properly, adjust, carburetor, chainsaw

Design and adjustment of a chainsaw carburetor

The carburetor is one of the most important components of any modern chainsaw. Its main task is to mix the fuel mixture with air, as well as to deliver the fuel to the gasoline engine cylinder. During the operation of the chainsaw its carburetor is constantly working, so, over time, this node begins to need adjustment and flushing. To perform these procedures is quite simple, if you are very attentive and observe the correct order of operations.

Almost all of the carburetors used in chainsaws have the same device. Only the mechanisms with which Chinese garden tools are equipped make the difference.

The standard fuel unit consists of the following parts:

  • Float chamber. this element is designed to continuously maintain the required quantity of fuel. When the node works, the fuel is transferred to the atomizer through the built-in nozzle;
  • the tube. fuel flows into the chamber in small portions through it. The fuel supply is regulated by the position of the built-in factory flap;
  • atomizer. this part is necessary for injecting fuel into the intake air flow.

The principle of operation of a chainsaw carburetor is quite simple. During the operation of the assembly, air is sucked in by a tube and passes through it at a rate that is regulated by the built-in flap. When the choke opens, the float in the chamber is actuated. After passing through the diffuser, the air is mixed with the fuel and atomized instantly. Then the air-enriched, high-quality fuel mixture passes through the intake port and into the engine cylinder. The diagram shows how the carburetor works.

Fuel circulates through the assembly under pressure. In the float chamber it is close to atmospheric pressure, but in the standard air intake pipe it is more rarefied. Due to the pressure differential, the fuel-air mixture enters. The higher the quantity of fuel, the higher rpm the chainsaw engine can create.

When adjustment is necessary?

often than not, owners of chainsaws from Husqvarne and other manufacturers don’t have to adjust the carburetor very often. To know that it is time to perform this operation, you should be guided by the following signs:

  • After starting the engine rather quickly stalls or it is impossible to start it at all. This is most often attributed to the use of a lean fuel mixture;
  • When the tool is running, more fuel is being consumed. Higher production of exhaust gases may also be observed. This generally occurs when an oversaturated mixture is used.

It should be noted that adjustment failure is quite rare, but it can occur in the following situations:

  • In the case of a breach in the fixing of the adjusting screws. This may be due to vibration or breakage of the protective cap. In principle, this is unlikely to happen if no one has touched them.
  • Severe engine wear, especially piston wear. In this case from the factory settings will be of little use. A temporary solution in such a situation may be to adjust the carburetor of the chainsaw. However, still do not expect that this will permanently solve the problem. After performing this operation, you need to be prepared for the fact that in the near future you will need to perform engine repairs.
  • You may also need to adjust the carburetor because of a clog in the carburetor. Use of poor-quality gasoline, a broken air filter, or scale formation could cause this. In these cases, a single adjustment is not enough. The carburettor needs to be disassembled and cleaned of dirt.

Other problems

Chainsaw will not start

Before you adjust the carburetor, find out what’s causing the problem. Consider the situations that may arise:


It’s understandable that before you do anything about the chainsaw, you need to understand why it’s not working properly.

First you need to take care of a comfortable place to make adjustments or repair the carburetor. It must be a level platform, wide enough so that the parts laid on it are not lost by falling to the floor.

There is water in gasoline

Water in petrol

Compared to water, gasoline has a lower density, so it will always be above the water in the tank. The chainsaw will not be able to work on such a composition, so you need to get rid of what should not be in the tank by draining the water.

To check if this is the case, you need to disconnect the fuel pipe from the carburetor and put it in a plastic bottle and drain the gasoline into it. As you can see in the photo. it will collect at the bottom. In such a case, the carburetor needs to be disassembled and cleaned. If there is no water in the fuel, then we return it to the tank and look for another malfunction.

Properties of gasoline deteriorates over time, and the engine can not start just for this reason. In this case, the old fuel is drained and fresh fuel is poured instead.

What to flush the carburetor of a chainsaw?

To clean the assembly of heavy contaminants, it is best to use a product that comes on sale in pressurized cylinders. Included with the cleaner is a dispenser and a long thin tube, which makes it possible to spray the product in any hard-to-reach places.

It must be remembered that cleaning the carburetor on the chainsaw is carried out with the use of flammable chemicals. Work with them must be in a special protective mask and only in well-ventilated rooms.

To clean the carburetor on a chainsaw, the assembly will need to be partially disassembled. Throttle, adjustment screws, carburetor body and other carburetor parts must be washed with a tool from a balloon and set aside to dry completely. As soon as all elements are dry, the assembly can be assembled and put back on the chainsaw.

Setting and Adjustment Features

To learn how to adjust the carburetor on the chainsaw, you should learn to distinguish the three screws (some models have only one).

L and H screws are only similar in appearance, in fact they are different

Each screw has its own letter designation:

  • “L” is used to adjust the low rpm;
  • “H” is necessary to adjust the upper revolutions;
  • “T” is needed to adjust the idle speed (models with a single screw have only one).

