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 are not affecting the operation of the engine 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.
Video: Carburetor Customization Chinese Chainsaw Video
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.
Husqvarna Saw Carb Adjustment.
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 still decide to adjust 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.