Adjusting the STIHL 170 carburetor. How to adjust the maximum rpm

STIHL 211 KOLHOZIM. Part 1 Adjusting the carburetor

A carburetor serves for mixing the fuel-air mixture in accordance with a pre-set ratio. If the exact doses are not respected, the engine’s serviceability is endangered. When during mixing the components a large amount of air is received, but not enough fuel, such a mixture is considered “poor”.

Over-saturation should also be avoided, as a large amount of fuel compared to air can also cause malfunction or engine wear. Adjustment of the carburetor is necessary not only before initial use, but also when any abnormalities in its operation are detected. Before you start working with your chainsaw, don’t forget to run it in.

The carburetor design contains a standard set of elements, but may vary slightly depending on the manufacturer. Components:

  • The base. This is a special tube, which visually resembles an aerodynamic construction. The air passes through it. In a transverse direction in the middle of the tube there is a damper. Its position can be changed. The more it extends into the aisle, the less air gets into the engine.
  • Diffuser. It is the narrowed part of the pipe. It is used to increase the airflow rate exactly in the segment where the fuel comes out.
  • Fuel lines. The fuel-air mix is in the float chamber, then goes to the nozzle where it comes out to the atomizer.
  • Float chamber. Is a separate constructional element, resembling the shape of a tank. Designed to maintain an optimal level of fuel fluid at all times before entering the channel from where the air enters.

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Why the spark plug fills up on a chainsaw: causes and solutions

Household and professional chainsaws are equipped with internal combustion engines that are simple in design and reliable in operation. A large proportion of drive failures are due to fuel system malfunctions. Why a spark plug fills up on a chainsaw and how to correct the problem with your own hands?

The power units that complete the entire chainsaw range operate on a precisely metered mixture of fuel and special engine oil designed to operate two-stroke engines.

In the carburetor, fuel and air are mixed in a 1:16 ratio, after which the air and gasoline emulsion is pumped into the combustion chamber.

The consequences of running an engine with an untuned fuel mixture

The mix ultimately affects the tractive power of the engine and the engine’s service life.

  • Low-mix operation causes output loss, cylinder overheating and intense wear of the chain saw’s loaded components.
  • Working with a rich mixture is no less dangerous. Trouble is manifested by longer ramp-up time, increased fuel consumption, and smoke from the muffler.
  • There is also intensive formation of soot in the combustion chamber, loss of mobility of piston rings.

Algorithm for determining the causes of poor mixture formation

In any case, a wet spark plug on a chainsaw indicates a pronounced imbalance in the composition of the fuel-air emulsion. Already with a fuel to air ratio of 1:14 conditions of spark formation worsen, the lack of air impedes proper combustion of the fuel-air emulsion compressed in the combustion chamber.

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The main causes of mixture over-enrichment in most cases are standard:

adjusting, stihl, carburetor, adjust, maximum

Risks of using low-quality fuel

Various low-octane gasolines and fuel surrogates contain alcohol components, which require more time for complete combustion. The economics of using such fuel is questionable, because there are a number of factors that confirm inefficient operation and forced engine wear.

Plug greasing is promoted by the use of heat-resistant engine oils for 4-stroke engines, heavy wear of compression rings or the entire piston group.

Troubleshooting Recommendations

In the first case, the problem is solved by bringing the air intake device. The exhausted paper filter is recommended to be blown with reversed airflow, or at best to be replaced. Cleaning methods for other filter types are explained in the accompanying owner’s manuals.

  • The carburetor is adjusted with the engine warmed up to working temperature. The power unit is brought to an optimum mode by turning the adjustment screws of quantity and quality of mixture. The success of the operation depends on the knowledge of fuel supply system design, interaction of all components.
  • In particular, the increased complexity of adjustment of carburetors with built-in compensators and other elements of automatic control. Such equipment is adjusted with special equipment, which is equipped with service and repair centers.

If the engine cannot be regulated, excessive fuel in the mixture can be caused by valve leaks or the carburettor float hangs up.

