Tuning The Carburetor Of The Husqvarna 240 Chainsaw
How to adjust the carburetor on a chainsaw and properly adjust the idle speed with your own hands
Chainsaw carburetor adjustment is performed in several stages. It is necessary to assess possible problems in operation and the condition of structural elements, and then carry out adjustment measures.
How to adjust the carburetor on a chainsaw and properly adjust the idle speed with your own hands
For self-tuning the carburetor, you need to familiarize yourself with its device and remember the order of work that is carried out to adjust the parts that are responsible for the correct functioning of the constituent elements of the device and nearby parts. It is necessary to carefully handle objects for adjusting the chainsaw system, as well as to determine the correspondence of the set parameters to the maximum permissible values.
Checking acceleration work
A little research needs to be done. The acceleration of the device is initiated. The serviceability of the engine should be assessed during the maximum revolutions. When the engine is functioning properly it means when you press the accelerator, the speed quickly increases to 15,000 rpm.
The adjusting screws for the highest and lowest speed should be moved clockwise until the highest resistance is encountered. When the screws reach the stop, you need to move them in the opposite direction and leave them after 1.5 turns.
How to properly tune a Chinese saw. Adjusting instructions
In order to correctly configure the carburetor of a Chinese chainsaw, you must first remember the factory settings of the device, then turn on the engine. Subsequently, you will have to leave it to work for several hours in order to accurately set your own parameters. Sometimes the work is performed once after ten minutes of engine operation, but many Chinese-made models require special handling.
- Activities start in idle mode. With the help of the adjusting screws, you need to achieve a systematic set of revolutions by the engine, so you should first let it run at low speeds. The deviation from the norm is the movement of the chain along the tire. In this case, the end screws must be adjusted to the optimal position so that the chain remains stationary.
- Transition to average speed. Sometimes the engine will smoke. This defect can be eliminated by tightening the screw to supply a leaner fuel mixture.
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What you need to have to set up and adjust a chainsaw with your own hands
Every carburetor owner should have the necessary tools to adjust this system. There are three adjusting screws located on the body of the device. They have their own markings:
- L. Screw for low rpm correction.
- H. Screw for high speed adjustment.
- T. Regulates the idle speed, in most cases it is used for experiments.
Before adjusting the carburetor, you need to prepare the device:
- The engine warms up, that is, it starts about 10 minutes before the repair, and turns off when you start work (see how to start the chainsaw).
- The air filter is checked and washed.
- The chain is stopped by turning the screw T as far as it will go (see chain oil).
To carry out a safe repair, you need to prepare a flat surface where you can carefully position the device, and turn the chain in the opposite direction. We need a tachometer. It determines the presence of a malfunction in the carburetor. When the screws are turning, the sound should be perfect and absolutely even. If squealing notes are noticed, then the mixture is oversaturated.
About the carburetor device
The carburetor serves to mix the combustible mixture with air, while observing the predetermined proportions. If the exact dosages are not followed, the correct operation of the engine is at risk. When a large amount of air enters during mixing of the components, and there is not enough fuel, then such a mixture is considered “poor”.
Over-saturation should also not be allowed, since with a large amount of fuel compared to air, malfunctions or engine wear are also possible. Carburetor adjustment is necessary not only before initial use, but also when any abnormalities in its operation are detected. Before starting work with the chainsaw, do not forget to run it in.
The carburetor design contains a standard set of elements, but it may vary slightly depending on the manufacturer. Components:
- The basis. It is a special tube that visually resembles an aerodynamic structure. Air passes through it. In the transverse direction in the middle of the pipe there is a damper. Its position can be changed. The more it is pushed into the passage, the less air enters the engine.
- Diffuser. This is the tapered part of the tube. With its help, the air flow rate increases exactly in the segment from which the fuel comes out.
- Channels for fuel supply. The fuel mixture is contained in the float chamber, then passes into the nozzle, from which it flows into the sprayer.
- Float chamber. It is a separate structural element, reminiscent of the shape of a tank. Designed to constantly maintain the optimal level of the fuel fluid in front of the inlet to the air channel.
