Of great importance for ensuring optimal pressure in the combustion chamber is the absence of signs of wear on the piston housing and piston rings. The normal functioning of the chainsaw engine largely depends on this.
It is possible to find out the degree of wear of parts only after removing the piston group from the motor. The rings themselves should be tight enough and at the same time sit freely on the piston. The presence or absence of wear of the piston and rings can be verified experimentally. To do this, the piston inserted into the cylinder should be slightly swung in different directions. Too much free play on the piston is most likely a sign of wear.
To eliminate this defect, either the cylinder is bored and repair parts are installed, or the entire CPG set is changed. Otherwise, the chainsaw will not develop the required power.
Chainsaw repair is also required if there are problems with the lubrication system. Most often they consist in the lack of oil supply to the chain, as evidenced by the obvious dryness of the latter, or in oil leakage.
The lubricating fluid either poorly or does not enter the chain at all, as a rule, due to clogging or complete clogging of the oil supply channels. To identify the places where the oil flow is blocked, it is necessary to carefully inspect the oil hose and its connection points. In addition, be sure to clean the oil filter.
VIDEO
If oil leaks, then this indicates a violation of the tightness of the oil channels or hose. As a rule, this happens due to mechanical damage. Most often, the unusable hose is removed, and a new one is put in its place. But sometimes a less radical method is used, treating the damaged hose with an appropriate sealant.
Thus, due to the relative simplicity of its design and the fundamental similarity of its power unit with many other internal combustion engines, the repair of the Shtil chainsaw can be done on its own. Moreover, this can be done in normal home conditions, without resorting to the help of repairmen.
For a small compact mechanism of a Stihl 250 chainsaw, the correct setting of the carburetor plays a key role. All well-coordinated work, all load modes and its trouble-free operation directly depend on the adjustment of fuel supply systems, the quality and quantity of the fuel-air mixture. This article describes how to adjust the Stihl 250 carburetor and set up all of its dosing systems.
On fig. 1 shows a modern carburetor for a chainsaw made in Germany “Calm 250”. It is a node the size of half a human fist. The mechanism is manufactured by Walbro, Taiwan. Body material – stainless steel alloy. A damper is fixed at the bottom of the device, which ensures a uniform supply of the fuel-air mixture to the engine combustion chamber.
Rice. 1. Carburetor for chainsaw "Calm".
Holes for attaching the assembly to the body of the power unit are also made here. A sealing gasket is installed between the flanges of the mixture supply and the combustion chamber of the engine. The accelerator pump is located under the throttle valve. It is a small piston with a rubber ring.
On the front of the case is a series of easy-to-use spring-loaded adjustment screws:
idle move;
maximum speed;
the amount of the mixture;
mixture quality.
The carburetor of the Stihl chainsaw is adjusted with these screws.
The main innovative feature of the Stihl 250 chainsaw carburetor is the heating device. In order to avoid freezing of the mechanism during operation during the winter period, it is equipped with a special system that preheats the steel case during operation. To do this, the unit is transferred to the winter mode of operation.
The body is blown with heated air drawn in from the engine. This mode of operation of the mechanism prevents icing, freezing of the jets, and ensures the normal supply of the fuel-air mixture. When switching to summer operation, the hot air damper closes.Summer mode is characterized by natural cooling of the unit.
Throughout the operation process, periodically there is a need for additional adjustment and ensuring the correct supply of the fuel-air mixture. How to determine exactly when and what settings need to be performed for the normal functioning of the equipment? There are characteristic signs when the mechanism, according to the behavior of individual parts, itself tells you when adjustment is necessary.
First of all, each time before the next start of the engine, it is necessary to check the color of the spark plug electrodes.
By changing it, a decision can be made on the need for adjustment, adjustment of work processes, improvement of the quality of the combustible mixture:
Black electrodes covered with soot or soot indicate a re-enriched air-fuel mixture entering the engine.
Brick gray electrodes indicate that the mixture is ideal in composition and no additional adjustments are required.
White coating on the spark plug electrodes indicates that the mixture is lean.
The signs set out in paragraphs 1 and 3 indicate that for a Stihl 250 chainsaw, carburetor adjustment is essential.
NOTE! Do-it-yourself adjustment of the Stihl 250 carburetor may be necessary for the owner if the quality of the fuel, the altitude above sea level have changed, or if there is a rarefaction at the place where the chainsaw is used. Perhaps the humidity, temperature, atmospheric pressure has changed.
