Arrow on the piston of a two.stroke engine where to put a chainsaw

The heart of any chainsaw is an internal combustion engine that sets the working element. a sawing chain. During the operation of a garden tool, there is a need to disassemble the engine. This can be planned maintenance, cleaning from soot and soot, elimination of malfunctions or replacing nodes. If for this you will take the chainsaw to the service center, then you will not have any questions. However, with independent maintenance of a gasoline engine of a garden tool, the question often arises: how to correctly install the pistons back and where the arrow indicates them.

The heart of any chainsaw is an internal combustion engine that sets the working element. a sawing chain. During the operation of a garden tool, there is a need to disassemble the engine. This can be planned maintenance, cleaning from soot and soot, elimination of malfunctions or replacing nodes. If for this you will take the chainsaw to the service center, then you will not have any questions. However, with independent maintenance of a gasoline engine of a garden tool, the question often arises: how to correctly install the pistons back and where the arrow indicates them.

The algorithm for determining the malfunction

The reason for the refusal of the saw or the deterioration of its performance may be:

  • a clogged battleship cover;
  • Air sucker with a carburetor due to the destruction of the gasket or weakening of threaded fasteners;
  • Mechanical sequel of removable saw equipment and other minor defects.

Before starting disassembly, you should verify the need for a more volumetric repair.

Independently assemble a new chainsaw after repair with initial quality, most likely it will not be possible. In the design of modern chainsaws, press plantings of conjugated parts are often used, which have minimal maintainability.

Even a partial analysis of a chainsaw with an improvised tool can lead to undesirable consequences. In most cases, to eliminate a malfunction, you can limit yourself to the dismantling of a separate node or system.

The design of the chainsaw

Basically, all chainsaws are equipped with a two.stroke carburetor engine with one cylinder and air cooling. The stability of the work directly depends on the carburetor preparing the fuel-air mixture. The air entering the engine should not contain dust and other impurities clogging it, otherwise the piston group will wear out quickly enough.

In order to avoid this, the air filter in the chainsaw must be regularly cleaned. So that it is less likely to clog, it has a mechanism for preliminary air purification.

The engine starts with a starter (a cable with a handle wound on a pulley). Modern, even low.power saws are equipped with facilitating mechanisms. These include:

  • Primer. reducing the number of empty revolutions of the pump, pre.pumping fuel;
  • The spring starter, which allows you to slowly pull the cable, the engine does not scroll, but only a special spring is soared, at some point it overpoints the compression and sharply scrolls the knee shaft;
  • The decompression valve connects the cylinder to the atmosphere, while reducing the pressure in it, which allows you to start the engine without much effort, the valve closes after the start under the pressure of exhaust gases.

During the operation of the chainsaws can vibrate greatly, so it is equipped with an anti.vibration system of extinguishing vibrations. The saw handles are connected to the engine by means of a damper (rubber gasket or steel spring).

The sawing part of the chain consists of a cutting chain located along the edges of the tire, stars and chain wheel.

Likbez: CPG-cylinder-piston group.

Today we’ll talk about the CPG-cylinder-piston group. The piston and cylinder are the main components of the chainsaw engine, and the engine is its “heart”

Therefore, during the operation of a gasoline saw, it is necessary to pay attention to the prevention and control of the state of the cylinder-piston group constantly. In addition to the fact that its unsatisfactory condition affects the correct operation of the saw, its power, acceptance and other characteristics, so the cost of CPG can often reach half the cost of the entire chainsaw

So we will devote time to this important node, tell you what is part of the CPG, consider the malfunctions, some features of the CPG of the chainsaws

CPG device

So, what is part of the CPG (cylinder-piston group):

CPG is the main unit of the engine, the malfunctions of which inevitably lead to expensive repair. To maintain it in working condition, you only need to clearly follow the instructions and follow some general rules:

  • Use high.quality oils diluted in the exact proportion indicated by the manufacturer.
  • Avoid overheating of the engine.
  • Comply with work standards for the chainsaw class (household, semi.professional, professional).
  • Always use a correctly sharpened chain installed in the right direction.
  • Piston wear, cylinder
  • Wear of the rings
  • Mechanical damage (skip of rings, bearing)

All these and other not such common malfunctions ultimately lead to bully on the walls of the cylinder or piston, which in turn leads to the replacement of a completely cylinder-piston group.

