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 the parts only after removing the piston group from the engine. The rings themselves should be tight enough and at the same time sit freely on the piston. The presence or absence of wear on the piston and rings can be verified experimentally. To do this, the piston inserted into the cylinder should be shaken slightly in different directions. Excessive piston free travel is most likely indicative of wear.
To eliminate this defect, either the cylinder is bored and the 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 absence of oil supply to the chain, as evidenced by the apparent dryness of the latter, or in oil leakage.
Lubricating fluid is either poorly or not at all supplied to the chain, as a rule, due to clogging or complete clogging of the oil supply channels. To identify 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 is 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, the repair of the Shtil chainsaw, due to the relative simplicity of its design and the fundamental similarity of its power unit with many other internal combustion engines, can be carried out on its own. Moreover, this can be done in ordinary home conditions, without resorting to the help of repair specialists.
For a small, compact chainsaw mechanism, the calm 250, the correct carburetor setting plays a key role. All well-coordinated work, all load modes and its trouble-free operation directly depend on the adjustment of the fuel supply systems, the quality and quantity of the fuel-air mixture. This article describes how to adjust the carburetor for calm 250 and set up all of its dosing systems.
In fig. 1 shows a modern carburetor for a chainsaw made in Germany “Calm 250. It is a unit the size of a half of a human fist. The movement is manufactured by Walbro, Taiwan. Case material - stainless steel alloy. At the bottom of the device, a flap is fixed, which ensures a uniform supply of the fuel-air mixture to the engine combustion chamber.
Rice. 1. Carburetor for the "Calm" chainsaw.
Holes are also made here for attaching the unit to the body of the power unit. A sealing gasket is installed between the flanges of the mixture supply and the combustion chamber of the engine. An accelerator pump is located under the throttle stem. It is a small piston with a rubber ring.
The front of the case houses a series of easy-to-use spring-loaded adjusting screws:
idle move;
maximum speed;
the amount of the mixture;
the quality of the mixture.
It is these screws that adjust the carburetor of the chainsaw calmly.
The main innovative feature of the calm 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 body during operation. For this, the unit is switched to winter operation mode.
The body is blown with heated air sucked 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 is closed.Summer mode is characterized by natural cooling of the unit.
Throughout the entire operation process, the need for additional adjustment and ensuring the correct supply of the fuel-air mixture periodically arises. How to determine exactly when and what setting needs to be done for the equipment to function normally? There are characteristic signs when the mechanism, according to the behavior of individual parts, itself suggests when adjustment is necessary.
First of all, each time before starting the engine again, it is necessary to check the color of the spark plug electrodes.
By changing it, you can make a decision about the need to adjust, adjust work processes, improve the quality of the combustible mixture:
Black electrodes covered with soot or carbon deposits indicate an over-enriched air / fuel mixture entering the engine.
Brick-gray electrodes indicate that the mixture is ideal in its composition and no additional adjustments are required.
A white coating on the spark plug electrodes indicates that the mixture is lean.
The signs described in paragraphs 1 and 3 indicate that for a calm 250 chainsaw, carburetor adjustment is extremely necessary.
NOTE! The owner may need to adjust the carburetor calm 250 with his own hands if the quality of the fuel, the height above sea level have changed, or if a vacuum occurs at the place of operation of the chainsaw. It is possible that the air humidity, temperature, atmospheric pressure have changed.
Precise settings will allow you to achieve maximum performance of the unit while reducing the external necessary conditions 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 the lean air-fuel mixture.
Of paramount importance in setting all the characteristics of the fuel dosage of the calm 250 model is the uppermost adjusting screw located near the muffler. The factory setting, the parameters of which are shown on the upper plastic cover, provides that it should be unscrewed one turn from full twist.
Throughout the operation process, the carburetor of the chainsaw calm 250 is adjusted with your own hands. Unscrewing the screw makes the working mixture richer, since the air-fuel mixture receives more gasoline, and tightening the screw makes the working mixture leaner, since the air-fuel mixture receives less gasoline.
Carburetor adjustment will not give positive results if air is leaking from the engine side through:
carburetor gasket;
rubber ring of the accelerating pump;
crankshaft oil seals.
