Dismantling the Stihl Ms 660 Chainsaw

Stihl does not use off-the-shelf components from outside manufacturers to assemble their chainsaws. Therefore, the original Stihl MS 660 chainsaws have carburetors manufactured by this company. On Chinese chainsaws can be carburetors manufactured by Walbro, Rezer, Kimoto, Cingcong, as well as other unknown manufacturers.

Which carburetor is installed on a Stihl MS 660 chainsaw

The Stihl MS 660 chainsaw carburetor is of the membrane type, which allows it to work even in an inverted position. The company has more than half a century of production of chainsaws, so each node is quite perfect.

Dismantling the Stihl Ms 660 Chainsaw

Non-original products from other manufacturers most often have an identical design.

The Stihl MS 660 chainsaw is one of the most powerful in the world (7.1 hp), a professional class.

Therefore, the carburetor on it is characterized by increased throughput, sufficient for such an engine size, and reliability.

The device and principle of operation of the carburetor chainsaw Stihl MS 660

The carburetor of this model consists of almost 50 parts, including fasteners.

The main components of the carburetor chainsaw Stihl MS 660:

  • Housing made of light alloys of non-ferrous metals, with supply channels for the fuel-air mixture, storage chamber.
  • Diffuser and chamber in the housing for spraying fuel.
  • Jets with calibrated openings for metered fuel supply.
  • Air and throttle valves.
  • Needle valve for opening and closing the gas supply channel from the tank.
  • Elastic membrane that defines the position of the needle valve.
  • Manual fuel pump for starting a cold engine (primer, or suction).

At the first start of the cold engine of the chainsaw, gasoline is manually pumped up with the primer button. The first jerks of the starter are made with the choke closed. After setting and during engine operation, the air damper opens.

During operation of the internal combustion engine, a vacuum forms in the combustion chamber, and the mixture is sucked in automatically.

At idle, the intake of the mixture is limited by a closed throttle with an opening for the passage of a small amount of fuel.

The throttle position is adjusted when the chainsaw is operated by a gas handle. When the handle is pressed, it opens, the fuel supply to the internal combustion engine increases, and vice versa.

On a note! A mixture of low gasoline and lots of air is called lean. Conversely, a mixture with more gas and less air is called enriched.

For normal operation of the internal combustion engine, the mixture should be optimal in proportion to fuel and air, which is achieved by adjusting the carburetor of the Stihl MS 660 chainsaw.

Do-it-yourself carburetor adjustment for the Stihl MS 660 chainsaw

All carburetors on Stihl MS 660 chainsaws are factory-set on equipped stands. This provides the best parameters of the internal combustion engine in all modes. Settings get lost extremely rarely. Before adjusting, make sure that it is necessary. Deterioration of the engine can be caused by other reasons:

  • Air filter clogged.
  • Clogged with spark plugs and silencer outlet pipes.

If there is no problem with them, or they are resolved, and the internal combustion engine is not working properly, start adjusting.

The Stihl MS 660 chainsaw carburetor has three adjusting screws:

  • LA for idle adjustment.
  • H for adjusting the fuel supply at high speeds (main screw).
  • L to adjust the proportions of fuel and air (mixture quality screw).

Screws L and H are located nearby, LA at a distance from them. All of them are marked on the case.

What you need to adjust

To access the adjustment, just remove the upper housing cover and air filter. Therefore, only a screwdriver for the slots of the adjustment screws is required from the tool.

For professional carburetor adjustment, an electronic tachometer is required. It accurately indicates the idle and maximum speed. The idle speed of the Stihl MS 660 chainsaw is 2,500 per minute, the maximum. 13,000 per minute.

Without a tachometer, the quality of carburetor adjustment is determined by ear and by the actual operation of the internal combustion engine chainsaw.

Standard or basic setting

Screws H and L are tightened clockwise to the end, counting the number of revolutions made. Their number is recorded or remembered. If as a result of an unsuccessful carburetor adjustment it is not possible to start the engine, this data will allow you to return to the original factory settings.

