DIY Chinese chainsaw carburetor repair

In detail: do-it-yourself repair of a Chinese chainsaw carburetor from a real master for the site my.housecope.com.

The functioning of the internal combustion engine (ICE) of a chainsaw is based on the combustion of a 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 - a 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 not understanding the principle of operation of this module, it will be problematic to correctly configure it.

The chainsaw carburetor consists of the following main nodes:

one-piece body made of lightweight 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 carburetor firm Walbro, which are 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 with needles (cones) at their ends. The screws have a right-hand thread, that is, they are screwed in a clockwise direction.

Chainsaw carburetor operation happens 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 the gasoline. The latter enters through the nozzles (15) and (12), and the air purified by the air filter through the damper (7) located at the diffuser inlet.
A damper (8), located behind 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.
The needle valve (11) determines 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 supply of the fuel mixture to the combustion chamber, and this depends on the number of revolutions of the internal combustion engine. Gasoline is cleaned through a filter (6).

Video (click to play).

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, it will be necessary to again make a more accurate adjustment of the supply of the combustible mixture.

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 has worn out - in this case, adjusting the carburetor of the chainsaw is possible as a temporary measure;
the engine does not function at idle;
increased gasoline consumption, due to which the unit emits a lot of smoke, the muffler and spark plugs become dirty with carbon deposits, and the engine power decreases.

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

cleaning filters (gasoline and air) are not contaminated;
the jets and the channels that fit them are clean;
membranes are not damaged;
the needle valve is serviceable and the required volume of the fuel mixture enters the float chamber.

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

Before adjustment, if possible, you should warm up the engine at idle or minimum speed for about 10-15 minutes.
By turning the “L” knob 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. When pressing the throttle lever, acceleration should go quickly and evenly. If a "dip" of revolutions is detected, the screw should be slightly unscrewed until this phenomenon is eliminated, since it is caused by insufficient enrichment of the fuel mixture.
When the mixture supply at low speeds is adjusted, you should start tighten 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.

The screw “H” compensates for the underestimated or overestimated speed due to the change of the type of fuel, the change in the concentration of oil or the humidity of the ambient air.

Also, the “upper” setting can fail if the low speed is incorrectly adjusted with the corresponding screw.

Screw “H”, not having enough experience, is better do not 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 speeds if the person who will perform the tuning has the knowledge and skills in adjusting 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” until, at maximum throttle, the engine develops about 15 thousand revolutions per minute (according to the tachometer) or the value 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%.

Read also: Kenwood 700w DIY repair

If it is supplied under low pressure, the problem is that the filter is exactly.

In this case, you need to clean the filter. It goes right through the tank. The filter is cleaned and returned back. It is washed under running clean water.

After that, the filter is dried and carefully put back. To prevent such a malfunction in the future, the filter should be cleaned periodically.

If cleaning the filter does not work well, then you should look for a respite. A clogged hole will result in insufficient air flow to the carburetor.

If the chainsaw is used frequently, muffler malfunctions may occur. This is very easy to spot.

If the tool is operating normally and when the speed increases, it starts to stall, then the spark arrester is the cause.

Most often, this element fails as a result of contamination with combustion waste. You can easily solve this problem with your own hands.

First of all, you need to remove the muffler and disassemble it. It should be borne in mind here that in some models spark arresters are not understood. After that, the muffler is cleaned of carbon. To do this, use special detergents.

When the deposit is removed, the spark arrestor is dried with a hair dryer. At the final stage, the muffler is installed in place.

As for the carburetor, adjustments and repairs can be done at home. But in order to perform such work with high quality, it is necessary to know the structure of the carburetor and the principle of its repair.

Poor repairs can cause serious damage to the device. Therefore, experts recommend that adjustments and repairs be carried out in specialized workshops.

As you can see, many chainsaw problems can be fixed with your own hands. But for this you need certain information. If you are unsure of your abilities, it is better to seek professional help.

