STIHL ms 180 idle speed adjustment

STIHL MS 180 chain saw. technical specifications

The high performance of the STIHL model in the garden was achieved thanks to decent factory parameters.

Chainsaw specifications include:

  • Petrol engine power. 2 liters. с./1.5 kW;
  • factory cylinder volume. 31,8 cm3;
  • The allowable length of the bar to be used is 30-35 cm;
  • fuel consumption. 200 ml/h;
  • chain pitch. 3/8 ;
  • Weight incl. saw unit. 4 kg.

The German STIHL chain saw brand’s advantages include a low noise level of no more than 105dB when the engine is operating at maximum load.

stihl, idle, speed, adjustment

Adjustment required

Throughout the process of operation, it is periodically necessary to make additional adjustments and ensure the correct fuel-air mixture. How to determine when and what setting is necessary for the machine to work properly? There are characteristic signs when the mechanism, by the behavior of individual parts, itself prompts when adjustment is necessary.

First of all, the color of the spark plug electrodes should be checked before starting the engine each time.

By its change you can make a decision about the necessity of adjustment, adjustment of operating processes, improvement of the quality of the combustive mixture:

  • Black, soot-covered or carbonized electrodes indicate an over-enriched fuel-air mixture in the engine.
  • electrodes of brick gray color testify that the mixture is ideal in its composition and that no additional adjustments are required.
  • A white residue on the spark plug electrodes shows that the mixture is lean.

The indications given in points 1 and 3 show that a carburetor adjustment is essential for the STIHL 250 chain saw.

TAKE NOTE! The owner may need to adjust the carburetor STIHL 250 with his hands if the: fuel quality, altitude, or if the place of operation of the chain saw has become diluted air. Perhaps the humidity, temperature, and atmospheric pressure have changed.

Accurate adjustments are essential for getting the best performance out of your machine while reducing the external conditions necessary for its operation. Successfully adjusting the operating modes prevents oil starvation and engine damage due to insufficient lubrication. After all, the lubricant enters the saw‘s cylinder with a depleted fuel-air mixture.

How to repair a STIHL 180 with your own hands

All of the following applies to all chainsaw models, including chain saws, scythes and other machines. Adjusted, of course, for design considerations.

There is an opinion that it is better not to tamper with the chain saw yourself. For those who are used to working with a hammer and sledgehammer it may be. Otherwise any problem with its work can be fixed by any neat person who has not shaking hands. In general, it is a job available to anyone.

Of course it happens that the problem can’t be solved by yourself. And you need to go to the service center. But firstly, 90% of the problems are usually solved by simply flushing the jets or, in the worst case, replacing the diaphragms or adjusting the needle, and secondly, in the worst case, even if you are desperate, the carburetor removed from the saw can be easily replaced. The new original one is of course a bit pricey You can buy it in any store or from Russian dealers. In general, there is nothing to lose, let’s go to the carburetor!

Adjusting the carburetor of a chainsaw.

Ensures efficient operation of the tool at full power with economical fuel consumption. Adjustment should be done with clean fuel and air filter. For more carburetors, adjustment is made with three screws: maximum, minimum and idle speed.

H and L screws are used to adjust the gasoline/air mixture ratio determined by the carburetor throttle opening. when you unscrew the screws the mixture is enriched and the speed decreases respectively, when you tighten the screws the mixture is depleted. the speed increases.

The designation H refers to the maximum RPM screw that controls the main jets, L. to the minimum RPM screw that controls the idle speed nozzle. The S screw is used to precisely adjust the idle speed. Sometimes, to simplify adjustment, the number of available adjustment screws of the carburetor is reduced.

Setting the carburetor chain saw is divided into two stages. the basic (factory settings), carried out when the engine is off. and final, performed on a running warm engine. The exact values of the turning angles are to be found in the instruction manuals for your particular chain saw. Failure to follow the manufacturer’s instructions can result in engine damage.

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Basic carburetor adjustment.

The maximum H and minimum L revolutions adjustment screws should be turned slowly clockwise as far as they will go and then turn them back two revolutions

Checking and adjusting the idle speed.

Find the highest idle speed, to do this, slowly turn the screw L in different directions. After finding the position of the maximum engine rpm turn the L screw 1/4 turn counter-clockwise. If the chain still rotates at idle speed, the screw T or (S) should be turned clockwise until it stops.

Checking and adjusting the maximum rpm.

Changing the maximum rpm is done by turning the screw H. if the carburettor is turned clockwise, the engine speed increases and if it is unscrewed. decreases. Chainsaw engines have the highest rpm from 11500 rpm. up to 15000 rpm. A higher speed does not provide the ignition and becomes dangerous for the engine. If the RPM is too low, the ignition is out of sync with the rpm. if they are coming on, turn the screw H slightly anticlockwise.

If the engine is not tested for acceleration and maximum rpm the adjustment is not complete.