  • Screws H and L are unscrewed counterclockwise, each 1 turn.
  • The engine is started and checked in operation by ear or by tachometer.
  • If the revolutions fail (suffocates) when you press the throttle, screw H is unscrewed another 1/4 turn.
  • If the engine is idling when the throttle is pressed, turn the screw L. 1/4 turn.
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Each Stihl MS 660 chainsaw that has worked for some time has its own characteristics, including the compression ratio in the cylinder. Therefore, the setting is individual. By turning 1/4. 1/3 of the H and L screws in one direction or another, they achieve optimal operation of the chainsaw engine at medium and maximum speeds.

Current setting

Experienced operators in the process may notice that the internal combustion engine of a chainsaw began to work worse. Sometimes it is enough to turn the H and L screws alternately in one direction or another by a small step of 1/5. 1/6 turn and immediately check the result of adjusting the carburetor in real work. This is one of the easiest ways to achieve good customization.

The video material contains information on how to adjust the carburetor of the chainsaw and check the result of the setting.

Idle speed adjustment

Held with an LA screw.

Adjustment is required if the engine stalls at idle. low speed, or the chain scrolls. high speed.

Turns are reduced by tightening the LA screw counterclockwise until the chain stops, then turn back 1 / 5-1 / 4 turns.

Adjustment with the LA screw is almost always required after adjusting the L screw, which also changes the parameters of the engine’s idle operation.

Screws LA and L regulate single turns basically differently. L changes the quality and quantity of fuel supply through calibrated holes. LA is called “retaining” because it affects the throttle position at idle.

Features and differences of carburetor adjustment on a Chinese chainsaw

Carburetors on Chinese chainsaws are mostly copied from the original Stihl design. Therefore, the adjustment algorithm on the original and Chinese versions is almost identical.

Non-original products are worse because they use low-quality alloys, short-lived plastic parts (membranes and gaskets), the sizes of calibrated holes are not precisely maintained, etc.

For educational purposes, we recommend watching an interesting video about the Chinese Stihl МС 660 chainsaw. The chainsaw is completely disassembled, the condition of components, including the carburetor, is assessed. Also, the author of the video disassembles the carburetor and on an example shows how to clean it from dirt.

What is the difference between the Stihl MS 660 carburetor and the Stihl MS 650

Stihl MS 660 and MS 650 belong to the same class of powerful professional chainsaws, close in technical characteristics and design. The Stihl MS 660 has a combustion chamber volume of 91.6 cc with a power of 7.1 hp.

Stihl MS 650. 84.9 cc and 6.7 hp They are almost identical in appearance with carburetors, which are regulated according to one algorithm.

The design differences are that on the carburetors of the Stihl MS 650 chainsaw, calibrated holes in the nozzles and channels of a smaller diameter are used.

Video: Dismantling the Stihl Ms 660 Chainsaw


The original German Stihl MS 660 chainsaw carburetor does not apply to consumable units that must be replaced after a certain service life. The service life for which it is capable may exceed the life of the chainsaw as a whole.

Adjusting the carburetor of the chainsaw ensures efficient operation of the tool at full power with economical fuel consumption. Adjustment must be carried out with a clean fuel and air filter. For a larger number of carburetors, the adjustment is carried out by 3 screws: for maximum and low revs and adjustments idle move.

The H and L screws adjust the gas / air mixture ratio determined by the opening of the throttle carburetor. On a Stihl ms chainsaw, carburetor adjustment is a guide to a Stihl ms 660 chainsaw. When the screws are loosened, the mixture enriches and the revolutions decrease accordingly, when twisted, the mixture becomes leaner. the revolutions increase.

The designation H refers to the maximum speed screw that controls the main jet, L to the minimum speed screw that controls the idle jet. Screw S provides precise speed control idle move. The article describes in detail the adjustment of the carburetor of the chainsaw with three adjusting screws, as well as the adjustment of the carburetor of the Stihl 180 chainsaw with one screw. Sometimes, to simplify the adjustment, the number of carburetor adjusting screws available is reduced.

Setting the carburetor of the chainsaw is divided into two stages. the basic (factory settings), carried out with the engine turned off, and the final, made with the engine running warm. The exact angle of rotation should be taken from the operating instructions for the particular chainsaw. Failure to follow the manufacturer’s instructions could result in engine damage.

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How to adjust a chainsaw carburetor. Maintenance chainsaws. Dismantling the carburetor chainsaw Chinese Stihl 660 does not adjust the carburetor on. Part 11

In this video we will answer the question of how to configure or adjust carburetor chainsaw do it yourself

Chinese Stihl IGNITION and carburetor adjustment.

