Tuning The Carburetor Of A Chinese Chainsaw

Checking acceleration work

A little research needs to be done. Device acceleration is initiated. The serviceability of the engine should be assessed during the maximum revolutions. When the engine is functioning correctly, then when you press the accelerator, the speed rises quickly to 15,000 rpm.

If this does not happen or the increase in speed is too slow, it is necessary to use the screw marked with the letter L. It turns counterclockwise. Moderate movements must be observed, since the turn cannot be more than 1/8 of a full circle.


In order for the chainsaw to work properly, you need to carefully perform work on adjusting the carburetor in exact coordination of their sequence. If there are any irregularities in the functioning of the device, it is necessary to completely disassemble it yourself. In most cases, it is necessary to replace any parts that have become unusable.

With constant checking of the quality of carburetor settings and taking timely actions to improve its operation, problems with the chainsaw do not arise.

About which chainsaw to choose. Read here.

Do-it-yourself chainsaw carburetor adjustment

The use of gasoline dust is widely used Not only in the professional forestry industry, but also in the household.

Indeed, the mobility and versatility of the tool allows a wide range of work to be carried out at a minimum cost.

A feature of gasoline dust engines is the required frequency of carburetor regulation.

The engine resource, and therefore the tool as a whole, depends on how correctly such a setting is performed.

The principle of operation of the carburetor is as follows:

Air enters the supply pipe at a certain speed, which is regulated by a damper.

When the tube is opened, the float chamber is activated.

The air flow is accelerated by the diffuser and mixed with the fuel coming from the float chamber.

The sprayer sends the prepared mixture into the inlet channel, through which it enters the cylinder.

Fuel suction is achieved by the pressure difference in the float chamber and the delivery pipe.

In this case, the engine speed is directly proportional to the amount of incoming fuel.

Adjusting the Chinese chainsaw. The main stage

The engine starts at medium speed and warms up for about 10 minutes. The screw responsible for adjusting the idle speed must move clockwise. It is released only when the engine comes into stable operation. It is necessary to check that the chain does NOT move during this process.

In idle mode, the engine may stall (reason. Here). In this case, immediately turn the adjusting screw clockwise until it stops. Sometimes the chain starts to move. In this case, turn the adjusting screw in the opposite direction.

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When adjustment is needed

As already mentioned, the new chainsaw already has standard fuel settings. But for proper break-in, it is recommended to limit the maximum engine speed, and this is done using the adjusting screws located on the carburetor body. Also, after running in, you will need to make a more accurate adjustment of the fuel mixture supply again.

In addition, you will have to adjust the carburetor in the following cases:

  • Due to strong vibration, the factory settings are lost;
  • The internal combustion engine does not start well and immediately stalls;
  • The internal combustion engine starts up, but the speed does NOT develop, and it stalls;
  • The piston group was worn out. In this case, adjusting the chainsaw carburetor is possible as a temporary measure;
  • The engine does NOT idle;
  • Increased gasoline consumption, due to which the unit emits a lot of smoke, the muffler and spark plugs become dirty with carbon deposits, the engine power decreases.

The design and principle of operation of the chainsaw carburetor

The chainsaw carburetor also consists of the following main components:

  • One-piece body made of light aluminum alloy;
  • A diffuser located at the entrance to the carburetor;
  • Nozzles, Special valves designed to regulate the supply of a combustible mixture;
  • Sprayer;
  • Float chamber.

Below is a diagram of a Walbro carburetor, which is very often equipped with chainsaws. Using this scheme, you can study in more detail the internal structure of the chainsaw carburetor.

The carburetor can have 2 or 3 adjusting screws with springs. The adjusting screws are designed so that there are needles (cones) at their ends. The screws have a right-hand thread, that is, they turn clockwise.

The work of the chainsaw carburetor is as follows.

  • After starting the internal combustion engine, the air damper opens.
  • In the diffuser (16), where there is a constriction, the air flow is accelerated and mixed with gasoline. The latter enters through the jets (15) and (12), and the air purified by an air filter. Through a damper (7) located at the diffuser inlet.
  • The damper (8), located along the diffuser, regulates how much of the prepared mixture enters the combustion chamber.
  • The volume of gasoline passing through the jets is regulated by screws (17) and (10). These are, respectively, screws L and H on the chainsaw.
  • Here the needle valve (11) depends on the volume of the fuel mixture in the float chamber (14). The functioning of the needle valve is controlled by a diaphragm (13).
  • The membrane (4) controls the flow of the fuel mixture into the combustion chamber, and this depends on the number of revolutions of the internal combustion engine. Gasoline is cleaned through a filter (6).

