How to adjust carburetors of chainsaws from different manufacturers?

“A carburetor is a device responsible for the mixture and supply of fuel to the combustion chamber of an internal combustion engine.”
I am glad to welcome all lovers of “interesting and necessary men’s toys.”

Correct carburetor adjustment ensures reliable operation of the chainsaw in all modes and with economical fuel consumption. However, if we remove the word “chainsaws”, then this applies to all internal combustion engines.

Today we’ll talk about how to adjust the carburetor on a chainsaw. In general, such a procedure is performed occasionally. Factory setting is the best and highest quality option. However, if necessary, it is performed by adjusting special screws. Let's figure out how to rebuild it yourself:

Basic malfunctions when using gasoline saws

You should start adjusting the carburetor only after making sure that the cause of the malfunction is due to a malfunction in its operation. Therefore, it is necessary to analyze the possible causes of failure in the operation of a gasoline engine. Table 1 shows the main malfunctions and causes of their occurrence in most models of gasoline tools.

Table 1: Main malfunctions in engine operation and solutions.

Users note the main signs when carburetor settings are violated:

1. The engine starts with great difficulty or cannot be started at all.
2. During operation, dips are observed when pressing the throttle control lever.
3. The engine cannot develop the required power; when the throttle is fully opened, a stop is possible.
4. Excessive level of smoke, increased noise during operation, accompanied by shots in the intake tract.
5. Unstable operation in different modes.
6. Low rotation speed of the chain drive when setting to automatic maintenance mode.
7. Increased gasoline consumption when performing work. The sign is very subjective, based on a comparison of indicators during different periods of operation.
8. Clogging of the intake system when removing the air cleaner. It is also possible that the material used for air purification may become clogged.
9. Wear of the cylinder-piston group. Carburetor adjustments will have a temporary effect.

Attention! If dirt gets into the power system, you will have to not only regulate it. There will be a need to wash individual components and parts.

This video shows the simplest option for purging the intake system:

Advantages

Husqvarna AB saws have always been and are considered one of the best. To this day, the company uses only the most advanced technologies in the production of chainsaws. Each saw has a common set of features, and there is an individual one, used only on a specific chainsaw or category of saws. For example, on all powerful professional Husqvarna chainsaws, a decompressor is installed to make starting easier - individual. A common feature is an engine with X-Torq technology, used on all saws to save fuel and reduce emissions of harmful substances into the atmosphere.

Let's see what features chainsaw .

• Air Injection system - extends the service life of the air filter, thanks to an effective air purification system, the filter can be changed much less frequently;
• quick-release air filter mount - the replacement process has become much faster;
• Auto-shutter ignition switch—automatically returns the switch to the ON position to facilitate restarting;
• crankshaft made of 3 parts - technology has made it possible to significantly increase the service life of the crankshaft;
• primer - fuel priming pump;
• Smart Start system - according to the developers, it ensures easy starting of the saw by reducing the cord resistance at start-up by 40%;
• LowVib is a vibration reduction system that effectively protects a person from harmful effects during work;
• X-Torq fuel saving and emission reduction system;
• easy and convenient refueling thanks to the hinged fuel cap;
• chain tensioning without additional tools - on the Husqvarna 450 e no additional tools are needed to tighten the chain (a very convenient function).

Husqvarna.Idle increase.Carburetor repair.carburetor adjustment

The list contains only the most interesting advantages of the Husqvarna 450 e chainsaw. For the bigger picture, it is also worth noting the presence of an ergonomic handle with inserts made of soft materials, a cylinder cover with latches (allows quick access to the filter, spark plugs), fuel level indication; chain brake; markings to guide the felling of trees.

Carburetor design

The preparation of the working mixture supplied inside the internal combustion engine occurs in the carburetor. The fuel mixture should contain up to 13...15 parts of air per part of fuel. Then complete combustion will occur when a spark is applied.

• If the fuel concentration decreases and air increases, a lean mixture is formed. The combustion process occurs more slowly.
• The gas pressure on the piston during the working stroke will be lower, which will lead to a decrease in torque.
• Quite often, engine overheating is observed, since afterburning occurs during the exhaust phase.
• A rich mixture is characterized by increased fuel supply and reduced air charge concentration.
• Due to the lack of oxygen for complete combustion, carbon deposits form. It deposits in the exhaust tract and clogs the muffler. Causes engine overheating.
• Black smoke is observed in the exhaust.

Stable operation is possible only with an optimal ratio of components of the combustible mixture. This is achieved by adjusting the position of the control needles in the carburetor. The manufacturer supplies the device with a nozzle; a calibrated hole is drilled in it, through which fuel is supplied to the diffuser.

Carburetor diagram: 1 – fuel supply fitting; 2 – channel for supplying air pulses to the fuel pump membrane; 3 – fuel inlet valve; fuel pump (diaphragm); 5 – valve for releasing fuel from the fuel pump; 6 – filter element for the fuel mixture; 7 – air damper, which is closed when starting and warming up the engine; 8 – main throttle valve, which regulates the engine operating mode and its power performance; 9 – fuel supply channel for mixture formation; 10 – idle speed adjusting screw (ISR); 11 – needle in the fuel supply system; 12 – idle jet; 13 – membrane; 14 – fuel accumulation chamber in the carburetor; 15 – carburetor main jet; 16 – diffuser, the main evaporation of fuel occurs here; 17 – screw for adjusting the fuel supply through the main jet.

Fuel supply system

Using your Husqvarna chainsaw incorrectly will prevent fuel from entering the master cylinder. This problem occurs for several reasons:

• Dirty close fuel
  filter;
• Viscous chain oil,
• Clogging of the special hole;
• Dirty air filter.