In this video I will show how to set the ignition on chainsaw and how to set up carburetor for benz.

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Basic carb adjustment.

The adjusting screws for the maximum H and minimum L revolutions are slowly turned clockwise until they stop, after which they are turned back 2 turns, other settings are also possible

Check and adjustment of idling.

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We find the highest idle speed, for this, slowly turn the screw L in different directions. After finding the position of the highest engine speed, turn screw L 1/4 turn counterclockwise. The article describes in detail the adjustment of the carburetor of the chainsaw with three adjusting screws, as well as the adjustment of the carburetor of the Stihl 180 chainsaw. If the chain rotates at idle, screw T or (S) should be turned just clockwise until it stops.

Check and adjustment maximum speed.

Changing the maximum number of revolutions is carried out by screw H. When it is screwed in (clockwise rotation), the speed increases, when turned out, it decreases. Chainsaw engines have the highest rotation speed of 11,500 rpm. up to 15000 rpm Ignition does not provide a higher speed, in addition, it becomes dangerous for the engine. The maximum speed can be determined by interruptions in the ignition. Do-it-yourself carburetor adjustment for the Stihl 250 chainsaw. For the small, compact Stihl 250 chainsaw mechanism, proper carburetor tuning is key. If they come, screw H is slightly turned counterclockwise.

If the engine is not tested for acceleration and maximum speed, then the adjustment of the chainsaw cannot be considered complete.

With a smooth pull of the gas trigger, the engine must confidently and quickly gain speed from idle to maximum (from 2800 rpm to 11500-15000 rpm, depending on the unit). Carburetor adjustment chainsaw Stihl ms 660 video. If rpm is slow, delayed, screw L must be slowly turned out against clockwise, but not more than 1/8 turn.

After adjusting the acceleration and maximum revolutions, you should again check the operation of the saw at idle. the engine should work stably, the chain should not move. Chainsaw setting should be repeated if this condition is not met but with the exception of the basic adjustment step.

Owning a chainsaw in many ways makes life easier even for an amateur, and in some professions this tool is practically indispensable. However, like any relatively complex device, a chainsaw requires periodic maintenance. Due to untimely or poor quality maintenance, as well as the result of both planned and excessive loads, various kinds of malfunctions can occur. For professionals, interruptions or unstable operation of the saw reduce the efficiency of work or can cause a spoiled working day. One of the most common malfunctions is the incorrect setting of the carburetor of the chainsaw, which fails due to unsuccessful attempts to adjust or shift the adjusting screws for other reasons.

Symptoms of malfunctions and breakdowns that require carburetor tuning.

The following symptoms and malfunctions indicate the need for carburetor adjustment:

  • the engine starts with a strain and stalls almost instantly;
  • gas consumption is excessively large, the exhaust is too thick, the combustible mixture in the cylinder does not completely burn;
  • the factory settings of the carburetor of the chainsaw are knocked down (due to vibrations or unsuccessful attempts at regulation);
  • malfunctions of the air cleaning system, leading to the ingress of particles of debris into the mechanism distributing the fuel mixture;
  • significant wear of the piston group. the carburetor setting in this case acts as a temporary measure.

It is clear that if dirt enters the fuel system with one setting, the problem cannot be solved. it needs to be flushed. In the case of worn piston overhaul is required. However, in all these cases, carburetor tuning is also performed.

Purpose, design and principle of operation of the carburetor.

A carburetor is needed to prepare the air-fuel mixture to power the engine. If the proportions in this mixture are incorrect, the motor is disrupted. If the proportion is not observed in the direction of increasing the amount of fuel, the mixture is called oversaturated, but if the fuel, on the contrary, is small. poor. Both the one and the other affect the engine’s operation not in the best way.

In different models of chainsaws, carburetors differ in design, but according to the principle of action, they are similar. A stream of air moves through the air channel at high speed. The damper blocking the channel allows you to change the speed of the air stream. Fuel through the sprayer is fed into the channel, where it mixes with the incoming air, forming a fuel-air mixture. The resulting mixture enters the engine.

The pressure in the float chamber, where the fuel is located before mixing, is almost equal to atmospheric. But a vacuum is created in the air channel, due to which the fuel is drawn into the air stream. The more the flap opens, the faster the air moves, and the amount of fuel also increases. the engine speed rises. So simplified, you can imagine the principle of the carburetor.