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Design and principle of operation
A carburetor is a device in which fuel (gasoline) and air are mixed in predetermined proportions, followed by feeding the prepared mixture into the engine cylinder. Almost all models of chainsaws are equipped with carburetors of the same type, so the device and principle of operation are the same.
The main structural elements of the carburetor are:
- Body, which is cast from aluminum to reduce weight. Chainsaws constantly have to be moved from place to place, during operation they are held by hands, therefore, reducing the weight of the tool is the primary task of manufacturers;
- Diffuser with an air damper, which are located at the entrance;
- Jets, which are valves for metering fuel supply;
- Spray, providing gasoline injection into the chamber (in the diagrams it is designated as the main jet);
- Fuel (float) chamber.
Figure 1. Chainsaw carburetor diagram
The principle of the carburetor can be described as a cycle consisting of the following steps:
- When starting the engine, the choke opens.
- The piston stroke creates a vacuum in the air channel, as a result of which air enters the diffuser, the amount of which is regulated by the position of the air damper.
- Gasoline flows from the gas tank into the float (fuel) chamber. The rate of its entry is regulated by jets.
- In the diffuser, gasoline and air are mixed, resulting in the formation of a fuel-air mixture, which then enters the engine cylinder. The more mixture enters the combustion chamber of the cylinder, the higher the power and speed on the engine shaft will be.
To tune the carburetor, you will need a Phillips or slotted screwdriver of different lengths or thicknesses; the size depends on the design of this unit and the features of the engine assembly. It should be noted that some manufacturers make carburetors designed to use special tools.
In particular, special types of screwdrivers may be required to tune Husqvarna carburettors and other imported tools. It is advisable to clarify this question even when buying a chainsaw, so that you can purchase the necessary additional equipment in advance.
In addition, you will need refined gasoline or acetone to flush and clean the device. They are used to clean the outer surfaces of the carburetor. All internal channels are flushed with kerosene, diesel fuel or white spirit. Before flushing, the carburetor is disassembled, all rubber or plastic parts that may suffer from contact with aggressive chemical compounds are removed.
Open-end or spanner wrenches are used to disassemble the carburetor. Internal canals are flushed in specially designated trays, sometimes plastic syringes are used for this.
How to properly adjust the carburetor on a chainsaw with your own hands?
A chainsaw is a useful, and sometimes just a necessary tool for the owner of a private house. It has a high degree of autonomy, can be used in the field, where there is no possibility of connecting to the power supply network. For some craftsmen, the chainsaw is one of the main devices that perform large amounts of work almost daily. Such loads overwhelm the factory settings that were set for all important engine components.
The mode of operation most often changes at the carburetor, which has to be re-adjusted. Without understanding the design and principle of operation of this element, it is impossible to properly adjust it. The question concerns many users who closely operate chainsaws, so it will be useful to consider it more closely.
- Design and principle of operation
- When is carburetor adjustment necessary?
- Adjustment tools
- How to properly adjust the carburetor with your own hands?
- How to set up a China saw?
How to properly adjust the carburetor with your own hands?
After rinsing and completely cleaning the carburetor, assemble it and start adjusting. First of all, you should understand the purpose of the adjusting screws. The instruction will help with this, but some general points should be considered right away. The most common designations for screws are:
- H. Adjusts the state of the main jet, i.E. Adjusts the maximum speed of rotation of the motor shaft;
- L. Adjusts the idle jets (responsible for the minimum shaft rotation speed);
- T. Regulates the engine idling. It can also be designated by the letters LA or S, on some models of carburetors it is not at all.
Turning screws H and L clockwise depletes the fuel-air mixture, and counterclockwise enriches it (the amount of gasoline increases). When the screw T rotates, the idling speed of the shaft changes. It increases clockwise, and decreases in the opposite direction.
Figure 2. Carburetor adjustment mechanisms
Before proceeding with direct actions, you should find and carefully study the information on the position of the adjusting screws (the value of the angles of rotation when adjusting). This information is available in the instructions for the chainsaw. Then you need to prepare the workplace. Lay the saw on a flat horizontal plane, directing the chain in the opposite direction from you. Detach all covers, remove foam rubber and air filter. At this, the preparatory operations are considered completed, you can proceed to the main part of the work.