To clean your chainsaw's fuel hose, carefully check the fuel supply. Experts recommend replacing the old hose every three months and purchasing a new part. If the air hose is dirty, no air can enter the system, namely the carburetor. Most often this leads to engine malfunction.

The filter can be cleaned with plain water, but this procedure must be done very carefully

The part is thoroughly dried and installed in its original place. Husqvarna chainsaw

137 is sold with instructions on how to replace and clean the hoses. If you don't follow the rules, the situation can get worse.

The most common reason. This is a clogged channel or damage to the carburetor membrane. In this case, it is recommended to replace the part and clean the channels. After this, the chainsaw will work smoothly.

Carburetor operation

When starting the internal combustion engine, the air damper closes. This mode produces a rich mixture. The engine gradually warms up:

1. The cylinder walls heat up.
2. Heat is transferred to the fuel chamber, the fuel temperature rises, which improves its evaporation during external mixture formation.

The filter elements do not allow abrasive particles contained in the surrounding air to enter the cylinder.

• After warming up, you can open the air damper. Correct idle speed control is responsible for stable operation.
• During operation in a converging diffuser, the air flow moves at high speed. Fuel is sucked into the diffuser, it evaporates, and a working mixture is formed.
• When the throttle valve is opened, the amount of charge supplied increases.
• The turnover is increasing. Power and torque are also higher.
• By closing the throttle, the flow of charge is reduced. Power is reduced.

To regulate the carburetor, there are adjusting screws; they are located on the control panel. The operating mode is set by the position of the levers associated with the damper and throttle. For ease of control, cables are attached to them.

How to remove the carburetor?

1. In order to remove the carburetor, you need to unscrew 2 nuts.
2. A key of 13 is used.
3. The levers are disconnected from the cables.
4. The supply hose from the gas tank is removed.
5. Rock the carburetor left and right and pull it out.
6. The engine inlet must be closed with a plug or clean cloth.
7. The fuel hose is bent. You can put a nut on it, as shown in the photo. Then gasoline will not leak out.

Adjusting the Husqvarna chainsaw carburetor

General view of the Husqvarna chainsaw carburetor and adjusting screws:

A distinctive feature of this saw is the ability to operate at low idle speeds. In the instructions, the manufacturer notes the following: on a correctly adjusted device, the minimum idle speed is 600...700 rpm. If work occurs at a higher crankshaft speed, the chain will not stop in idle mode. This is dangerous for the user.

To correctly adjust the carburetor, place the chainsaw on a horizontal surface.

Before starting the adjustment, you need to allow the internal combustion engine to warm up for 8...10 minutes (in summer) or 12...15 minutes (in winter, at negative air temperatures).

Turn screw L on the carburetor clockwise. Having reached the limit position, they return back approximately a quarter turn counterclockwise.

The idle speed is set with a screw marked T. Turn this screw clockwise and watch the chain begin to move. As soon as the chain starts to move, turn the screw back until the drive sprocket stops rotating. The chain will stop.

Screw H determines the quality of the mixture at maximum speed. If you turn it clockwise all the way, the internal combustion engine will make a lot of noise. The exhaust will be smoky and the mixture will be too rich in the carburetor. Therefore, from the maximum position, reverse rotation is performed approximately half a turn back.

Recommendations for adjusting the carburetor on Husqvarna saws are shown in the video:

Reviews

Advantages: powerful, comfortable, not noisy, low fuel consumption.

Review: Husqvarna 450 is the first chainsaw that I have used, so there is nothing to compare it with, but I am completely satisfied with the result of the work. I recommend.

Advantages: among the advantages, I would like to note easy starting and quick tensioning of the chain, more than enough power for my work.

Disadvantages: price, I would like the price tag to be lower.

Review: I often have to start the Husqvarna 450 chainsaw in the cold, no complaints, it starts without problems, and besides, it starts somehow easily for its engine size. I tried a tire larger than 50 centimeters - I don’t recommend it, it doesn’t fit. With a standard chainsaw, the chainsaw perfectly fells birch trees 50 centimeters thick.

Adjusting the carburetor of Stihl and Partner chainsaws

General view of Stihl and Partner:

Stihl chainsaw carburetor:

Partner chainsaw carburetor:

Despite the external differences, the carburetor design of gasoline saws from these manufacturers is the same. The minimum rotation speed of the internal combustion engine crankshaft is 700…800 rpm. At this frequency the chain does not move.

Adjustment is recommended when installed on a horizontal support.

• Warming up is carried out until a stable operating mode is achieved. If the adjustments are violated, you have to periodically press the throttle lever.
• Using the XX screw, the chain begins to move, and then by reverse rotation, the mode is set when the chain does not move.
• Screws L and H set the maximum speed and mixture quality. Turn it all the way, and then turn it back half a turn.

The video shows the Shtil carburetor adjustments:

Attention! On Stihl carburetors, sticking of the valve in the nozzle is quite often observed. Most often, this phenomenon occurs when the saw is stored improperly. Some users forget to completely drain the fuel before long-term storage. The valve sticks to the body. When gasoline evaporates, only oil remains. It promotes adhesion. You have to carefully disassemble the device and wash it thoroughly.

Carburetor repair video Partner:

Conclusion

The work of adjusting or repairing the carburetor on Husqvarna chainsaws can be done without any specific experience. In order to do everything correctly, you must follow the algorithm and have a minimum set of tools. It’s also worth assessing your strengths in advance and not taking risks if you don’t understand anything at all about technology. Believe me, sometimes it is better to pay a small amount to the master than to ruin the instrument by adjusting it yourself.

Source