The factory setting is optimal, and the screws are used to adjust the engine’s performance in special situations (work related to different climatic conditions).

The diagram shows the outputs of the carburetor adjustment screws when the cover is closed

A special tool is used to adjust the chainsaw

Only use the L and H screws for adjustment. To increase the RPM, turn them clockwise. To lower. counterclockwise. The sequence in which the screws are used: L. H. T.

If there are any doubts about the adjustment, it is better to contact an expert, because wrong adjustment can lead to engine failure.

Adjusting the carburetor of a chainsaw with their own hands

Adjusting the chainsaw carburetor allows the tool to operate efficiently at full power with economical fuel consumption. Adjustment should be performed with a clean fuel and air filter. In case of more carburettors, adjustment is performed with three screws: for maximum and minimum rpm and idle speed adjustment.

Use the H and L screws to adjust the gasoline/air mixture ratio determined by the opening of the carburetor choke. Unscrewing the screws enriches the mixture and lowers rpm, tightening the screws weakens the mixture and the rpm increases.

The designation H refers to the maximum RPM screw that controls the main nozzle, L. Adjustment should be made with the minimum RPM screw that controls the idle speed restrictor. Use the S screw to precisely regulate idle speed. Sometimes, in order to simplify adjustment, the number of available adjustment screws of the carburetor is reduced.

Tuning of the chainsaw carburetor is divided into two steps. the basic (factory tuning), which is done with the engine turned off. and the final step, which is made with the engine running warm. The exact value of the rotation angles should be taken from the instruction manual for your particular chainsaw. Failure to follow the manufacturer’s instructions may result in damage to the motor.

turn the adjusting screws for the maximum H and minimum L RPM slowly clockwise as far as they will go and then turn them back two turns

Find the highest idling speed by slowly turning the screw L in different directions. After having found the position of maximum engine rpm turn the screw L a quarter of a turn anticlockwise. When the chain is idling, turn the screw T or (S) clockwise until it stops.

Checking and adjusting maximum rpm.

Change the maximum rpm with the H. When it is turned in (clockwise rotation), the rpm increases, when it is turned out, the rpm decreases. decreases. Chainsaw engines have the maximum rpm at 11500 rpm. up to 15000 rpm. A higher speed is not provided by the ignition, moreover, it becomes dangerous for the engine. It is possible to determine the RPM limit by looking at the ignition interruption. If so, turn the screw H slightly anticlockwise.

If you have not checked engine and peak rpm you should not consider the tuning of your chainsaw complete.

A smooth pull on the throttle trigger should allow the engine to quickly and surely climb from idle to maximum rpm (2,800 rpm or higher).up to 11500-15000 rpm depending on the machine). If they come on slowly, with a lag, turn the L screw slowly counter-clockwise, but not more than 1/8 turn.

After adjusting the acceleration and maximum rpm, check the idle speed again. the engine should run steadily, the chain should not move. The chainsaw must be tuned again if this condition is not met but except for the basic adjustment step.

When the chainsaw carburetor needs to be adjusted?

Here’s a list of the most common situations where you’ll need to tune your chainsaw’s carburetor:

  • The engine fires, but the chain saw stalls or fails to fire. High fuel consumption may be caused by too much air in the fuel chamber.
  • Excessive fuel consumption. This can be caused by excessive fuel saturation in the mixture that goes into the engine. The mix must be of good quality to keep the engine running smoothly.
  • The bolts in the carburetor have lost their hold due to a damaged carburetor housing.
  • Debris in the carburetor. This can happen if the filter is damaged or low-quality fuel is used. You will need to completely disassemble the carburetor, rinse it and readjust it.
  • The engine does not idle or does not develop full power.

Important! If the engine does not run well because the piston is worn, adjusting the carburetor will not work. In addition, along with tuning, it is desirable to clean the carburetor of debris. this will increase the effectiveness of the procedure.

properly, adjust, carburetor, chainsaw

Top tips for carburetor tuning on chain saw

When adjusting the carburettor of a chainsaw it is impossible to turn the rotary knob of low revolution even stronger than the rotary knob of high revolution. If you do not follow this rule there will be too much air in the combustible mixture. The consequence of this wrong tuning is dryness of the piston while running and overheating.

Before you adjust the carburetor, take note of the initial settings, so you can return to them in case the tool will not start or does not work properly.

Follow safety rules, do all the work with the engine turned off, with the battery stopped and with safety gloves on.

Regulation of chainsaws. not an easy, but feasible procedure. You can learn about it from the video, recommendations on adjustment of carburetor of concrete model.

If you do not have experience, technical regulations, accurate measuring instrument, it is better to trust the technical experts to adjust the settings. Store Start-Pro offers adjustment of the gasoline saw carburetor, you can also contact us if you need tensioning or grinding chain saw blade.

How To Tune A Chainsaw | Adjusting The Carburetor

Proper, professional adjustment of the carburetor is an easy start of the chainsaw engine, stable operation and long service life of the tool. Calling a specialized service, you will save time, nerves and money.

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properly, adjust, carburetor, chainsaw

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