Setting up and troubleshooting a chainsaw carburetor

The functioning of the internal combustion engine (ICE) of the chainsaw is BASED on the combustion of the fuel-air-oil mixture. To mix the gasoline-oil mixture with air, and then feed it in portions into the combustion chamber, a rather complex device is installed on the engines. Carburetor. When buying a new chainsaw, the carburetor already has factory settings, but over time they get lost, and the device that controls the fuel supply needs to be adjusted again. NOT knowing how the carburetor works, and I do not understand the principle of operation of this module, it will be problematic to correctly configure it.

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Carburetor tuning rules

You should be aware that the carburetor can only be adjusted correctly if:

Tuning The Carburetor Of A Chinese Chainsaw
  • Cleaning filters (petrol and air) are not dirty;
  • The jets and the ducts connected to them are clean;
  • The membranes are not damaged;
  • The needle valve is operational and the required volume of the fuel mixture is supplied to the float chamber.

To adjust the carburetor of imported chainsaws, you must adhere to the following rules.

  • Before adjusting, if possible, warm up the engine at idle or minimum speed for about 10-15 minutes.
  • By turning the knob “L” they achieve such an engine operation so that it idling one and a half to two thousand revolutions per minute. But you should pay attention to how the engine picks up speed. Acceleration should go quickly and evenly with the acquired on the accelerator lever. Upon detection “failure” turns, the screw should be slightly Unscrewed to eliminate this phenomenon, since it is caused by insufficient enrichment of the fuel mixture.
  • When the mixture supply is adjusted at low speeds, you should start to tighten the screw “T” until you notice the saw chain turning. After that, the screw should be unscrewed by half or a third of a turn, observing the behavior of the clutch mechanism. Normally, the saw should not rotate at idle speed.

By screw “H” underestimated or overestimated revolutions are compensated for due to the change of the type of fuel, changes in oil concentration or humidity.

Screw “H, not having enough experience it is best NOT to regulate. If the tuning of the carburetor of the chainsaw is carried out by an incompetent person, there is a great danger that a too lean mixture will enter the combustion chamber at high speeds, especially under load. Such engine operation will inevitably lead to rapid wear of its piston system and to a failure in the ignition system.

It is possible to start adjusting high revs if the person who will perform the tuning has the knowledge and skills to adjust carburetor engines. The master-tuner must have a special device at his disposal. Tachometer or multimeter with oscilloscope function.

Setting up the carburetor of a chainsaw, namely, high engine speed, follows a simple scheme.

  • It is necessary to tighten or unscrew the screw “H” as long as, at maximum gas, the engine does NOT develop about 15 thousand revolutions per minute (according to the tachometer) or the value that is indicated in the manual for this unit.
  • When using an oscilloscope, the spark discharge frequency should be between 230 and 250 Hz. It should be borne in mind that under load, the frequency can decrease by approximately 10-15%.
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The carburetor of a Chinese chainsaw should be adjusted in the same way as described above. There are holes on its body, into which, in order to adjust the engine speed, you need to insert a flat screwdriver. Each hole is labeled with one of the three letters. As a rule, you can see the letter near the top hole “T”, and near the bottom (shown by arrows). Letters “L” and “H”.

The Chinese chainsaw Carver (CARVER) has the same arrangement of screws. The following figure shows what a Chinese chainsaw carburetor looks like outside the unit body.

How to troubleshoot a carburetor

The main malfunctions of the chainsaw carburetor may be as follows.

  • The engine starts with difficulty and stalls a few seconds after starting. This is often a prerequisite for an incorrect low speed setting. The fuel-air mixture is poorly enriched. Unscrew the screw “L” half a turn, after which the adjustment should be completed with a screw “T”.
  • The engine power is noticeably reduced under load. This means that the carburetor is over-oxygenating the mixture. Therefore the screw “H” you need to tighten it a little, about 1/8 of a turn. If, after such actions, the engine power is still insufficient, but there has been some improvement in its operation, then the regulator can be tightened a little more.
  • The engine starts at maximum speed and without load. “sing”. This malfunction of the unit is caused by a lean mixture and overestimated speed. Setting is done with the same screw “H”.
  • Gasoline does NOT enter the combustion chamber. Breakage can be caused by clogged fuel filter, carburetor passages and jets. To eliminate the malfunction, you need to completely disassemble this chainsaw module and purge its channels with compressed air (you need a compressor). To properly clean the fuel channels, you can use a special carburetor flushing fluid. Also, the lack of fuel flow into the engine cylinder may be due to improper adjustment. How to do it yourself, discussed above.
  • Overflows the carburetor. In 90% of cases, fuel overflow is caused by a dried and hardened membrane, which presses on the rocker arm associated with the needle. To change it, you will need to remove and disassemble the carburetor.
  • The engine picks up speed poorly, runs intermittently, and decreases power. These problems are often caused by a clogged air filter. It will be necessary to remove the cover that covers the filter and to clean it, which consists in washing with detergents.

In general, timely adjustment, as well as timely repair of the chainsaw carburetor, can significantly extend the life of the entire piston system of the engine. Therefore, the tuning of this component of the fuel system must be treated with great care.