Stihl 250 chainsaw does not start

Stihl MS 250. balanced chainsaw for agriculture

Stihl manufactures reliable chainsaws that are used in all areas of activity. Household, professional models, models for agriculture. One of the saws for agriculture will be discussed in this review. Saw Stihl MS 250.


The Stihl 250 chainsaw is supplied to the Russian market with two tires of different lengths as standard: 4 and 16 inches. Depending on the task, you can choose any, and with luxury versions, such as Stihl MS 250

When choosing a chainsaw, do not get too hung up on the length of the tire, if necessary, the tire and chain can be replaced with a longer one or vice versa after purchase.

The basic technical characteristics of the standard and improved model 250 saws are the same. Power 3.1 liters. s., which is translated into kW 2.3. This is 0.8 more than the household model Stihl 180. The working volume is 45.4 cubes. Turnover 11-13 thousand. Chain has 0.325 ” pitch and 1.3 link width.

The chainsaw weighs 4.6 kilograms. Volumes of oil and fuel tanks 0.2 and 0.47 liters, respectively.

Of course, according to the characteristics, it is difficult to determine how the chainsaw will behave in business, for this you need to try it in work and compare with something.

stihl, chainsaw, does, start

I have been using the Stihl 250 chainsaw for over two years. I work almost daily, but not all day, but 3-4 hours, including rest breaks. I’m happy with the saw. There are no problems with her at all. I poured gasoline and oil and went to work. For the entire period of operation there was only one malfunction, the cord on the starter was torn. I fixed it myself, the system is very simple there, everything is done within half an hour.

I use only branded oil and consumables, I do not pour working off, so the tire is still native, and it has been preserved well, although the saw has already cut a lot.

Chain brake

One of the safety mechanisms when working with a chainsaw is the manual inertial chain brake. If, for some reason, the tire of the chainsaw makes a sharp rebound, the brake will turn on and the chain will instantly stop spinning, thereby reducing the risk of serious injury. For the chain brake to function properly, the operator must comply with several conditions:

  • Hold hands as instructed, i.e. left hand on the front handle, right hand on the back.
  • Clean the mechanism in a timely manner, since it is located in the side cover, where a huge amount of sawdust falls.

Stihl MS 250 C – BE

For even greater customer comfort, Stihl produces models equipped with an improved modification. Their letter designation can be deciphered knowing what each specific letter means.

(E). a starter with a special spring is installed on the saw, which reduces the load when starting the Stihl 250 chainsaw, making the start smooth and comfortable. The system is called ElastoStart.

(B). a chain tensioning system is installed on the saw without the use of additional tools. Thanks to which, the operator does not need to carry tools with him. And this is quite convenient.

(C). means that the saw with modified gasoline and oil tank caps. It is not difficult to open such lids, but they have no chance of unscrewing them on their own, as is the case with ordinary lids.

Why the Stihl 250 chainsaw won’t start

Sometimes there are situations where the saw may not start. As a rule, more than 50% of the saws that did not start and were delivered to the service center did not start due to a violation of the cold start algorithm.

Combined control

Another system that adds convenience and ease of use to the Stihl 250 is the combined control lever. Thanks to which, the ignition is turned on and off with the thumb of the left hand. The suction mode is also activated in the same way. The switch never needs to be looked for, it is always at hand, which is especially convenient in the event of an emergency.

Chainsaw “Stihl-250″: problems with the hot plant

I have a Stihl-250, old man, a problem has arisen: it starts up on a cold one without problems, you start it on a hot horseradish until you burn the unburned mixture through the muffler. I put a new candle, washed and cleaned the filter, washed the carburetor too. Anyway, the problem remains, please tell me how to solve it?

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Checking the muffler

Most likely, the reason lies in the muffler, which is clogged with combustion products (deposits) or just debris. It is enough to clean it, and the normal operation of the chainsaw will be restored. To do this, it is best to dismantle this part and wash it using ordinary detergents (aggressive ones can be used). Then rinse the muffler thoroughly with clean water and dry with a hairdryer.