How to diagnose as a result of which?

First of all, remove the muffler and in the formed window, inspect the CPG for bullying.

If the bullying is only from the muffler, then this is evidence that the chainsaw has overheated.

If the lines of the entire circle of the cylinder are uniform and they have great abrasion and dark color, then this is evidence of an incorrectly prepared fuel mixture.

If the bullys have the form of deep scratches located unevenly, then these are mechanical damage to the CPH that occurs if foreign bodies or chips of CPH parts enters the cylinder.

Blinds are located in the zone of the ring- poor quality of the mixture. It is also possible that the saw was drove “in the Soviet Union”.

thermal, piston, rings, motorcycles, causes

You can help in compiling the chainsaw rating by voting in the survey: “We make a rating of chainsaws”

Typical malfunctions of chainsaws and benzos (piston group): Causes and characteristic signs

The review provides examples of the most common breakdowns and malfunctions of the main parts of chainsaws (cylinders, pistons, etc.D.), with a photo of damage and analysis of the causes. The material was prepared by Stihl (Stihl) for service specialists and kindly provided to our editorial office.

Now you can find out by what signs the experts determine whether your case is a warranty, and why their reviews about the causes of breakdown are often so categorical.

Everything is simple. the vast majority of violations of the rules of the gas.pile and a benzo.leggos (did not add the oil to the mixture, did not clean the air filter, did not conduct timely maintenance, did not change the candle) lead to breakdowns with characteristic external signs. We publish a photo and an overview of typical malfunctions, the reasons for their appearance, methods of elimination and reviews.

Cylinder-piston group: Analysis of damage

Type: scratches throughout the work surface

  • fuel without motor oil
  • too low fraction of oil in the fuel mixture
  • aged or qualitatively unsuitable fuel

Reason: uncontrolled detonation due to application

Type: scratches throughout the work surface

Reason: the formation of too poor fuel mixture as a result

It has an increase in the speed of rotation and insufficient lubrication

Typical malfunctions of chainsaws and benzos (carburetor, air filter, crankshaft, clutch, etc.P.): See the reasons and characteristic signs at this link.

Type: scratches throughout the work surface

Reason: thermal overload due to insufficient cooling due to:

Causes overheating and, accordingly, a bully near the noise lord in front on the right

Type: scratches and the remains of the oil carbar on the work surface

Scored chainsaw cylinders and pistons, can they be reused?

Reason: Due to the use of unsuitable engine oil or tuning a carburetor on a too rich fuel mixture on the bottom of the piston, a strong oil carp is formed, which can be burned with an increase in temperature in the combustion chamber on the following conditions:

  • Carburetor configuration for the impaired mixture
  • Lining the mixture as a result of leakage (sucked by air)
  • The transition to another composition of the fuel mixture (for example, unhealthy gasoline or synthetic motor oil)

Reason: extraneous particles between the piston and the working surface of the cylinder (in the depicted case, the unskilled ring of the piston finger was released)

IMPORTANT! The locking ring is installed in the piston only with a cut up or down!

Reason: Particles of dirt and oil carpet in the exhaust channel hit between the piston skirt and the working surface of the cylinder

Reason: the use of unsuitable engine oil; The remnants of repayment stick between the piston rings and the piston and worsen the mobility of piston rings

Reason: oil for lubricating saw chains enters through leaks into the crankcase and combustion chamber and is deposited on the inside of the piston rings and on other details of the drive mechanism

Typical breakdowns of garden equipment. Warranty or not? We make “Parsing of flights” made at this link.

  • increased efforts on the piston ring that are transmitted to the piston jumper
  • Uncontrolled detonation due to the use of fuel with an octane number of 90 ROZ

Reason: penetration of large extraneous particles

Reason: the use of unsuitable engine oil

Consequence: damage to the lubricant leads to wear due to mechanical abrasion

Reason: abrasive dust causes increased wear of the piston skirt and piston rings

Elimination: control the condition of the air filter

How to repair a Stihl chainsaw 180

Question: What is the gap on the rings of the chainsaw of the Stihl MS 180?

Answer: on new ones-0.2-0.4 mm.

Question: How when buying a piston on a chain saw of the STIHL MS-180 to determine that it is original? I saw in a black store. And on the motorcycle stands gray, why so?

