens, the faster the air moves, and the amount of fuel also increases. the engine speed increases. So, you can imagine the principle of carburetor.
For effective, smooth operation of the tool, maximizing returns, and at the same time-saving fuel consumption, it is necessary to adjust the carburetor of the chainsaw. Before adjustment, check the fuel and air filters. they must be clean. On most chainsaws, tuning is done with three screws: idling, high revs, low revs.
The following signs indicate the correct setting of the carburetor:
- The chain does not move idling.
- The engine accelerates smoothly and quickly.
- The sound of a running engine is even, similar to the sound of a four-stroke engine.
By adjusting the carburetor should be treated with all possible accuracy, because errors in the settings can lead to severe consequences, up to the occurrence of engine malfunction. If there is no absolute confidence in their abilities, you should contact the service center.
Adjusting the carburetor saw Husqvarna.
For the run-in mode, for the parts of receiving lubrication in sufficient quantity, the setting of the carburetor of the Husqvarna chainsaw is made in such a way that the maximum speed is 600–700 rpm. below working. If it is not possible to set the working maximum frequency on the tachometer, you should not change the presets with the screw H. Do not exceed the maximum number of revolutions by the manufacturer. If, after completing the adjustment, when the engine is idling, the saw chain moves, then turn the screw T counterclockwise to force it to stop completely.
For fine adjustment, the saw must be heated for at least 10 minutes and installed on a flat surface. The tire must be directed in the opposite direction from the person performing the adjustment. At the initial stage, the highest idle frequency should be detected. To do this, screw L smoothly turn first from left to right, then vice versa. When maximum turns are experimentally found, it is necessary to turn the screw L counterclockwise by a value from 1/8 to a quarter of a full turn.
Idling is adjusted by the jet, marked with the letter T. It must be turned from left to right until the chain starts moving. Then smoothly apply in the opposite direction until the rotation of the chain stops. Screw H is considered to be set correctly if the noise of the saw operation with full gas without load remains small. If the exhaust is too smoky and the saw is very noisy. the mixture is too rich. It is necessary to turn the jet H clockwise before setting the correct sound. How to adjust the carburetor correctly, you can see on the video below.
Chainsaws Partner and Stihl: adjustment.
In chainsaws Stihl and Partner, the adjusting screws H and L expose the proportion of air and gasoline in the mixture. When the screws are loosened, the mixture becomes enriched, the speed increases. Screwing leads to depletion of the mixture and, consequently, a decrease in engine speed.
Setting the carburetor of the chainsaw Partner at idle speed is carried out with a screw T (Stihl marks this adjustment with the letters LA). The essential tool setting is done at the factory during the final tests. In most cases, the carburetor is adjusted to supply a slightly more enriched fuel-air mixture than the optimal calculated one. The settings established by the manufacturer must be kept in the first few hours of operation during the run-in period. After this, a more fine adjustment may be carried out, although this is not necessary, the saw will also work normally on the basic settings.
A tachometer is required for fine adjustment of the carburetor. Besides, technical documentation is needed to carry out work in strict accordance with the requirements of the manufacturer. The best solution would be to entrust jewelry tuning of fuel equipment to specialists.
If it is nevertheless decided to adjust independently, one should start with screw L, then proceed to the nozzle H, then expose the idling by turning the screw T (or LA. if it is a Stihl saw).
A smooth turn of the screw L in both directions will look for a position at which the idling speed will be maximum. After this point is found, you need to turn the screw L 1/4 of a turn. If the chain continues to move while the engine is idling, the screw T (LA) is slowly unscrewed until the chain stops.
After adjusting the maximum revolutions with the screw H, the value of their frequency is checked using a tachometer. If the speed at the maximum does not correspond to the values specified in the documentation, repeat the adjustment. If at maximum speed the mixture turns out to be too rich, too much smoke is emitted from the muffler, with a poor mixture the saw makes a screaming sound and the engine is too hot. The adjustment ends with the installation of idling. they consider the position to be correct if the engine runs exactly at the minimum speed and the circuit is worth it. Installation of idling can be viewed on the video below.
Setting up a Chinese chainsaw carburetor
The position of the screw L at which it is loosened by one and a half turn from the fully clamped position is considered to be standard for the “Chinese” carburetors. For screw H. one turn from the same state. On many videos, the screw L is called the adjustment of the quality of the mixture, and the screw H is called its quantity. Idling is regulated in the same way as described above on a warm engine.
The position of the screw L at which it is loosened by one and a half turn from the fully clamped position is considered standard for the Chinese “carburetors”. For screw H. one turn from the same state. On many videos, the L screw is called the mixture quality adjustment, and the H screw is called its quantity. Idling is regulated in the same way as described above on a warm engine.