Precise settings will allow you to achieve maximum performance of the unit while reducing the external conditions necessary for its operation. Successful debugging of operating conditions prevents oil starvation and engine failure due to insufficient lubrication. After all, the lubricant enters the saw cylinder along with a lean fuel-air mixture.
Of paramount importance when setting all the characteristics of the fuel dosage of the Stihl 250 model is the uppermost adjusting screw located near the muffler. The factory setting, the parameters of which are shown on the top plastic cover, provides that it should be unscrewed one turn from full twist.
Throughout the operation process, the carburetor of the Stihl 250 chainsaw is adjusted by hand. Turning the screw out richens the mixture because the air-fuel mixture receives more gasoline, and turning the screw leans the mixture because the air-fuel mixture receives less gasoline.
Adjusting the carburetor will not give positive results if there is air leakage from the engine side through:
carburetor gasket;
accelerator pump rubber ring;
crankshaft seals.
Setting up the Stihl 250 carburetor is carried out only after a careful examination, identifying existing air leaks. The next stage of preparatory adjustment work is the full maintenance of all components and mechanisms.
cleaning from deposits, slags, resins;
washing the engine using a solvent, acetone;
spark plug replacement;
cleaning, washing the air filter;
checking the tension of the cutting chain;
idle setting;
warming up the engine to operating temperature.
Then you can proceed to complex configuration manipulations.
Rice. 2. Adjusting the carburetor of the Stihl 250 chainsaw.
Step-by-step adjustment of the Stihl MS 250 carburetor with a revolution counter is carried out in the following sequence:
Stop the engine, screws H and L should be tightened to the stop, then both should be unscrewed by one turn.
Start engine, warm up. At maximum speed, use screw H to achieve a maximum crankshaft speed of 14,000 rpm, recorded by a tachometer or engine speed counter. Hold the maximum engine speed for no more than 10 seconds.
Use the idle stop bolt LA to start the chain movement.Then turn the bolt LA ¼ turn counterclockwise.
Check the acceleration of the Stihl 250 chainsaw mechanism. Carburetor adjustment continues if the idle speed is unstable or the chainsaw does not accelerate enough. Screw L must be turned slightly counterclockwise. At the same time, the saw should quickly gain momentum, function stably at idle. Finally correct the work with the LA screw. According to the tachometer, idling should correspond to the catalog value of 2800 rpm.
Similarly, the carburetor of the Stihl 211 chainsaw is adjusted by hand.
In his article, the author covered in as much detail as possible all the details of adjusting the familiar German-made mechanism called the Stihl 250 saw. Carburetor adjustment is simple and accessible to every home master. By following the recommendations outlined by the author of the article, everyone can set up their Stihl 250 chainsaw and enjoy its flawless performance.
Engine oil for two-stroke engines STIHL 1:50:
1:50 = 1 part oil + 50 parts gasoline
other branded motor oils for two-stroke engines of TC classification:
1:25 = 1 part oil + 25 parts gasoline
Examples of fuel mixture ratios:
The Stihl chainsaw is a tool that is designed for harvesting wood, processing plants, creating landscape design and other household needs. If any parts break down or the device fails, you will need to repair the Stihl chainsaw.
The chainsaw must be used according to the operating instructions, then it will last a long time and will not fail. All possible malfunctions of the Stihl chainsaw can be identified and eliminated independently. Consider the main problems that may occur in the components and design of the device, and how the Stihl 180 chainsaw is repaired with your own hands.
If you notice that a candle is pouring on a Stihl chainsaw, then a malfunction may have occurred in the fuel system. The engine must run on a mixture of gasoline and oil. If the mixture is poor, then there is a decrease in power, the cylinder overheats and the saw systems wear out. A wet spark plug on a Stihl chainsaw is due to an imbalance in the fuel mixture. The lack of air in the mixture prevents proper combustion of the emulsion.
The use of low-quality gasoline can lead to engine wear.
Clogging of the spark plug also causes the use of oil for 4-stroke engines, wear of the pistons. If such a malfunction occurs, it is necessary to remove the gas tank cap and adjust the fuel supply. The air intake must be in good condition. A clogged filter must be blown out with air, but it is better to replace it. How to clean the filters is described in the chainsaw operating instructions.
It will be possible to determine the quality of the mixture using a candle insulator. If a brown color appears on it, then this means that the quality of the mixture is normal. White color or soot indicates a poor or over-enriched composition of the mixture.