Muffler cleaning is usually beneficial.

Be careful when cleaning: carbon deposits contain carcinogens that, if ingested, can be harmful to health if they enter the lungs. The reason for the appearance of soot is the wrong ratio of gasoline and oil poured into the tank. Most users prefer to do this by eye. But keeping the exact proportions is not difficult: just use a disposable syringe without a needle of the appropriate volume.

Other reasons

Here, first of all, we mean the wear of the cylinder, piston, rings, and also the crankshaft bearings. The failure of these elements ultimately leads to a drop in compression (pressure) in the cylinder. You can check the state of the CPG along the way when you remove the muffler. After dismantling this part, you will see a window through which part of the cylinder is visible. If there are any scuffs or scratches on it, then it will have to be changed.

Next, you need to check the compression. If there is no special device, remove the plug, plug the hole with your finger and pull the starter cord. With good pressure, the finger will be sucked inward. If there is a compression gauge, but it must be inserted into the spark plug hole. Also crank the crankshaft with the starter and look at the readings on the gauge. The normal parameter is 8-9 kgf / sq. cm (which corresponds to 0.8-0.9 MPa). The reason for the low compression may not necessarily be in a worn cylinder or piston: sometimes it is enough to replace coked rings.

How to set the ignition

It is necessary to set the ignition on the chainsaw. The ignition is adjusted as follows:

  • turn out the candle and evaluate its appearance;
  • specify the distance between the magnets and the coil (up to 0.2 mm);
  • check the spark.

Cold Starting a Stihl MS250 After Not Using It For Years

Repair of the cylinder-piston group (CPG)

If the engine of the chainsaw does not start or cannot develop normal power, it is likely that sufficient pressure does not build up in the engine cylinder for combustion of the fuel mixture. The reason for this may be the wear of the elements of the cylinder-piston group. the piston, rings, bearings, etc. In order to assess the condition of this unit, it should be visually inspected, having previously removed the muffler.

For a more complete diagnosis, a compressor is placed in the spark plug hole of the two-stroke engine of the chainsaw. It measures the compression in the engine. Based on the results of the check, one can judge the state of the CPG, however, accurate facts can only be obtained with a complete disassembly of the unit.

If the piston is chipped or scratched, it will obviously need to be replaced. The same applies to deformed or broken piston rings. for normal engine operation, they must be completely intact and free of carbon deposits.

DIY chainsaw repair: fuel supply system

If the fuel mixture does not flow into the cylinder, but the spark plug is working properly, this may mean that:

  • Clogged fuel filter.

To clean this unit, remove the fuel hose and check the jet. If it is weak, the filter must be removed through the filler hole of the fuel tank and cleaned or replaced if completely worn out.

As a preventive measure, it is recommended to replace the fuel filter at least once every 3 months.

This is nothing more than a hole in the fuel tank cap, which is cleaned with an awl.

  • Fuel mixture not supplied or not supplied in sufficient quantity.

There may be several reasons for this:

  • the air filter is clogged (in this case, it must be removed, rinsed with water, dried and replaced);
  • the carburetor settings are out of order (which means this unit needs to be re-adjusted);
  • the integrity of the carburetor membrane is broken (must be replaced);
  • the channels of the carburetor are clogged (it must be disassembled and all parts and assemblies must be cleaned).

Doesn’t develop momentum

If the saw does not maintain idle speed, then the following may have happened:

  • clogged filter;
  • violation of the ignition system;
  • the carburetor has deteriorated;
  • parts of the motor are deformed.

For self-repair, you need to follow these steps:

  • Flush or replace the fuel hose.
  • Clean filter.
  • Check the quality of gasoline and oil.
  • Check the operation of the carburetor and spark plugs.
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When the Stihl chainsaws are repaired, they will work correctly.

If the saw is not gaining momentum, then this could lead to:

  • faulty engine;
  • cylinder wear;
  • failure of piston rings;
  • breakage of the spark plug;
  • coil malfunction;
  • unbalance of carburetor screws.