Calm 250 carburetor adjustment is carried out only after a careful examination, identifying existing air leaks. The next stage of preparatory commissioning is full maintenance of all units and mechanisms.
cleaning from deposits, slags, resins;
washing the engine using a solvent, acetone;
replacement of the spark plug;
cleaning, washing the air filter;
checking the tension of the cutting chain;
idle setting;
warming up the engine to operating temperature.
Then you can start complex manipulation of the settings.
Rice. 2. Adjustment of the Stihl 250 chainsaw carburetor.
Step-by-step adjustment of the Shtil MC 250 carburetor with a revolution counter is carried out in the following sequence:
Switch off the engine, screws H and L should be tightened up to the stop, then unscrew both one turn.
Start the engine, warm it up. At maximum speed with screw H, achieve a maximum crankshaft frequency of 14,000 rpm, recorded by a tachometer or an engine revolution counter. Hold the maximum engine speed for no more than 10 seconds.
Using the bolt LA of the idle speed stop, achieve the start of the chain movement.Then turn bolt LA ¼ turn counterclockwise.
Check the acceleration of the Stihl 250 chainsaw mechanism. The 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 speed. Make final adjustments with the LA screw. According to the tachometer, the idle speed must correspond to the catalog value of 2800 rpm.
Similarly, do-it-yourself adjustment of the Stihl 211 chainsaw carburetor.
In his article, the author highlighted in as much detail as possible all the details of adjusting the familiar mechanism made in Germany called the Stihl 250 saw. Adjusting the carburetor is simple and accessible to every home craftsman. Following the recommendations set out by the author of the article, everyone can set up their Stihl 250 chainsaw and enjoy its flawless operation.
Engine oil for STIHL 2-stroke engines 1:50:
1:50 = 1 part oil + 50 parts gasoline
other branded motor oils for two-stroke engines of vehicle classification:
1:25 = 1 part oil + 25 parts gasoline
Examples of fuel mixture ratios:
Chainsaw Calm is a tool that is designed for harvesting wood, processing plants, creating landscaping and other household needs. In the event of a breakdown of any parts or failure of the device, 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 arise in the components and design of the device, and how to repair the Stihl 180 chainsaw with your own hands.
If you notice that Calm is pouring a candle on the 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 lean, then there is a decrease in power, the cylinder overheats and the saw systems wear out. A wet plug on a Stihl chainsaw is due to a disproportionate fuel mixture. Lack of air in the mixture prevents correct combustion of the emulsion.
The use of low quality gasoline can lead to engine wear.
Oil plugging of the spark plug also causes the use of oil for 4-stroke engines and piston wear. If such a malfunction occurs, it is necessary to remove the gas tank cap and adjust the fuel supply. The air intake should be repaired. The clogged filter must be blown out with air, or it is better to replace it. How you can clean the filters is described in the instruction manual for the chainsaw.
It will be possible to determine the quality of the mixture using a spark plug insulator. If a brown color appears on it, 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 candle is the cause of oiling. Interruptions in spark formation are observed when the gap is incorrectly set. In the instructions for the repair and operation of the device, the distance between the contacts of the spark plug 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 interruptions in the formation of a spark occur. To eliminate the over-enrichment of the mixture, the motor is purged. In this case, you need to remove the candle and turn the crankshaft several times with a manual starter.
When repairing a chainsaw, you will notice that no oil gets 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 in color.
The chain stretches too quickly.
The tire is too hot and the paint has melted on it.
Oil does not drain in the tank.
With a sharp chain, the saw has become worse to cut.
Such signs indicate that there has been a violation of the lubrication process. To check the oil supply to the lubrication unit, you need to remove the tire and turn on the chainsaw. Then increase the speed and observe the end point of the oil line. If the oil is running, it means that its volume is not enough for proper lubrication. If there is no supply, you need to clean the filter. You should also adjust the oil flow. In the absence of malfunctions, further diagnostics and do-it-yourself repairs are required. If it turns out that the substance is not being supplied, then the oil system is repaired.
Consider the main malfunctions and methods for their elimination:
Broken oil hose. This can be seen on examination. In this case, the hose must be replaced.
If there is no thread on the shaft of the oil pump, then it should be replaced.
If there are defects in the thread, then it must be replaced.
If there is no main shaft corkscrew, then a nail of the same diameter can be installed in its place.
The filter might be clogged. This happens frequently with the Stihl MS 180. You can wash it off 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 from the tank is inserted into the tool body. A breakdown can be detected by oil leaks at the bottom of the saw.