Carburetor adjustment procedure:
- Tighten the screws H and L clockwise with a smooth motion clockwise. Be careful not to break the screws. This will cause the complete loss of the carburetor.
- Unscrew both screws one and a half turns.
- Run the engine for 10 minutes and warm it up. This is a necessary moment, since it will not be possible to correctly adjust the carburetor on a cold engine.
- Turning screws H and L, alternately adjust the rotation of the shaft at maximum and minimum revolutions.
- By adjusting the position of the screw T (or it may have another designation), the idle speed of the chainsaw is adjusted. It is necessary to achieve smooth and stable engine operation. It is important to monitor whether the chain is idling or not. If it moves, turn the screw a little more counterclockwise.
You can check the operation of the engine visually and by ear. Too rich mixture will cause thick smoke from the exhaust. When the lean mixture is being fed, a whistling sound is heard while the saw is running. Excessive economy mode is harmful. If the L screw is set to “lean” fuel, there will be problems with starting the engine. If the H screw is set to lean, the saw will noticeably lose power. You can determine the correct setting by the following criteria:
- At idle speed, the engine does not stall, and the chain is stationary;
- There is no excessive smoke from the exhaust pipe while the engine is running;
- The engine demonstrates good throttle response (picks up speed quickly when you press the accelerator).
A detailed description of the setting is available in the instructions that come with the instrument in the delivery set. It should be carefully studied, as there may be some features or specific requirements established by the manufacturer and related only to this saw model. If all requirements are met exactly, the performance of the chainsaw will be restored to its original state.
When is carburetor adjustment necessary?
Initially, from the moment the tool was sold, all carburettors were adjusted and tuned at the factory. However, in the process of operation, the settings gradually get lost, and the operating mode changes in accordance with the operating conditions. Signs of a carburetor malfunction may include:
- Too high gasoline consumption, thick smoke comes from the exhaust pipe;
- Engine power is clearly not enough to perform normal tasks;
- Engine speed “float”;
- After starting, the motor stalls either immediately or after a few seconds;
- The engine cannot be started at all;
- The chainsaw “shoots”, there are sharp claps in the tool engine.
It should be noted that during the running-in of a new engine, the carburetor is set to a reduced fuel supply in order to limit the engine power. After the end of the run-in, the fuel supply increases to the nominal value. These adjustments are made using the adjusting screws on the carburetor body (there are usually two or three).
How to set up a China saw?
The design of the carburetor on Chinese chainsaws is not fundamentally different. The order and principle of adjustment also do not differ and are performed in the same order. The only difficulty that may arise during work is determining the purpose of the adjusting screws. Typically the T screw is at the top and the H and L are at the bottom of the carburetor body. One additional screw may be present.
Figure 3. Location of adjusting mechanisms
Usually, their purpose is determined empirically, slightly changing the position and monitoring the result. Once the purpose of the elements has been clearly defined, further customization is not difficult and is performed in the usual manner.
Chainsaw carburetor tuning is an important and necessary procedure that must be periodically performed to restore the normal operation of the tool. This process does not create fundamental complexity, but it requires the user to be careful, attentive and comply with safety rules. The chain of a chainsaw is usually not removed, since you will need to observe its position. Therefore, it is important to constantly remember about the possibility of launching it and exercise the necessary caution.
The adjustment should be done smoothly, with small changes in the position of the screws, so as not to cause too sharp changes in the shaft rotation mode. The result depends on the care and thoroughness of the user, and a properly tuned carburetor will extend the life of the tool.
The factory default setting for the Husqvarna carburetor is the position of the screws (H) and (L), in which a working chain saw is guaranteed to start. For Husqvarna tools, this is one and a half turns from fully tightened screws (H) and (L). In the process of adjustment, you must first set the screws to the standard position, then start the chainsaw and make precise adjustments to the power, the number of maximum revolutions and idle speed.
