Disassembling The Carburetor Lawn Mowers

What is the primary adjustment for??

Disassembling The Carburetor Lawn Mowers

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.

When starting the saw for the first time, it should work in a gentle mode. 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.

Simple rules will help to insure against malfunctioning of the chainsaw carburetor:

    Always mix gasoline and oil in accordance with the manufacturer’s numbers.

The proportions of the fuel mixture for the chainsaw engine

The chainsaw must start correctly, ensure 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 run-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.

How to recognize carburetor malfunctions?

Chainsaw carburetor operation diagram

Carburetor settings can be affected by:

    Lack of fixation of the adjusting screws;

Chainsaw adjusting screws

New CPG chainsaw Husqvarna 365

Chainsaw air filter with nylon insert

If any problems are found, they should be rectified immediately. But how do you know if it’s a carburetor? To do this, watch how your tool works.

Typical signs that carburetor settings are lost include:

  • Unstable motor operation

As a rule, the reason for this is the use of the wrong (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. Oversaturated mixture.

Carburetor set correctly. saw starts the first time

  • Arbitrary changes in engine power

May be due to 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, so adjusting the carburetor will postpone the overhaul only for a while.

  • Sneezing and jerking of the engine

This picture is observed when the carburetor channels are clogged or its filters are malfunctioning. In this case, adjustment should be carried out only 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 constructive node diagram and healthy logic.

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Chainsaw carburetor being repaired

DIY disassembly: nothing complicated

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

Removing the fuel hose and drive rod

Removing the throttle cable

After removing the gasoline hose, the carburetor is ready for disassembly.

Disassembly of the carburetor must be performed 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.

Dismantling the chainsaw carburetor in the photo

After disassembly, you need to troubleshoot and replace damaged or worn parts. Then the whole 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 the formations on their inner surfaces, they must be sonicated beforehand.

DIY chainsaw carburetor repair instructions

A chainsaw is needed in construction, gardening, and 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.

How does a chainsaw carburetor work??

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:

  • The basis

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

  • Diffuser

This part is where the warp tube tapers off. this is where the airflow rate rises, i.E. Air is always supplied to the carburetor under some pressure.

  • Spray

In this area, the fuel comes into contact with the air flow. 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.
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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 enters the carburetor, and the number of engine revolutions increases.

Candle cleaning

In the worst times of trimming with an unadjusted carburetor, the engine would stop starting after every tank of fuel was used. And only after cleaning the spark plug from carbon deposits could work continue.

Fine sandpaper was used to clean the electrodes, and to clean the space between the insulator and the housing. A thin paper clip with a folded end. First, the electrodes were wiped off large dirt with a rag, then they were cleaned with sandpaper. After that, the candle was dipped into diesel fuel and the moistened carbon was scraped off with a paper clip from the surfaces of the insulator, the inside of the body and between them. Further, the candle was dipped several times into diesel fuel, which was then shaken off it along with the dirt. Sometimes the paper clip cleaning and rinsing procedure was repeated. After that, the candle was wiped dry and was ready for further use.

Incredibly, one tank of fuel mixture with an unadjusted carburetor can be used up in less than 10 minutes. Tested in practice when the trimmer was started and operated at high rpm with maximum fuel supply (the adjusting screw was unscrewed much more than normal).

Other articles on this topic: Lubricating the Shaft of Lawn Mowers, Trimmers

From personal experience. Related publications. Spring may interfere

My first attempt to adjust the carburetor of the lawn mowers did not work, as the spring of the fuel adjustment screw interfered with. The factory spring turned out to be too thick when compressed and did not make it possible to reduce the fuel supply to the required level. I had to pick up another spring and continue adjusting after replacing it.

Fuel mixture adjusting screw with spring

In the photo above the factory spring, below the adjusting screw with the selected spring. I am writing about this because I’m not sure if this is an isolated case, and someone else may encounter the same situation.

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DIY lawn mowers carburetor adjustment

Regardless of the garden tool model, adjusting the carburetor trimmer requires careful preparation. The lawn mower owner will need to check the spark plug, air filter, and carburetor itself. In case of contamination, all elements must be cleaned, or, if necessary, replaced.

The trimmer comes standard with 3 adjusting bolts. The first of them is marked with the letter L, and is used to tune the engine when it is running at low speeds. The second bolt is marked with the letter H, and is required to adjust the internal combustion engine when it is operating at maximum speed. The third bolt can be labeled T or LA to allow the operator to set the engine to idle.

The process for setting up a lawn mower carburetor is as follows:

  • First you need to carry out a series of actions with the adjusting bolt L. To do this, turn it clockwise until it stops. After that, bolt L will need to be turned half a turn in the opposite direction. This will make it possible to adjust the optimal enrichment of the fuel mixture with oxygen when the engine is running at low speeds;
  • Then you will need to adjust the operation of the internal combustion engine in idle mode. To do this, turn the bolt T alternately in different directions until the mowing head or knife stops turning;
  • In the end, you will need to adjust the level of fuel enrichment with oxygen when the engine is running at maximum speed. To do this, bolt H will need to be turned clockwise until it stops, then return it 1/2 turn in the opposite direction.

Finally, the operator should stop the trimmer motor and start it again. If the unit has been configured correctly, the lawn mower engine will confidently pick up speed when the gas trigger is pulled, and quickly reset when the trigger is released.

Maximum speed limitation

After adjusting the fuel mixture and low speed, check how the lawn mower engine will run at maximum speed. If necessary, limit the maximum RPM to the required level with the # 3 hollow screw. Loosen the retaining nut and turn in the screw to decrease maximum RPM or turn to increase it. Tighten the nut after adjustment. The maximum RPM setting is necessary to protect the trimmer motor from overheating and to be able to use the start key lock to reduce right hand fatigue.

In the future, it may be necessary to adjust the trimmer carburetor. For example, if the engine starts to rev poorly when running at full load, loosen screw # 1 another quarter turn. If starting is difficult, increase idle speed. Both weather conditions and the quality of the fuel mixture can affect the operation of lawn mowers. Vibration can cause the adjusting screws themselves to turn.