The cause of oiling is a candle. Interruptions in the formation of a spark are observed when the gap is set incorrectly. In the instructions for the repair and operation of the device, the distance between the contacts of the candle is given. If you do not have such data, then you can set 0.7-1 mm.
If the gap is smaller, then the efficiency of ignition of the mixture decreases, if it is larger, then there are interruptions in the formation of a spark. To eliminate the over-enrichment of the mixture, purge the motor. In this case, it is necessary to remove the candle and turn the crankshaft several times with a manual starter.
When repairing a chainsaw, you may notice that oil does not get on the chain. If the chain is not lubricated, then there are interruptions in the lubrication system. There are such malfunctions:
The chain is dry, light shade.
The chain stretches too fast.
The tire is too hot and the paint has melted on it.
The tank does not lose oil.
With a sharp chain, the saw began to cut worse.
Such signs indicate that there have been violations of the lubrication process. To check the oil supply to the lubrication unit, you must remove the tire and turn on the chainsaw. Then increase the speed and observe the end point of the oil line. If oil flows, it means that its volume is not enough for proper lubrication. If there is no supply, the filter must be cleaned. You should also adjust the oil supply. In the absence of malfunctions, further diagnostics and do-it-yourself repairs are required. If it turns out that the substance is not supplied, then the oil system is repaired.
Consider the main malfunctions and methods for their elimination:
Oil hose break. This can be seen upon inspection. In this case, the hose must be replaced.
If there is no thread on the oil pump shaft, then it should be replaced.
If there are defects in the thread, then it must be replaced.
If the corkscrew of the main shaft is missing, then a nail of the same diameter can be installed in its place.
The filter may be clogged. With the Stihl MS 180 saw, this happens often. You can wash it with gasoline. If this does not correct the problem, the filter should be replaced.
The Stihl 180 chainsaw often has a depressurization of the oil line. This occurs where the oil line coming from the tank is inserted into the body of the tool. You can detect a breakdown by smudges of oil at the bottom of the saw.
To fix the problem, you need to remove the handle of the saw, pull out the hose. After that, you need to clean the hose. Then apply sealant on it and put it in the tool body.
If the chainsaw does not start, then the cause may be a breakdown of the ignition and engine start assembly. If no deviations are found when measuring the gap between the module and the flywheel, then the spark plug should be checked. It is pulled out of the mine and the gap is measured. If fuel enters the combustion chamber, and there are no breakdowns in the ignition system, then the carburetor is faulty.
If the saw does not maintain idle speed, then the following may have occurred:
filter clogging;
violation of the ignition system;
the carburetor has deteriorated;
deformed parts of the motor.
For self-repair, you need to perform the following 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.
When Stihl chainsaws are repaired, they will work properly.
If the saw does not gain momentum, then this could lead to:
faulty engine;
cylinder wear;
failure of piston rings;
breakdown of the spark plug;
coil failure;
unbalanced carburetor screws.
If no defects are found after testing, then the carburetor is checked.
To repair the device, it must first be disassembled. You need to remove the side cover, saw chain and bar. Then clean the tool, blow it with a compressor and clean all the nodes with a brush. Then the handle is removed. To do this, remove the plugs from the shock absorbers with a screwdriver. After that, remove the shock absorbers and the handle.
Then the starter is removed. Remove the housing cover and unscrew the starter screws. Extract the detail. Then remove the flywheel by unscrewing the nut that holds it, unscrew the flywheel nut. You need to turn to the left. Take off the flywheel. Then the clutch, oil pump drive and carburetor are dismantled.
After that, the motor is removed and disassembled. It is held on by 4 screws on the bottom of the saw. You need to unscrew them and remove the motor. Then the engine is disassembled. Unscrew the crankcase screws, remove it. Then the crankshaft, oil seals, bearings and piston rings are dismantled. Upon completion of disassembly, repairs and troubleshooting are carried out.
After repair, the tool will need to be reassembled. To do this, install the piston on the connecting rod. The arrow on it should look along the chain, and to the left of the piston will be the side of the crankshaft into which you want to mount the flywheel. Put the piston in the cylinder. Install the bearings, seals and circlip into the cylinder.After that, the place of fixation of the crankcase is degreased and installed in its place. When assembling, follow the reverse sequence of dismantling.
Before unscrewing the clutch, you need to remove the drive sprocket. Remove the lock washer and remove the sprocket and needle bearing. Unscrew the clutch. Remove the reflective plate and pump.
Replacing an asterisk on a chainsaw is needed in cases where:
jamming the movement of the chain;
the drive sprocket has worn out.