To fix the problem, you need to remove the saw handle, pull out the hose. After that, you need to clean the hose. Then apply sealant to it and place it in the tool body.
If the chainsaw does not start, then the cause may be a breakdown of the ignition and engine start unit. If, when measuring the gap between the module and the flywheel, no deviations are found, then the spark plug should be checked. It is pulled out of the shaft 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 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 fuel hose.
Clean the filter.
Check the quality of gasoline and oil.
Check the operation of the carburetor and spark plugs.
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;
unbalanced carburetor screws.
If, after testing, no defects are found, then the carburetor is checked.
In order to repair the device, it must first be disassembled. You need to remove the side cover, saw chain and bar. Then clean the instrument, blow it out with a compressor and clean all the assemblies with a brush. Then remove the handle. To do this, remove the plugs from the shock absorbers using 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. The part is removed. Then remove the flywheel by unscrewing the nut that holds it, unscrew the flywheel nut. You need to twist to the left. Remove the flywheel. Then dismantle the clutch, oil pump drive and carburetor.
After that, the motor is removed and disassembled. It is held in place by 4 screws on the bottom of the saw. You need to unscrew them and remove the motor. Then the engine itself is disassembled. Unscrew the crankcase screws, remove it. Then dismantle the crankshaft, oil seals, bearings and piston rings. At the end of the disassembly, repairs and troubleshooting are performed.
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 there will be the side of the crankshaft in which you want to mount the flywheel. They put the piston in the cylinder. Install the bearings, oil seals and circlip into the cylinder.After that, degrease the place of fixing the crankcase and install it in its place. When reassembling, follow the reverse sequence for dismantling.
Remove the drive sprocket before unscrewing the clutch. Remove the corkscrew washer and remove the sprocket and needle bearing. Unscrew the clutch. Remove the baffle plate and pump.
Chainsaw sprocket replacement is needed when:
jams the movement of the chain;
the drive sprocket has 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.
Consider how to change the oil pump. If the element leaks, then the gasket between the two parts should be renewed. If this part of the oil pump is not damaged, then it must be wiped and put back. Now they check the hose. There should be no cracks on it. If the hose is damaged, replace it. Then the outlet channels are cleaned with a compressor.
Let's consider how the diagnostics 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, unscrew the pallet, remove the crankshaft with the piston from the cylinder. Unscrew the piston pin stoppers. 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, the piston is lubricated with oil. Before installing the crankcase, degrease its surface and apply a sealant.
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.
The carburetor is adjusted on a warm engine. If the engine fails to tune, the carburetor stuck could be the cause of 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.
VIDEO
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. At the Stihl saw, the carburetor has 1 idle speed 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.
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, it must be replaced.
It would seem, why does a chainsaw need a summer resident who grows vegetables and fruits, or the owner of a country house who has a small garden and several flower beds? The question disappears when there is a desire to build a bathhouse, update a greenhouse, topple an old business, or just make a bench for relaxation. Unfortunately, any mechanism periodically needs preventive maintenance and replacement of spare parts, and for this you need to be well versed in the device of the product, besides, repairing the chainsaw with your own hands will save time and money.
All chainsaws are similar in structure, regardless of whether they are European (ECHO, Stihl, Husqvarna) or domestic (Kedr, Ural). The main elements are located inside the body - the fuel tank and the engine, and outside the starter, the handle, the saw part (tire) with the chain. A sharp jerk in the cable starts the engine, which starts the saw blade.
To begin with, we suggest that you familiarize yourself with the video clips that show how the chainsaw works and how it works:
From time to time, the saw malfunctions, which require disassembly to eliminate. What can happen to such a simple mechanism as a chainsaw? At least the following:
Stops getting started;
Starts up, but soon stops;
Ceases to function in the cut;
Loses its power;
Most of the malfunctions 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 assemblies (clutch, chain brake, tire, lubrication system). Let's consider the most common breakdowns and techniques for their elimination.
A serviceable chainsaw starts with one jerk and does not fail in the cut
The first thing to do if a chainsaw breaks down is to inspect the spark plug by disconnecting the wire and carefully unscrewing it with a special key.
Components of the chainsaw ignition system: 1 - flywheel with magnets, 2 - ignition module, 3 - spark plug, 4 - high voltage wire
Unscrew the spark plug to check its condition.