If, after testing, no defects are found, then check the carburetor.

Replacing the starter cord

Remove the side cover. Inspect the inside of the protective casing. If there is no damage, check the launch unit. Unscrew the starter bolt and remove the spring. Diagnose a pulley with a cord. If the rope is intact, then each part of the launch mechanism is checked:

The starter cord is made of synthetic material and will gradually wear out. If it is damaged, cracked or torn, then it must be replaced.

The chainsaw is a worthy replacement for hand saws and axes. Today, this tool is available in almost every household. it is indispensable for setting up a personal plot, construction and repair work. Intensive use and improper care of the tool can lead to premature failure. However, the owner of the chainsaw does not have to go to the workshop right away. many of the faults that can happen to her during operation are quite realistic to eliminate on their own.

Carburetor repair and adjustment

The carburetor is adjusted on a warm engine. If the engine fails to tune, the carburetor stuck may cause excess gasoline in the mixture. To remove the part, it is necessary to unscrew the fastening nuts, disconnect the ignition and the rod from the engine control lever. Then the lever is removed. Then you can remove the filter and carburetor.

The muffler is secured with two nuts. You need to untwist them and pull the muffler towards you. Then the screws of the coil are unscrewed and dismantled. On the Stihl saw, the carburetor has 1 idle adjustment screw. If the idle speed is violated, then the carburetor needs repair. This is a complex process and difficult to do on your own. Contact a repair shop.

How to remove and replace an asterisk

Chainsaw sprocket replacement is needed when:

  • jams the movement of the chain;
  • the drive sprocket is worn out.

To replace, you need to remove the chain saw sprocket. The sprocket teeth must not deviate from the required dimensions, otherwise the saw operation will be accompanied by vibration, which will lead to damage to the crankshaft and bearings. The lifespan of the sprocket is 2 times that of the chain. Use 2-3 chains until the cutting surface is abraded. After that, change the asterisk. It is located behind the clutch. Remove the clutch cover.

Remove the bar, chain, and clutch. But first you need to fix the crankshaft. Then the stripper is placed in the hole of the sleeve and turned clockwise. Remove the clutch. There is an asterisk behind it. Now it is being dismantled. If it is defective, it is replaced.

Stihl Chainsaw running poorly? Here’s a quick fix.

Calibration algorithm and safety precautions when troubleshooting chainsaw carburetor

Carburetor adjustment is carried out in two stages:

  • Basic (carried out with the engine off).
  • Finishing (carried out with a running, pre-warmed engine).

For basic adjustment, screw in screws H and L as far as the stop and back out 1.5 turns. Final adjustment requires the engine to warm up for 5-10 minutes at low revs.

The final calibration is performed by unscrewing the idle screw until the minimum engine speed is reached (in this case, its operation must be stable, and the chain must be stationary). If the engine stops at idle speed, the screw must be returned back, and if the saw chain is still in motion, continue turning counterclockwise.

Calibration check is performed by test:

  • Acceleration (with a smooth press on the accelerator, the engine should quickly pick up speed to the maximum indicator).
  • Maximum speed (if there is an ignition interruption, screw H should be slightly loosened).
  • Idle work (the chain should not move, and the engine should pick up speed as quickly as possible).

If the owner of the chainsaw is not familiar with the carburetor device and does not have the necessary tool to calibrate it, contact a specialist. The carburetor is a very complex unit, so any wrong action can lead to irreversible consequences, for example, complete engine failure.

Stihl chainsaw stalls: reasons

If the tool turns off immediately after starting, it means that a breakdown of some device or part has occurred. To determine the cause, the mechanism is tested independently or in service workshops. Sometimes the reason that the mechanism does not start well is due to improper saw maintenance:

  • insufficient amount of gasoline;
  • poorly prepared fuel mixture;
  • poor quality lubrication;
  • muffler clogged with combustion products;
  • unregulated carburetor;
  • obstruction of the air filter;
  • malfunction of the piston or cylinder.
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Broken crankshaft bearings

In case of bearing defects, a slight backlash is felt. To detect it, the flywheel of the Stihl MS 180 saw is swinging from one side to the other. The movement indicates that the flywheel is being pushed towards the electrodes by its own magnets, resulting in the absence of a spark. To remove the mechanism, dismantle the cutting element, remove the filter and clutch cover. For the crankshaft stopper, remove the manual starter cover and tighten the two bolts.