To replace, you need to remove the chainsaw sprocket. The teeth of the sprocket must not deviate from the required dimensions, otherwise the saw will be accompanied by vibration, which will lead to breakage of the crankshaft and bearings. The service life of the sprocket is 2 times the working life of the chain. Use 2-3 chains until their cutting surface is abraded. After that, change the asterisk. It is located behind the clutch. Remove the clutch assembly cover.
Remove the bar, chain and clutch. But first you need to fix the crankshaft. Then the puller is placed in the hole of the coupling and rotated clockwise. Take off the clutch. Behind it is an asterisk. Now it is being dismantled. If it is defective, it is replaced.
Consider how to change the oil pump. If the element is leaking, then the gasket between the two parts should be updated. If this part of the oil pump is not damaged, then it must be wiped and put in place. Now check the hose. It should not have cracks. If the hose is damaged, replace it. Then the outlet channels are cleaned with a compressor.
Consider how the diagnosis and replacement of the piston group is carried out. It is necessary to check the condition of the cylinder and the degree of wear of the piston. After dismantling the motor, the pan is unscrewed, the crankshaft with the piston is removed from the cylinder. Loosen the piston pin locks. If the piston is defective, it must be replaced. Retaining rings are fixed with a cut down. Before installing the piston group in the cylinder, lubricate the piston with oil. Before mounting the crankcase, its surface is degreased and a sealant is applied.
It is necessary to set the ignition on the chainsaw. The ignition is adjusted as follows:
unscrew the candle and evaluate its appearance;
specify the distance between the magnets and the coil (up to 0.2 mm);
check spark.
Carburetor adjustment is carried out on a warm engine. If the engine cannot be tuned, then the cause of excess gasoline in the mixture may be a stuck carburetor. To remove the part, unscrew the fastening nuts, disconnect the ignition and thrust from the engine control lever. Then remove the lever. You can then remove the filter and carburetor.
VIDEO
The muffler is fixed with two nuts. You need to unscrew them and pull the muffler towards you. Then unscrew the screws of the coil and dismantle it. At the Stihl saw, the carburetor has 1 idle adjustment screw. If the idle speed is disturbed, then the carburetor needs to be repaired. This is a complex process, it is difficult to do it yourself. You should contact the repair shop.
Remove the side cover. Inspect the inside of the protective cover. If there is no damage, check the launch site. 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 wears out over time. If it is damaged, cracked or torn, it must be replaced.
It would seem, why would a summer resident who grows vegetables and fruits need a chainsaw, or an owner of a country house with a small garden and several flower beds? The question disappears when there is a desire to build a bathhouse, renew a greenhouse, knock down an old business, or simply make a bench for relaxation. Unfortunately, any mechanism periodically needs maintenance and replacement of spare parts, and for this you need to be well versed in the design of the product, in addition, repairing a chainsaw with your own hands will save time and money.
All chainsaws are similar in structure, regardless of whether they are made in Europe (ECHO, Stihl, Husqvarna) or domestic (Kedr, Ural). The main elements are located inside the body - a fuel tank and an engine, and outside the starter, a handle, a saw part (tire) with a chain. A sharp jerk of the cable starts the engine, and that one starts the saw blade.
To get started, we suggest that you familiarize yourself with the video clips that show how the chainsaw is arranged and how it works:
From time to time, malfunctions occur in the operation of the saw, which require disassembly to eliminate. What can happen to such a simple mechanism as a chainsaw? At least the following:
Stops starting;
Starts, but soon stops;
Ceases to function in the cut;
Loses its power;
Most of the problems are associated either with interruptions in the operation of the engine (fuel supply system, exhaust system, ignition, cylinder-piston part), or with malfunctions of other systems and components (clutch, chain brake, tire, lubrication system). Consider the most common breakdowns and methods for their elimination.
A serviceable chainsaw starts with one jerk and does not fail in cutting
The first thing to do when a chainsaw breaks down is to inspect the spark plug by disconnecting the wire and carefully turning it out with a special key.
Components of the chainsaw ignition system: 1 - flywheel with magnets, 2 - ignition module, 3 - candle, 4 - high voltage wire
The spark plug is unscrewed to check its condition.