Her appearance says a lot:
Dry. Most likely, the fuel mixture does not enter the cylinder. It's not about the ignition system, so the plug is screwed back in.Strongly splashed with fuel. The reason for the excess fuel mixture lies either in the violation of the starting rules, or in the incorrect adjustment of the carburetor. Carefully wipe the spark plug, shut off the fuel supply and turn on the starter to remove excess fuel and ventilate the combustion chamber. Then the candle is put in place and the mechanism is started again.Covered with black carbon. This may indicate the use of low-quality oil, an incorrectly adjusted carburetor, or an incorrectly calculated gasoline to oil ratio. The candle should be washed, cleaned of carbon deposits with a sharp object (awl or needle), wipe the electrodes with a sandpaper and put in place.When checking the candle, you need to pay attention to the gap between the electrodes: it is considered normal from 0.5 to 0.65 mm. A damaged or worn gasket must be replaced.
A large amount of black carbon on the spark plug indicates a malfunction of the engine.
To be sure, you should also check for a spark. To do this, put the ignition cable on the spark plug, connect the plug nut and the cylinder with pliers, start the starter and watch for the spark. If it is missing, the plug must be replaced. If the new spark plug also does not emit sparks, the problem is in the high-voltage wire or in the broken connection with the spark plug.
Fuel may not enter the cylinder for the following reasons:
Dirty fuel filter. 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). It is also checked by disconnecting the hose, in case of blockage, clean it with a needle.Lack or insufficient amount of fuel. There may be several reasons for the malfunction. The first reason is a clogged air filter. Air ceases to flow into the carburetor in the required amount, in this regard, due to a too rich fuel mixture, engine operation is disrupted. The contaminated filter is carefully removed, cleaned and washed in water, then dried and reinstalled.Another reason is improper adjustment of the carburetor. The adjustment is made with three screws.
Timely replacement of the fuel filter ensures full fuel supply
The fuel hose and choke actuator must fit snugly on the fittings
The throttle lever cable must be in place
During work, you must use the instructions, otherwise you can only make it 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 parts.
All parts must be clean, dry and in good condition.
If the engine works fine at low speeds, and at high speeds it starts to stall, the reason may lie in the spark arrester of the muffler, clogged with combustion products.
remove the muffler;
disassemble (there are also non-separable models);
remove carbon deposits using detergents;
dry with a hairdryer;
install in place.
Dry cleaning is unacceptable, as the soot contains carcinogens, the inhalation of which is hazardous to health. After removing the muffler, cover the outlet with a clean cloth.
Interruptions in the operation of the chainsaw signal a possible clogging of the muffler
To avoid clogging of the muffler, it is necessary to monitor the composition of the fuel mixture. The amount of oil should not exceed the rates recommended by the manufacturer. Poor oil quality also negatively affects engine performance.
Often the engine will not start or run at full capacity due to low cylinder pressure. It can be caused by piston or cylinder wear, piston ring sinking, bearing wear. You can partially examine the state of the cylinder-piston group (CPG) by removing the muffler and looking into the opened hole.
A compressor placed in the plug hole will help to measure the compression in the engine - according to the measurement results, you can also talk about the state of the CPG. Accurate data is obtained only after complete disassembly of the mechanism. If the piston is chipped or scratched, it must be replaced. The piston ring must be clean, free of carbon deposits, and be exactly in place.
Piston and crank mechanism wear is considered a serious problem.
According to the results of measuring the compression, one can judge the condition of the parts of the CPG
Let's consider three main faults:
Oil leakage. Check that the pipes are tightly connected to the pump unions and that they are not cracked. Problem tubes are sealed with sealant or replaced.
Insufficient oil supply. Most likely, the lubrication passages are clogged.
Cracks in the oil pump housing. Part needs to be replaced.
Here's how to diagnose the lubrication system:
The chain brake often does not work due to the clogging of grease or sawdust in the brake band and the space under the cover. All parts should be cleaned from blockages. Perhaps the tape is simply worn out, then it needs to be replaced.
The chain brake is restored by mechanical cleaning
Video (click to play).
Some parts of a chainsaw will wear out faster than others. These include the drive sprocket, tire, chain, anti-vibration elements. For quick replacement, it is best to always have spare parts on hand. Sharpening the chain should not be neglected.