For efficient, smooth operation of the tool, obtaining maximum returns and at the same time economical fuel consumption, the carburetor of the chainsaw is required. Before adjustment, it is necessary to check the fuel and air filters. they must be clean. On most chainsaws, tuning is done with three screws: idle, high revs, low revs. The following signs indicate the correct carburetor setting:

  1. The chain does not idle.
  2. The engine accelerates smoothly and quickly.
  3. The sound of the running motor is even, similar to the sound of a four-stroke engine.
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The carburetor adjustment must be treated with all possible care, because errors in the settings can lead to very serious consequences, up to the occurrence of engine malfunction. If there is no absolute confidence in your abilities, you must contact the service center.

Husqvarna Saw Carb Adjustment.

For the break-in mode, so that the parts receive sufficient lubrication, the carburetor of the Husqvarna chainsaw is configured so that the maximum speed is 600–700 rpm. lower than working. If it is not possible to set the operating maximum frequency according to the tachometer, it is not worth changing the default settings with screw H. Exceeding the maximum speed value by the manufacturer is prohibited. If, after completing the adjustment, when the engine is idling, the saw chain moves, turn the screw T counterclockwise to force it to stop completely.

For precise adjustment, the saw must be warmed up for at least 10 minutes, installed on a flat surface. The tire should be pointing in the opposite direction from the person performing the tuning. At the initial stage, the highest value of the idling frequency should be detected. To do this, screw L is smoothly turned first from left to right, then vice versa. When the maximum revolutions are found experimentally, the screw L must be turned counterclockwise by a value from 1/8 to a quarter of a full revolution.

Idling is adjusted by a jet marked with the letter T. It must be turned from left to right until the chain starts to move. Then feed in the opposite direction until the chain stops spinning. The screw H is considered to be installed correctly if the noise of the saw at full throttle without load remains small. If the exhaust is too smoky and the saw is very noisy, the mixture is too rich. You need to turn the H jet clockwise until the correct sound is set. How to properly adjust the carburetor, you can see the video below.

Chainsaws Partner and Stihl, their adjustment.

In Stihl and Partner chainsaws, the proportion of air and gas in the mixture is set by adjusting screws H and L. When the screws are loosened, the mixture is enriched, rpm increases. Tightening leads to lean mixture and, consequently, lower engine speeds.

Setting the carburetor of the chainsaw Partner for idle is carried out by the T screw (Stihl marks this adjustment with the letters LA). Basic tool setup is done at the factory during the final tests. In most cases, the carburetor is adjusted to supply a slightly more enriched air-fuel mixture than the optimally calculated one. Settings set by the manufacturer must be saved in the first few hours of operation, during the break-in period. After that, finer adjustment can be carried out, although this is not necessary, the saw will work normally at the basic settings.

For fine adjustment of the carburetor, a tachometer is required, in addition, technical documentation is required to carry out work in strict accordance with the requirements of the manufacturer. The best solution is to entrust the jewelry tuning of fuel equipment to specialists.

If you decide to adjust it yourself, you should start with the screw L, then go to the jet H, and then set the idle speed by turning the screw T (or LA if it is a Stihl saw).

By smoothly turning the screw L in both directions, the position is sought at which the idle speed will be maximum. After this point is found, it is necessary to unscrew the screw L 1/4 turn. If the chain continues to move while the engine is idling, the T screw (LA) is slowly unscrewed until the chain stops.

After setting the maximum revolutions with screw H, the value of their frequency is checked by the tachometer. If the maximum speed does not correspond to the values ​​indicated in the documentation, the adjustments are repeated. If at maximum speeds the mixture is too rich, too much smoke comes out of the muffler, when the mixture is poor, the saw makes a screeching sound and the engine gets too hot. The adjustment ends with the installation of idling. the position is considered correct if the motor runs smoothly at minimum speed and the chain is standing. The idle setting can be seen in the video below.

Custom carburetor Chinese chainsaw

The standard position for carburetors of the “Chinese” is the position of the screw L, in which it is weakened by one and a half turns from the fully clamped position. For screw H, one revolution from the same state. On many videos, screw L is called adjusting the quality of the mixture, and screw H is called its quantity. Idling is regulated in the same manner as described above on a warm engine.