Her appearance says a lot:
Dry. Most likely, the fuel mixture does not enter the cylinder. It's not the ignition system, so the candle is twisted back.Heavily splashed with fuel. The reason for the excess fuel mixture lies either in violation of the rules for starting, or in improper adjustment of the carburetor. The candle is thoroughly wiped, the fuel supply is turned off and the starter is turned on - to remove excess fuel and ventilate the combustion chamber. Then the candle is placed in place and the mechanism is started again.Covered with black soot. This may indicate the use of low-quality oil, an incorrectly adjusted carburetor, or an incorrectly calculated ratio of gasoline and oil. The candle should be washed, cleaned of soot with a sharp object (awl or needle), wipe the electrodes with a sandpaper and place in place.When checking the candle, you need to pay attention to the gap between the electrodes: from 0.5 to 0.65 mm is considered normal. A damaged or worn gasket must be replaced.
A large amount of black soot on the spark plug indicates a malfunction in the engine
To be completely sure, you should also check for the presence of a spark. To do this, put an ignition cable on the spark plug, connect the spark plug nut and the cylinder with pliers, start the starter and watch for a spark. If it is missing, the spark plug needs to be replaced. If the new spark plug doesn't spark either, the problem is with the high-voltage wire or a loose connection to the spark plug.
Fuel may not enter the cylinder for the following reasons:
Fuel filter dirty. Remove the fuel hose and check how the fuel flows. If the jet is weak, the filter may need to be cleaned. It is taken out through the filler hole of the fuel tank and cleaned; in case of severe contamination, it is replaced with a new one. As a preventive measure, it is recommended to replace the fuel filter every three months.Clogged breather (holes in the fuel tank cap). They also check by disconnecting the hose, in case of blockage, clean with a needle.No or insufficient fuel. There may be several reasons for the failure. The first reason is a clogged air filter. The air stops flowing into the carburetor in the right amount, in connection with this, due to an overly enriched fuel mixture, engine operation is disrupted. The dirty filter is carefully removed, cleaned and washed in water, then dried and replaced.Another reason is the incorrect adjustment of the carburetor. Adjustment is made with three screws.
Timely replacement of the fuel filter guarantees a full supply of fuel
The fuel hose and the air damper actuator must fit snugly against the fittings
Throttle lever cable must be in place
During operation, you must use the instructions, otherwise you can only make things worse.
And the last reason is a violation of the integrity of the membrane or clogging of the carburetor channels.
To repair the carburetor yourself, you need to get acquainted with all its details
All parts must be clean, dry and in good condition.
If the engine runs fine at low speeds, but starts to stall at high speeds, the reason may lie in the muffler spark arrester, clogged with combustion products.
remove muffler;
disassemble (there are also non-separable models);
clean from soot using detergents;
dry with a hair dryer;
put in place.
Dry cleaning is unacceptable, as carbon deposits contain carcinogens, the inhalation of which is dangerous to health. After removing the muffler, cover the outlet with a clean cloth.
Interruptions in the operation of the chainsaw signal a possible clogged muffler
To prevent clogging of the muffler, it is necessary to monitor the composition of the fuel mixture. The amount of oil should not exceed the norms recommended by the manufacturer. Poor oil quality also negatively affects engine performance.
Often the engine does not start or does not run at full capacity due to low cylinder pressure. It can be caused by worn pistons or cylinders, slipped piston rings, or worn bearings. You can partially examine the state of the cylinder-piston group (CPG) by removing the muffler and looking into the opened hole.
A compression gauge placed in the spark plug hole will help measure the compression in the engine - based on the results of the measurement, one can also talk about the state of the CPG. Accurate data is obtained only after the complete disassembly of the mechanism. If the piston has chips or scratches, it must be replaced. The piston ring must be clean, free of carbon deposits, and in exactly the right place.
Wear of the piston and crank mechanism is considered a serious problem
Based on the results of measuring compression, one can judge the condition of parts of the CPG
Consider three main faults:
Oil leakage. It should be checked whether the tubes are hermetically attached to the pump fittings and whether they are cracked. Problematic tubes are sealed with sealant or changed.
Insufficient oil supply. Most likely, the lubrication channels are clogged.
The occurrence of cracks in the oil pump housing. A part needs to be replaced.
Here is how the lubrication system is diagnosed:
The chain brake often does not work due to grease or sawdust clogging the brake band and the space under the cover. All parts must be cleared of blockages. Perhaps the tape is simply worn out, then it needs to be replaced.
The operation of the chain brake is restored by mechanical cleaning
Video (click to play).
Some chainsaw parts wear out faster than others. These include the drive sprocket, tire, chain, anti-vibration elements. For quick replacement of spare parts, it is better to always have at hand. Do not neglect the sharpening of the chain.