The clutch is unscrewed with a wrench clockwise. They remove the drum with an asterisk, change the old clutch and twist it all the way. The crankshaft is locked so as not to break the starter. The mechanism is assembled in the reverse order. To tighten, the brake handle is tilted forward, the tool is turned on, then released from the brake.

Bearings with defects are less often detected (the diameter of the holes in the cage is increased). For determination, disassemble and measure with a micrometer. Broken bearings are indicated by regular knocking. In this case, urgent repair is required, since if the integrity of the crankshaft is violated, the piston group and the cylinder will fail.

Idle speed adjustment

Before commissioning, the tool is maintained. In order for the idle speed adjustment to be effective, prevention is done:

  • cleaning the carburetor;
  • flushing the engine;
  • cleaning the air filter;
  • warming up the engine.

To adjust the operation of the mechanism at idle speed, an appropriate adjusting screw is used. Its rotation depends on the required setting:

  • With standard adjustment, the screw is turned against the clock hand to the point where it will turn tightly. After that, make 2 circles in the direction of the arrow.
  • If the saw is running at low speed, turn the screw clockwise until the chain starts moving. Then make half a circle in the opposite direction.
  • At high frequency, the regulator is turned against the clock hand until the circuit stops. After that, the rotation is continued for another half turn in the same direction.

It will not work to adjust idle operation if there is air suction into the engine through a gasket, acceleration pump, oil seals, or for another reason.

Doesn’t slow down

The tool quickly reaches its maximum number of revolutions and the power does not decrease. This situation is explained by the fact that:

  • the throttle valve does not work due to a weakening of the spring or traction element;
  • the turning on toggle switch periodically fails;
  • no corkscrew on the throttle shaft;
  • clogged carburetor;
  • the fuel hose and the petrol filter are malfunctioning.

Why the Stihl chainsaw won’t start

For a preliminary diagnosis of the reasons, check the operation of the gas pump, the appearance of the plug, the flow of fuel, the functionality of the carburetor and the condition of the filter. Pay attention to the performance of cylinders, pistons, muffler, crankshaft bearings. After preventive measures, they try to start the chainsaw. Insufficient lubrication of rubbing parts also becomes a factor in poor performance.

In this article, we will consider the main problems that may arise when starting the Stihl chainsaw (the spark is gone, the tool stalls or does not pick up speed), as well as ways to eliminate them.

Not gaining momentum

Many systems of the mechanism are involved in the start-up, therefore, the loss of speed of the Stihl chainsaw after idling can be a consequence of various factors. Confident idle operation and interruptions in the motor under load can occur for the following reasons:

  • development of the engine resource;
  • wear, deformation and corrosion of the piston group;
  • malfunction of the ignition coil or spark plug;
  • unbalance of carburetor screws.

If the tool does not develop speed, then the conductivity of the hole in the fuel tank cap is broken. The emergence of a vacuum does not provide the required amount of fuel, therefore the engine does not gain the required power. Turnover decreases when carbon monoxide accumulates in the muffler, it is difficult to remove gases from combustion.

stihl, chainsaw, does, start

At full speed

Sometimes the engine will stall after normal operation. To establish the cause, pay attention to the accompanying circumstances:

  • The motor stalls in the middle of operation for no apparent reason. The starter is stationary and does not turn. It means that the tool is jammed and requires urgent repair.
  • During normal operation, the power is reduced in a short time and the engine stops, the cylinders are overheated. The situation indicates the occurrence of air suction under the rubber pipe between the carburetor cylinder, possibly due to a rupture. Air depletes fuel, nozzle replacement required.