The final result of the work performed:

  • rapid revolutions;
  • stable idle mode operation;
  • recovery of traction parameters;
  • absence of excessive smoke and detonation noise.

Criteria for spark plug selection and operation

The simplest indicator of the mixture quality is a headlight insulator of the center electrode of the spark plug. Any shade of brown color indicates normal quality of the mixture, white or smoked insulator indicates poor or over-enriched composition of the emulsion.

The caliper number of the spark plug in use must meet the stated requirements.

  • The cause of oiling could be a so called “cold” spark plug, which can be visually detected by a short insulator. Interruptions in spark formation are possible if the gap is not properly adjusted or due to natural burnout of the contacts.
  • The recommended spark plug pin spacing is given in the manual, in the absence of information you can be guided by the standard value of 0.7-1 mm. A smaller gap reduces the efficiency of ignition of the fuel-air emulsion, a larger gap may lead to interruptions in spark formation.
  • Burning damp or oily spark plug on an open flame is not recommended because of the risk of cracking and premature failure.

Over-enrichment of the mixture in the combustion chamber of a technically serviceable chainsaw can be corrected by blowing out the engine. To do this, simply unscrew the spark plug and turn the crankshaft a few times with the hand starter.

Should the chainsaw be dismantled before adjustment??

Adjusting the carburetor on this unit is performed without using disassembly, sometimes remove the cover on the air filter. There is the following contradiction in the situation: on the one hand the chainsaw is supposed to perform unobstructed adjustment of the node, on the other hand it is recommended to adjust it as rarely as possible.

Workers with a lot of experience, have a screwdriver with a flat and long sting to adjust the carburetor over time.

The explanation of this fact is the following: during the assembly of the chainsaw carburetor is not particularly accurate adjustment, which is set to a certain proportion of the fuel mixture. It is clear that this factor is influenced by different conditions that differ between the work and the bench.

When changing the octane number of the gasoline or the formation of high humidity in the air, workers have a high level of experience. They in their technique know how to adjust the right mixture to get good performance and reduce wear on engine parts. But this procedure requires a lot of experience with a particular brand of chain saw and knowledge of the nuances of its work. Adjustment is considered a very fine job, the screws should be tightened very little, only 1/10 1/20 of a turn. Another reason for adjustment is to perform repair work or replace a carburetor. Adjustment of the quality of the fuel mixture is carried out, if the carburettor is undamaged and all gaskets are tight, the air filter is in clean condition and the spark plugs, clutch and ignition system are fully functional. With a faulty carburetor, chances are that the malfunction will disappear on its own over a period of time and the setting will be correct again-this will not happen. A faulty carburetor will result in an engine failure that will wear out before its time.

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Tips from the Professionals

Before adjusting the carburetor on your STIHL chain saw, inspect the spark plugs. By their condition and color you will be able to determine if the operation is necessary. If they are black in color, it indicates over-enrichment. If the color is brick gray, you can be sure that everything is normal. If there is a white deposit on the electrodes of the plug, the mixture is depleted.

It is the upper screw that plays a major role in adjusting the carburetor. It is located near the muffler. If you follow the factory settings, which can be found on the housing cover, it should be unscrewed one turn. Then it is adjusted. By unscrewing the screw you make the working mixture more enriched and more gasoline goes into it. If the screw is screwed in, the working mixture will be combined, with less gasoline in the fuel mixture.

Features of adjusting the carburetors of popular brands of chainsaws with their own hands

Despite the fact that, at first glance, all carburetors are the same, the adjustment of this unit may differ depending on the brand of the tool. The differences may be insignificant, but they are there, and it is worth mentioning.