When the throttle trigger is pressed smoothly, the engine should confidently and quickly pick up speed from idle to maximum( from 2800 rpm.up to 11500-15000 rpm depending on the machine). If the revolutions are slow and lag behind, the screw L should be turned slowly anticlockwise, but not more than by 1/8 turn.

After adjusting the acceleration and maximum rpm, the saw should be checked again at idle speed. the engine should run steadily, the chain should not move. The adjustment of the chainsaw must be repeated if this condition is not met, but except for the basic adjustment step.

STIHL MS-180 chain saw carburetor

has only one tuning screw. the idle speed tuning screw. Do not dismantle the STIHL chain saw 180 yourself. it is better to leave this job to professionals. The full-load nozzle is stationary.е. unadjustable, and the full-load setting cannot be changed (the carburetor is set at the factory so that with all

The optimum fuel-air mix is delivered to the engine depending on operating conditions). No risk of damage to the cylinder and piston assembly as a result of improper carburetor adjustment. STIHL chain saws (including the STIHL 310) are listed in all specialty stores.

stihl, idle, speed, adjustment

On the Husqvarna-137 and Partner-351 chain saws the STIHL chain saw carburetor has three adjusting screws each, which requires careful carburetor adjustment The sprocket wheels are sealed in the bar housing and require no additional maintenance; there is absolutely no chance of dirt getting into the wheels.

Husqvarna and Partner tire sprockets need periodic lubrication through the holes (green arrows)

The lean mixture has an excess of air which is not good because it has its own disadvantages. Namely: insufficient burst energy (which means loss of power in the end), excessive cylinder heating due to insufficient lubrication and high rpm, which leads to scuffing, and there is not far to the engine jamming.

Most chain saws have three adjustment screws on the carburetor. Let’s talk about each in order:

  • T.Idle stroke screw. The idle speed screw controls the throttle valve position when the throttle grip is fully released. If the choke is not open enough, the engine will stall when the throttle trigger is released because the choke will restrict the fuel mixture. In case the choke is opened more than it should be, the chain will rotate, which is categorically forbidden by the chainsaw safety rules.
  • L-low speed adjustment screw. This screw controls the amount of fuel in the fuel mixture when the chainsaw is idling. If fuel quantity is too high, engine will choke under load and if fuel is insufficient, engine overheating, scuffing will result.
  • H-RPM adjustment screw. Controls the amount of fuel in the mixture when the chain saw is in operation. If the given adjustment is adjusted for a larger amount of fuel, the engine will run uncontrollably and smoke, and if it is adjusted for a smaller amount of fuel, you will get too high RPM and overheating.

Why the STIHL 180 overflows and has some typical problems

After we have considered the structure of the carburetor, it is not difficult to determine the reason why the fuel enters the combustion chamber in a larger volume. It is caused by wear of the gasket between the compensator cap and carburettor housing. You may ask how it can affect?

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The answer is simple: when the gasket is compressed it pushes the overlaying diaphragm down by a fraction of a millimeter. It, in turn, presses harder on the yoke of the needle valve, it will open more than it should and the fuel comes in too much (begins to overflow).

How the STIHL 180 works: design, principle of operation

The major components of the STIHL 180 chain saw carburetor include the following:

  • fuel pump (with internal diaphragm);
  • main (diaphragm) chamber;
  • diffuser;
  • Throttle and air valves;
  • needle valve;
  • fuel injectors;
  • nozzle with valve;
  • No-load speed adjustment screw.

How it works is as follows. The chainsaw crankcase is connected to the fuel pump in the carburetor by a special channel. the negative pressure in the crankcase is created by the alternating stroke of the piston. So the diaphragm in the fuel pump rises and the valve opens to deliver fuel to the carburetor.

Fuel then passes the filter element (screen) and through a special channel enters the main chamber. In this chamber, there is a control diaphragm, which regulates fuel supply by pushing on the rocker arm, which in turn lowers the needle valve.

For raising the control diaphragm, the vacuum created in the carburettor throttle body by turning the air valve and throttle valve. As soon as the engine is started, the mixture has to be lean. Lowering the choke, the vacuum in the diffuser is minimal, the diaphragm falls into place.

From the main chamber the fuel enters the diffuser by means of the return valve nozzle or through the idle speed nozzles (when the throttle is closed). There it mixes with the intake air and the ready mixture enters the engine cylinder. A check valve prevents air from the diffuser from entering the main chamber.

Saws crookedly

Let’s find out why a chainsaw cuts awkwardly. It shows up when sawing under load, when the guide bar moves to the side little by little. This is especially noticeable when sawing a wide barrel by double-cutting, first from the top, then from the bottom. The result is an uneven cut surface, which in some cases is unacceptable. Example. facing bars.