Watch a video in which a specialist shows in detail the dismantling-assembly process for repair with his own 142:

A chainsaw is needed in construction, and in gardening, and in landscaping - its presence greatly simplifies the implementation of a number of tasks for processing wood. The main unit of this tool is the engine, the operation of which largely depends on the state and settings of the carburetor. This is where the fuel mixture is prepared. This means that if the saw does not start, stalls or does not provide the required power, it is likely that the reason for this is improper operation of the carburetor. Fortunately, you can handle this yourself in many cases. Only for this you need to know and understand the device and principle of operation of this unit and, of course, the chainsaw itself.

The main purpose of the carburetor is to mix fuel with air in the required proportions. If the latter are violated, this is almost instantly reflected in the operation of the engine.

Stihl MS 181 C BE chainsaw carburetor

Chainsaw carburetors may vary in design. However, their basic elements and the principle of operation remain approximately the same.

Carburetor device:

This is a wind tunnel, across which the air damper is located - with its help the intensity of the air supply is regulated.

This part is located where the base tube is narrowed - here the air flow rate increases, i.e. air is always supplied to the carburetor under some pressure.

In this area, the fuel comes into contact with the air stream. Fuel enters the atomizer from the float chamber through the nozzle (metering device).

Float chamber

This is a container that allows you to keep the fuel mixture in a stable state.

Structural diagram of a chainsaw carburetor

The chainsaw carburetor works according to the following principle:

when the engine is started, the main flap opens and a stream of air is supplied into the air channel at a certain speed;
the air flow rate, as well as the level of the float in the chamber, are regulated by the position of the damper, namely, due to the difference in pressure in the float chamber and the air channel;
the fuel from the float chamber is sucked into the nozzle, and from there into the diffuser;
passing through the diffuser, the air captures the fuel entering there;
the resulting mixture is fed into the cylinder chambers through the inlet channels.

The principle of operation of the chainsaw carburetor

The pressure in the float chamber is approximately equal to atmospheric, but in the air channels of the carburetor, when the engine of the chainsaw is started, a vacuum occurs. Opening the damper increases the air flow rate. As a result, more fuel flows into the carburetor, and the number of revolutions of the engine shaft increases.

In the first hours of operation, the 2-stroke engine of the chainsaw requires running-in, on which the quality of its further work depends. During the running-in process, the primary adjustment of the carburetor is performed - the optimal parameters for the preparation and supply of the fuel mixture are set.

Chainsaw initial break-in: working with thin material

Most modern chainsaws are sold adjusted. Nevertheless, the quality of the factory settings does not interfere with checking - in the end, you will have to work with the instrument.

The first time you start the chainsaw, it must be gentle. Therefore, for several hours after the start, it is recommended not to overload the engine and only cut small branches and trunks up to 10 cm thick.

To insure against malfunctions in the carburetor of the chainsaw, simple rules will help:

Always mix gasoline and oil in accordance with the manufacturer's numbers. The proportions of the fuel mixture for the chainsaw engine
Do not prepare the fuel mixture in advance - the properties of gasoline and oil when mixed will lose over time. An exception is fuel for an intensively used tool, however, here, one should not exceed the approximately weekly rate.
Use the oil specified for your chainsaw engine. A fuel mixture with a non-standard composition will disable it seriously and for a long time.
When preparing the fuel mixture, take into account the influence of climatic conditions on its components.

The chainsaw must start correctly, provide a stable sprocket speed and smooth power increase / decrease. When the engine is running, there should be no extraneous knocks, pops and noises.

Professional hand-held chainsaw at work

The main thing during the initial running-in of the tool is to ensure that the fuel consumption corresponds to the power used, i.e. in practice, the saw should not go out, "sneeze", smoke and work in jerks.

Typical carburetor malfunctions are easy to recognize. They are expressed in the fact that the engine of the chainsaw starts up and immediately stalls or does not show signs of life at all. Well, or it consumes fuel with might and main, producing clouds of black smoke and aggressive vibrations instead of the required power.

