Adjusting The Chainsaw “Stihl Ms 250” Carburetor.

The necessity of the operation “Adjusting the carburetor of the chainsaw” is determined by the colour of the spark plug electrodes: if black. means over-enrichment, if brick-gray. this means the norm, if white deposit on the electrodes of the candle. means lean mixture.
The leading role in adjusting the carburetor chainsaw Stihl plays the upper screw (closest to the muffler). According to the factory parameters (indicated on the chainsaw cover) it should be unscrewed for 1 turn, and then it is necessary to correct it. if it is unscrewed, the working mixture is enriched (more gasoline gets into the air-fuel mix), if this screw is screwed in, the working mixture is depleted (less gas gets into the air-fuel mixture).

Adjusting the carburetor chainsaw STIHL MS 250 (with rev counter):

Before adjusting the carburetor of the Stihl chainsaw, it is necessary to perform maintenance of the chainsaw (cleaning the carburetor of the chainsaw, wash the chainsaw engine, replace the spark plug, clean the air filter, check the chain tension, adjust the idling speed, warm up the engine).

  1. Turn the screws “H” and “L” (on the muffled chainsaw) to the stop, and then both turn them out one turn.
  2. Start a chainsaw and warm up. Drive full throttle and screw “H” to ensure that the maximum engine speed is 14000 rpm. by tachometer (by engine speed counter). The maximum speed for adjustment to keep no more than 10 seconds!
  3. Bolt “LA” idle stop to make the chain start to move, and then turn this bolt ¼ turn counterclockwise.
  4. If, after this adjustment of the carburetor of the chainsaw, the idle speed is not stable and the chainsaw accelerates poorly, then you need to turn the screw “L” slightly counterclockwise until the chainsaw quickly gains momentum and work well at idle. Then adjust the bolt “LA” (idle speed on the tachometer should be 2800 rev/min). Attach.

Note: Adjusting the carburetor of the chainsaw will not work if there is a leak of air into the engine from the side (through the gasket under the carburetor, through the accelerator pump of the carburetor, through the glands of the crankshaft of the chainsaw or somewhere else).


Adjusting the carburetor chainsaw Stihl may be needed when changing the quality of fuel, height above sea level, which is operated chainsaw Stihl (air vacuum), as well as changing the atmospheric pressure, temperature and humidity. Setting the carburetor chainsaw allows you to achieve excellent performance chainsaws with a deterioration of external conditions. Also, adjusting the carburetor of the chainsaw helps prevent oil starvation and engine damage due to insufficient lubrication entering the cylinder with a lean fuel mixture.

Tip: To check the tightness of the engine is very good to use a special device, i.e. special pump with pressure gauge. First, you need to remove the carburetor on the chainsaw and install an airtight lamellar plug with a flange on the inlet window of the cylinder to connect the hose from the pump. Spark plug for tightness can also be put on the sealant. It is also necessary to remove the silencer and install an airtight plate with a rubber gasket on the exhaust port of the cylinder. Then you need to put the piston in the upper dead center and connect the hose from the pump to the flange. Further, it is necessary to pump air into the engine to 0.9 atm. and look at the gauge arrow. if it stands still, then the piston of the engine is tight. Then we release the air, switch the device (pump) and start pumping out air from the cylinder, creating a vacuum in the engine with a pressure gauge reading of.0.5 atm. We look at the gauge needle. if it stands still, it means there is no air leaks through the glands or other seals in the engine (which impairs the operation of the chainsaw and does not allow correct adjustment of the carburetor of the chainsaw). Thus we check the engine for air leaks and compression.

Adjusting the carburetor chainsaw Stihl 180.

  1. Standard idle speed adjustment (abbreviated HH): turn the screw counterclockwise until it is tight, and then we make two turns per clockwise, that’s all.
  2. If the speed of xx is too low. you must turn the screw clockwise until the chain begins to move, and then turn the screw 0.5 turns counterclockwise.
  3. If the speed is too high xx you must turn the screw counterclockwise until the chain stops rotating, and then turn the screw another 0.5 turns counterclockwise.

That is all, adjustment of the carburetor chainsaw Stihl 180 is over.


The carburetor of the chainsaw is a part of the fuel system of the chainsaw designed for mist-mixing gasoline with air and dispensing the supply of this fuel mixture to the engine cylinder.
Note: The chainsaw carburetor mixes gasoline with air in the ratio of 1:14, i.e. 1 part of gas and oil is mixed with 14 pieces of air, and the adjustment of the carburetor of the chainsaw provides the correct ratio of these components of the fuel mixture.