  • Uneven sharpening of saw teeth. This is the most common cause of why the unit saws askew. The teeth should be ground to the same distance to avoid problems when sawing. The optimal solution is to purchase a sharpening machine that is adjusted to the most worn tooth of the saw mechanism. Or go to a workshop with such equipment. The result. all the teeth are the same size.
  • The chain or guide bar you are using does not match the parameters. When buying these elements, the width of the groove must be taken into account. This is important not only for proper operation of the equipment but also for safety when sawing.
  • The saw headset of the device is badly worn. If the device saws poorly, there may be increased wear on the headset. Visual inspection will indicate the problem. If the right or left side of the bar is more worn, it must be replaced with a new one. If there is a lot of wear, it makes sense to have the lubrication system checked completely. This is often the cause of excessive wear on one side of the chain.

In case of complicated repair, it is better to take the equipment to a specialized workshop.

Not starting the saw: causes and solutions

There is either air suction or something is blocked.

To fix STIHL MS 180 chain saw faults disassemble, flush and blow out the carburettor, change fuel filter in the tank, check fuel hoses for cracks (air might be sucking in).The regulating screw on the carburetor only one. idle speed (sometimes, twist it, and the chainsaw works again).The connection between the carburetor and the cylinder, in terms of air suction, is reliable. there is a plastic ring (no gaskets required).

chain saw is running at high rpm right after starting, but when you accelerate it “crushes” instead of starting to accelerate and even stops. Or it fails to start, it has no power and shuts down (this fault also applies to other more expensive chain saws with a booster pump in the carburetor).

Cause of chainsaw malfunction: The rubber sleeve on the booster pump piston in the carburetor (fuel booster) is worn. It results in air suction by the booster pump and the main nozzle supplies the depleted fuel-air mix to the nozzle (there is not enough gasoline in the mix) and the chainsaw first operates at a higher rpm and then “crushes” and shuts down. It happens after 2-3 years of operation and usually in the hot summer months.

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Remove the carburetor from a chainsaw. Remove the gasoline pump cover with the diaphragm by removing the screw in the center of the cover. Next, turn the carburetor towards yourself with the throttle, on the side where there are two holes, in one you can see a pin, here under it is the booster pump. Remove the retaining ring on the outside of the pin and disconnect the wire spring from the air damper.

Unscrew the screw in the center of the throttle, remember how the throttle is facing (to put it in the same way later) and remove the throttle. Use your finger to put a pin in the hole (the gas pedal is spring loaded and if you remove the throttle body and leave the hole open the gas pedal will pop out) then turn the throttle body and remove it.


Shake the booster (piston) and spring out of the hole. There is a rubber sleeve (ring) on the piston that is the cause of the chainsaw malfunction. It is necessary to replace the piston with a rubber cuff and spring (they are sold as a repair kit). Or you can take out the worn piston and the spring, and plug the hole by pushing in a rubber plug (the chainsaw will be without booster pump, t.е. It won’t accelerate in three seconds., but in 4 seconds., but will run well as there will be no air suck by the carburetor).

Reassembly after troubleshooting the chainsaw (after troubleshooting the chainsaw carburetor) is done in the reverse order of disassembly. When assembling the throttle, before tightening the screw, the throttle itself must be properly aligned so that it does not jam, and the threads of the screw securing the throttle to the axle should be degreased and smeared with a special thread sealant (available in small tubes, red, liquid) or flatten with pliers, because if this bolt twisted during operation, it goes straight into the cylinder ) and repair or replacement of the piston is not avoided). Here we look at troubleshooting this chainsaw malfunction.

, it is worth noting the fact that the 180 saw from this manufacturer is one of the best in its “creations”, but also has its drawbacks. Actually, what we are talking about now.

Short video guide on how to change the membranes in the carburetor of chain saw.

The chainsaw does not start, floods the plugs, what to do. Group in the contact:.

When the spark plug on your chainsaw fills up, you need to do a thorough check of the tool immediately.

  • Checking the plug. Part of the regular maintenance of a STIHL chainsaw is to take the plug out and inspect it (we recommend every 10 to 15 hours of use.) If the engine is running normally, the outer electrode will probably be covered with light brown deposits. The operator must check the gap between the electrodes with a special tool. If the engine is running normally, the problem is evident in the condition of the plug. Thick black deposits indicate that the mixture of fuel and air is not balanced. In other words, there is not enough air in the mixture. On the other hand, wide gaps or corroded electrodes are indicators of a lean mixture. Oil on the plug indicates a leak.
  • Clean or replace? If the plug is covered with light brown deposits and the gap is correct, the operator does not need to do anything to the plug. It’s enough to put it back in place and the chainsaw should continue to operate normally. If it is covered with black deposits or oil, it is necessary to remove this layer with sandpaper. If necessary, adjust the gap with pliers. One condition that indicates the need for replacement is electrode wear. If the engine stalls, you need to check it with a spark plug tester and have it replaced if the spark is not strong or appears intermittently.

Short video tutorial on how to change the diaphragms in a chainsaw carburetor.

First of all, it is worth noting the fact that the chainsaw 180 of this manufacturer is one of its best “creations”, but it also has its drawbacks. Actually, which we are going to talk about.