Tools required for work
Before proceeding with the tuning of the Husqvarna carburetor, you need to take care of having all the tools that may come in handy. To carry out this type of work yourself, you will need:
DIY carburetor repair
If in the course of carrying out a complete diagnosis of the Husqvarna chainsaw, carburetor defects were found, then some of them can be repaired without contacting a Husqvarna AB service center. For example, you can independently:
- Change the gaskets under the covers of the main chamber and the fuel pump;
- Clean or replace the mesh filter;
- Replace the diaphragm or needle valve of the main chamber;
- Troubleshoot the fuel pump diaphragm.
Gaskets, diaphragms and a rocker needle valve can be found in the repair kit that is available for each Husqvarna chainsaw carburetor model.
Also, if you have some experience, you can try to restore a faulty injector valve, but you cannot guarantee a positive result when trying to restore an injector, if it is faulty, manufacturers recommend changing the carburetor completely.
The first thing to do before removing the carburetor from Husqvarna is to clean the saw with a compressor, since dirt can interfere with a quality repair. Next, you need to open the top cover of the chainsaw, remove the air filter, disconnect the rods from the control levers of the air and throttle valves. Then unscrew the screws securing the carburetor.
It is quite easy to disassemble the carburetor body for repair. The main chamber cover is held in place by four screws that can be removed with a regular screw, the fuel pump cover is secured with one wide screw.
Below is a look at which it will become clear exactly how you can repair the carburetor without contacting a Husqvarna service center.
The structure and principle of operation of the Husqvarna carburetor
To successfully tune your Husqvarna chainsaw carburetor, you need to know its design and understand how it works. In fact, everything is not as complicated as it seems at first glance.
The saw carburetor has a built-in fuel pump, which is responsible for transporting a mixture of gasoline and oil, as well as a diaphragm, a needle valve with a rocker arm. Their joint work allows metering the fuel supply to the main chamber and two dampers.
One of the valves is designed to adjust the fuel supply to the cylinder when the gas is pressed, it is called the throttle, the second is responsible for restricting the air supply from the air filter to facilitate starting a cold Husqvarna chainsaw. At the moment when the operator cuts off the air supply to the carburetor with the help of the air damper, the fuel mixture becomes leaner and its supply to the cylinder increases, due to which the chainsaw starts much easier than in the case when a cold start is carried out in normal mode.
In the operation of the Husqvarna carburetor, a nozzle valve is involved, which atomizes the fuel and prevents air from entering the main chamber. Often, problems with saw operation can be caused by defects in this particular element. For example, a valve, if the chainsaw is not stored properly, may stick, the fuel supply will stop, which will make the engine impossible to operate. Also, irregularities in the operation of the injector can cause air to leak into the main fuel chamber of the carburetor. In such cases, adjusting the position of the adjusting screws will not correct the situation; repair or replacement of the unit will be required.
Three adjusting screws installed in the carburetor body are responsible for setting the quality and quantity of the mixture, as well as the number of revolutions of the crankshaft in idle mode:
- Screw (L). Adjusts the amount of fuel in the low and medium speed modes;
- (H). Responsible for traction at high speeds and their number;
- (T). Changes the position of the throttle valve, thereby regulating the amount of fuel mixture entering the cylinder and the operation of the engine of the tool in idle mode.
When does the carburetor of a Husqvarna chainsaw need adjustment?
There are a lot of problems that can be solved by adjusting the carburetor. Adjusting the carburetor of a Husqvarna chainsaw is necessary when such malfunctions appear:
- Increased idle speed;
- Strong smoke when operating the tool;
- Difficulty starting a cold or hot engine;
- Lack of traction and reduced maximum speed.
This is by no means a complete list of problems that can be solved by tuning the Husqvarna carburetor. In some cases, the quality and quantity of the fuel mixture is adjusted after an overhaul of the engine or in the process of scheduled maintenance of the chainsaw.
Adjusting the carburetor of your Husqvarna chainsaw
Modern chainsaws have a complex system and consist of several main units that periodically require maintenance and adjustment. In this article, we’ll talk about how to adjust the carburetor on your Husqvarna chainsaw.