Adjusting The Chainsaw Stihl 250 Carburetor.

For a small compact mechanism chainsaw, Stihl 250 correct setting of the carburetor plays a key role. All coordinated work, all load modes, and its trouble-free operation are directly dependent on the adjustment of fuel supply systems, the quality, and quantity of the fuel-air mixture. This article describes how to adjust the carburetor for the Stihl 250 and configure all its dosing systems.

Carburetor arrangement.

A modern carburetor for a chainsaw made in Germany “Stihl 250. It is a node the size of a half of a human fist. The manufacturer of the machine is the company Walbro, Taiwan. Body material. stainless steel alloy. A damper is fixed in the bottom of the device, which ensures a uniform supply of the fuel-air mixture to the engine’s combustion chamber.
There are holes for attaching the assembly to the body of the power unit. Between the flanges of the mixture and the combustion chamber of the engine installed the sealing gasket. Under the throttle rod is an acceleration pump. It is a small piston with a rubber ring.

At the front of the case there is a series of user-friendly spring-loaded adjustment screws:

  • idle move;
  • maximum speed;
  • amount of mixture;
  • quality mix.

Adjusting the carburetor chainsaw Stihl is made with these screws.
The main innovative feature of the carburetor for the Stihl 250 chainsaw is the heating device. To avoid freezing of the mechanism during operation during the winter period, it is equipped with a unique system that pre-heats the steel case during process. To do this, the unit is transferred to the winter mode of operation.
Heated air sucked from the engine blows the hull. Such a mode of operation of the mechanism prevents icing and freezing of the nozzles, ensures the normal flow of the fuel-air mixture. When switching to summer operation, the hot air flap closes. The natural cooling of the unit characterizes summer mode.

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The need for adjustment.

Throughout the process of operation, periodically, there is a need for additional adjustment and ensuring the correct supply of the fuel-air mixture. How to determine exactly when and what setting you need to perform for the normal functioning of technology? There are characteristic signs when the mechanism, according to the behavior of individual parts, itself prompts when adjustment is necessary.
First of all, each time before the next engine start, it is necessary to check the color of the spark plug electrodes.

By changing it, you can decide the need to adjust, adjust workflows, improve the quality of the combustible mixture:

  1. Black electrodes, covered with soot or carbon, indicate a re-enriched air-fuel mixture entering the engine.
  2. Brick-gray electrodes indicate that the mixture is ideal in composition and no additional adjustments are required.
  3. A white coating on the electrodes of the candle indicates that the mixture is depleted.

The signs outlined in points 1 and 3 indicate that adjusting the carburetor is extremely necessary for the Stihl 250 chainsaw.
NOTE! Adjusting the carburetor Stihl 250 with your own hands may be necessary for the owner if they have changed: fuel quality, height above sea level, or if an air depression has occurred at the site of operation of the chainsaw. Possibly, the air humidity, temperature, and atmospheric pressure have changed.
Exact settings will allow achieving maximum performance of the unit while reducing the necessary external conditions for its operation. Successful debugging of operating conditions prevent oil starvation and engine failure due to insufficient lubrication. After all, the lubricant enters the cylinder of the saw together with the lean fuel-air mixture.

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Preparing to adjust the carburetor.

Of paramount importance when adjusting all the characteristics of the fuel metering model, Stihl 250 has the uppermost adjusting screw located near the muffler. The factory setting, the parameters of which are depicted on the top plastic cover, stipulates that it should be unscrewed one turn from a full twist.
Throughout the process of operation, the carburetor adjustment of the Stihl 250 chainsaw is made by hand. Unscrewing the screw enriches the working mixture since the air-fuel mixture gets more gasoline, and turning the screw depletes the working mixture since the air-fuel mixture gets less gasoline.

Adjusting the carburetor will not give positive results if there is a leak of air from the engine through:

  • carburetor gasket;
  • rubber ring accelerator pump;
  • crankshaft oil seals.

Adjusting the carburetor Stihl 250 is carried out only after a careful examination, identifying the existing air suction. The next stage of preparatory commissioning is the full maintenance of all components and mechanisms.

It includes:

  • cleaning of deposits, slags, resins;
  • engine wash using solvent, acetone;
  • replacement of the spark plug;
  • cleaning, washing the air filter;
  • checking the tension of the cutting chain;
  • idle setting;
  • engine warming up to operating temperature.

Then you can proceed to complex configuration manipulations.

Adjusting the carburetor chainsaw Stihl 250.

Step-by-step adjustment of the Stihl MS 250 carburetor with a rev counter is performed in the following sequence:

  1. To stop the engine, fasten screws H and L to the stop, then turn them both out one turn.
  2. Engine start, warm up. At maximum revolutions of the screw N, achieve a maximum crankshaft frequency of 14,000 rpm, fixed by a tachometer or an engine speed counter. Hold the maximum engine speed for no more than 10 seconds.
  3. Bolt LA idle stop to achieve the beginning of the movement of the chain. After that, turn the LA bolt ΒΌ turn counterclockwise.
  4. Check the acceleration of the Stihl 250 chainsaw mechanism. The carburetor adjustment continues if the idle speed is unstable or the chainsaw accelerates insufficiently. Screw L must be turned slightly counterclockwise. Saw at the same time should quickly gain momentum, operate steadily at idle. Finalize the work of the screw LA. On the tachometer, the idle speed should correspond to a catalog value of 2800 rpm.
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Similarly, adjusting the carburetor chainsaw Stihl 211 with your own hands.
In his article, the author described in great detail all the details of the adjustment with the simple German production mechanism called the Stihl 250 saw. The carburetor adjustment is simple and accessible to every home artisan. By following the recommendations made by the author of the article, everyone can customize their Stihl 250 chainsaw and enjoy its flawless performance.

The ratio of the fuel mixture.

Engine oil for two-stroke engines STIHL 1:50:
1:50 = 1 part oil 50 parts gasoline
other branded motor oils for two-stroke engines for vehicle classification:
1:25 = 1 part oil 25 parts gasoline