How to adjust the carburetor of a STIHL 180 chain saw with your hands

The carburetor of the STIHL 180 chain saw is quite interesting. Its peculiarity is that there are no two of the usual three adjusting screws. That’s why adjustment of the carburetor of a STIHL 180 chain saw comes down to a simple adjustment of the idle speed with the help of a single screw LD. This is not the case with the other STIHL 250. Here the knot is almost usual, with three screws. The only difference is that the idle speed when adjusting the carburetor STIHL 250 is adjusted with the screw H, and not T.

The nuances of carburetor adjustment of “Ural” brand chainsaws

Then you should sharply pull the throttle lever. If the revolutions went up quickly, then everything is normal, you can fix the small throttle screw. If they do not grow dynamically enough, it is necessary to unscrew the full throttle screw a little. And after the run-in you can adjust the maximum power.

By the way, the same carburetor is installed on the chain-saws “TAIGA”, which means that the adjustment will be identical.

The chainsaw “Partner 350”: how to adjust the carburetor

Here it is simple. Adjustment of the carburetor of the chainsaw “Partner 350” is made according to the step-by-step instructions presented by us today. But if there is anything about it that the reader does not understand, here is another option. Below is a video of adjusting the carburetor of a “Partner 350” chainsaw, which will help to understand this issue.

Husqvarna 142: how to adjust the carburetor of this chainsaw with your own hands

And this make and model has no features or differences. All carburetor adjustments on the Husqvarna 142 chainsaw (as well as the 137 or 240 models) with their own hands are made according to the similar step-by-step instruction algorithm. This is the most common variant of adjustment, that’s why it was given in the above instruction. For example, adjustment of the carburetor of the “Carver” chainsaw is made in a similar way.

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Comparison with competitor saws

If you compare Husqvarna 236 and STIHL ms 170, then in terms of power characteristics, Husqvarna is slightly ahead. Its power is 1.4 kW, while the Stihl has 1.3. The STIHL MS 170, on the other hand, is the top fuel consumption category. к. Its engine displacement is much smaller at 30.1 cc versus the Husqvarna’s 38.2 cc.

The Husqvarna has an environmentally friendly X-Torq engine that noticeably suppresses the chainsaw’s max power. With a displacement of 38.2 cm3, the saw has to deliver a lot more power. For example, the STIHL Ls 180, with an engine displacement of 31.8 cm3 is able to deliver 1.5 kW.

Does it need to be disassembled?

Adjust the carburetor chain saw can be generally without any disassembly, in rare exceptions will only have to remove the cover of the air filter. This is where the contradiction arises: on the one hand, the chainsaw is designed for unhindered access to the adjustment mechanism, but on the other hand, it should be handled as infrequently as possible.

But experienced sawyers and woodcutters always carry a flat blade screwdriver with a long stinger and periodically adjust the carburetor. The explanation is simple: when a chainsaw is made, its carburetor is roughly adjusted for a certain composition of air and fuel. It is clear that the conditions on site are different from the bench.

If a change in gasoline brand or, for example, an increase in air humidity, an experienced chainsaw user will always adjust the mixture quality for better performance and less wear on the piston part. But this, again, requires a lot of experience with a particular chainsaw and knowledge of its behavior. Besides, the adjustment is incredibly fine. the screws are tightened only by 1/10th of a turn. 1/20 of a turn.

Another reason for adjustment is to repair or replace the carburetor. In any case, the adjustment of the mixture quality should be done only if the serviceability of the carburetor is reliably known (no garbage, gaskets don’t blow), the air filter is clean, the spark plug, clutch and ignition system are all in order. Otherwise, it is very likely that the fault will be fixed at one point and the adjustment will be abruptly wrong, and the engine will start to run out of fuel.

In order for your chainsaw to work properly, you need to carefully perform carburetor tune-ups in their exact order. If there are any irregularities in the operation of the device, you must perform a complete disassembly on your own. In most cases, any parts that have become unusable will need to be replaced.

If carburetor settings are constantly checked and measures are taken in time to improve performance, there are no problems with the chainsaw.

, What to do if chainsaws do not start and what nozzles on a chainsaw should be chosen.

Read about how to choose a chainsaw here.

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