Chainsaw carburetor operation diagram

Carburetor settings can be affected by:

lack of fixing the adjusting screws; Chainsaw adjusting screws
wear of the piston group; New CPG chainsaw Husqvarna 365
blockage of the fuel-air channels;
damage to air filters; Chainsaw air filter with nylon insert

If any problems are found, they should be rectified immediately. But how do you know if the carburetor is the problem? To do this, watch how your tool works.

Typical signs that carburetor settings are out of order include:

Unstable motor operation

As a rule, the reason for this is the use of an incorrect (lean) fuel mixture.

Excessive consumption of fuel

It is expressed in an increased emission of waste exhaust, which turns black. This means that the fuel is not completely consumed, i.e. the mixture is oversaturated.

Carburetor set correctly - saw starts the first time

Arbitrary changes in engine power

May be associated with damage to the fastening of the adjusting screws or the protective cap.

Increased fuel consumption accompanied by vibrations and pops

It speaks of critical wear of the piston group, therefore, adjusting the carburetor will postpone the overhaul only for a while.

"Sneezing" and engine jerking

This picture is observed when the carburetor channels are clogged or its filters are malfunctioning. In this case, adjustments should only be made after thorough flushing of the assembly.

Chainsaw fuel filter

Despite the fact that the carburetor is the most difficult part of the engine, you should not be upset if it detects malfunctions in its operation. Instead, you need to arm yourself with some tool, a knot design, and some healthy logic.

Chainsaw carburetor being repaired

First of all, you need to prepare a place for disassembly. This can be a workbench or a regular table. In addition, you need a rectangular piece of cloth or cardboard - on it you will neatly fold the carburetor parts. And, finally, a tool: for disassembly, you will need a set of open-end wrenches and screwdrivers, a special cleaning compound and an ultrasonic cavitation bath.

Chainsaw carburetor repair tool

First, you have to dismantle the chainsaw carburetor. This is done in this order:

To get to the carburetor, you need to remove the top cover of the chainsaw, which is fixed with three bolts. Removing the carburetor cover
After removing the cover, do not forget to remove the gasket, which is an integral part of the air filter, and the body of the latter, for which you need to unscrew the corresponding nuts and / or remove it from the clips.
On the right side of the carburetor there is a fuel hose; it must be removed together with the air damper drive rod, not forgetting to pull it off the fitting on the left. Removing the fuel hose and drive rod
After removing the hose and rod, remove the throttle cable tip from the fixing socket and finally dismantle the gasoline hose. Removing the throttle cable
The carburetor can then be removed from the mountings for later disassembly. After removing the gasoline hose, the carburetor is ready for disassembly.

Disassembly of the carburetor must be carried out in the manner prescribed by the design and functional solutions of its elements. Chainsaw carburetor parts do not differ in size, so they need to be folded carefully and in order, trying not to lose anything.

After disassembly, it is necessary to carry out troubleshooting and replace damaged or worn parts. Next, the entire set should be rinsed with a special product, dried and wiped with a dry, lint-free cloth. The jets and tubes of the assembly must be blown out with compressed air, or, in order to more thoroughly remove formations on their inner surfaces, they must be treated with ultrasound before that.

Reassembly of the carburetor is carried out only after complete cleaning, drying and blowing with compressed air. At the same time, do not forget that some gaskets and seals, even if they are not damaged, must be replaced.

You can start adjusting the carburetor provided it is correctly troubleshooting, high-quality assembly and flawless re-installation on the engine.

Carburetor setting principles:

screws H and L adjust the ratio of air and combustible mixture, i.e. throttle position. Tightening the screws clockwise leads to a depletion of the mixture and the transition of the engine to low revs. When unscrewing (counterclockwise), the mixture is enriched, and the engine speed increases;
screw T is responsible for adjusting the idle speed: turning it clockwise gives an increase in their number, against - a decrease;
screws are adjusted in L-H-T order. Chainsaw Carburetor Calibration

The general adjustment algorithm looks like this:

Initially, the highest idle speed is found by turning the screw L and then returning it by ¼ turn counterclockwise. If the chain rotates at idle speed, turn the screw T in the same direction until it comes to a complete stop.
With the engine warm, running at full speed, turn the screw H by ¼ of a turn to the left, then let the engine run for 10 s to check the maximum speed using a tachometer. It must correspond to the number indicated in the instrument's passport.
After the calibration with screws L and H, the idle speed is adjusted with screw T. If done correctly, the engine will run evenly in all positions. Memo for calibrating the carburetor on the body of the chainsaw

Upon completion of the adjustment, it remains to reinstall the cover of the chainsaw with an insulating gasket, after which you can start the main work. If the settings are correct, the chainsaw engine will get the optimal fuel mixture. This will ensure its normal efficiency, as well as the overall comfort and safety of working with the tool.

Installing a chainsaw carburetor. Or how not to pay repairmen! Image - DIY Chinese chainsaw carburetor repair

Using a chainsaw makes life much easier even for an amateur, and in some professions this tool is almost indispensable. However, like any relatively complex device, a chainsaw requires periodic maintenance. Due to untimely or inadequate maintenance and due to the impact of both planned and excessive loads, various malfunctions can occur. For professionals, interruptions or erratic saw operation will reduce work efficiency or may result in a ruined work day. One of the most common malfunctions is the improper tuning of the chainsaw carburetor, which gets confused due to unsuccessful attempts to adjust or switch the adjusting screws for other reasons.

The following symptoms and malfunctions indicate the need for carburetor adjustment:

the engine starts with deformation and stops almost instantly;
gasoline consumption is too high, the exhaust is too thick, the combustible mixture in the cylinder does not completely burn out;
the factory settings of the chainsaw carburetor were knocked down (due to vibrations or unsuccessful attempts to adjust);
malfunction of the air purification system, which led to the ingress of debris particles into the fuel distribution mechanism;
significant wear of the piston group - the carburetor setting in this case acts as a temporary measure.

It is clear that when dirt enters the fuel system with one set, the problem cannot be solved - flushing is necessary. In the event of a worn piston, a major overhaul is required. However, in all these cases carburetor also configured.

A carburetor is required to prepare the air / fuel mixture for engine power. If the proportions in this mixture are not correct, engine operation is interrupted. If proportions to an increase in the amount of fuel are not observed, the mixture is said to be oversaturated if the fuel, on the other hand, is unlikely. At work, the engine is neither the best way.

In different models of chainsaws, carburetors differ in design, but they are, in principle, similar to the action. The air flow moves at high speed through the air channel. A damper blocking the channel allows you to vary the speed of the air blast. The fuel is fed through the nozzle 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 before mixing, is practically equal to atmospheric pressure. But the air duct creates a vacuum so that the fuel is drawn into the air stream. The more the flap is opened, the faster the air moves, and the amount of fuel also increases - the engine speed increases. Therefore, it is easy to imagine the principle of the carburetor.

For efficient, smooth operation of the tool, for maximum performance and at the same time economical fuel consumption, tuning the carburetor of the chainsaw is required. Fuel and air filters should be checked before adjusting to ensure they are clean. Most chainsaws are adjustable with three screws: idle, high speed, low speed. When the carburettor is set correctly, the following symbols indicate:

The chain does not move when idling.
The engine accelerates smoothly and quickly.
The sound of the engine running is smooth, similar to that of a four-stroke engine.

The video shows a simple yet effective way carburetor adjustment induction tachometer. Looks like.

Doesn't start Chinese chainsaw. Diagnostics and repair.Carburetor repair.Carburetor adjustment.

When adjusting the carburetor, you should handle with the utmost care, since errors in the settings can lead to very serious consequences, up to the occurrence of engine malfunction. If you are not absolutely sure of your abilities, contact the service center.

For start mode so that the parts are sufficiently lubricated, the Husqvarna chain carburetor is adjusted so that the maximum speed is 600-700 rpm. below working. If it is not possible to set the operating maximum frequency on the tachometer, there is no need to change the presetting with screw H. Exceeding the value of the maximum speed by the manufacturer is prohibited. If, after completing the adjustment with the engine idling, the saw chain moves by turning the screw T counterclockwise, causing it to come to a complete stop.