Answer: Black. a fake, the original STIHL spare parts should be spelled out, the sign “S” is printed.

Question: MS chainsaw 180, how and how to clean the carpet on the piston clean without removing the cylinder and harm to the engine? And the depth of the groove of the saw tire became 7mm, how to change it soon?

Answer: We do not recommend washing the carpet with any additives, only disassembly. If the depth of the groove is less than 5 mm, you need to change the tire.

Question: Today, the Stihl 180 chainsaw had to be disassembled, the first time in 4 years-stalling at idle after 10-20 minutes of operation. The carburetor dismantled to the screw-there everything was in oil-piles, washed everything, gathered, got it from the 5th.

Normal, but there are a lot of revolutions. the adjusting screw did not remember how he stood, screwed it as he could. Twist by ear? and what it regulates at all, idle or quality of the mixture?

Answer: This is a blast adjustment screw, turn it out when the engine is running until the chain stops rotating. In 180m, an unregulated carburetor, only idle speeds are regulated.

I usually screw this screw after the cross.cutting of the carburetor so that the gap between the screw head and the carburetor body is slightly more than 1 mm. And then I switch a little idle passage.

It is supposed to be on the tachometer. But you can do so. so that the normally stretched chain does not move on a warm engine.

Question: Tell me what exactly to clean in the carburetor. The mesh is clean, clean under the needle, I didn’t twist the adjustment screws, I’m afraid if I add to these symptoms I will add a carburetor to be cutting. you can definitely put a cross. can soak it in acetone?

Answer: by carburetor. Turn out everything that can be twisted. remove the lids, a locking needle, adjusting screws, a jacket. We do not pick out small caps inside, but on the contrary, check if we have reopened. And blow out of the thin nozzles under high pressure into all holes, starting with those where adjusting bolts were screwed. Then, when assembling the carburetor, screw the adjusting to 1 1/4 turnover and start adjustment by the tachometer.

Question: On the STIHL MS 180 chain saw, the ignition is installed according to the marks, taking into account the VMT or in another way?

thermal, piston, rings, motorcycles, causes

Answer: Magnetic steam should be opposite the ignition module at a certain distance.

Question: Is it possible to use mineral oil for 2-clock engines with air and water cooling of the equenol self-cooler to prepare the fuel mixture of the chainsaw of the Stihl MS 180

Answer: You can’t! You can use oil for 2-clock-cooled engines! We recommend only stihl oil.

Question: Is there an oil supply adjustment to the circuit?

Answer: No. Standard adjustment. With full gas, the oil is supplied to the chain, with idle, no.

Question: STIHL 180 chainsaw broke. The builders sawed her aerated concrete at a construction site. There is no result-piston, the saw does not start, the tire and chain in the garbage. I called the service center, they say the original piston 6300, and Chinese (Champion)-2000. Plus stuffing box and gaskets. Work for free (he was surprised).

Does it make sense to restore this saw if you put a Chinese piston there (the saw will rarely be used in the country) and change all the laying seals? I don’t have to buy a tire and a chain of new ones. On estimates, all repairs will cost about three and a half thousand. Is there any reason?

Gaps of piston rings.

Measurement of gaps of piston rings is often incorrectly understood and fucked up by part of the work to replace them. You can distinguish the minimum and maximum ring gap, which must be taken into account for the best result when installing a new set. The minimum ring gap should be taken into account without fail to prevent the ending of the ending, while the ring expands when the motor is supplied to the operating temperature. Piston rings scheme. For different thermal modes and types of engines, there are different recommendations of thermal gaps of rings: 1. Urban, utilitarian equipment not subjected to loads of high temperature conditions (such as in dragrasing or motors with ozot oxide), on average, gaps with a coefficient of 0 are installed.0045 x The diameter of the cylinder for one-ring pistons (two-stroke engines), as well as 0.003 x DC upper ring / 0.0038 x DC Lower piston ring with two rings (two-stroke engines). This includes mopeds, minimotias, scooters, highway motorcycles, cross-country motorcycles, ATVs and jet-cycles running on two-stroke engines. For four-stroke engines, the recommended gap of the first ring 0.004 x DC, second 0.005 x DC and oil.shock (both) at least 0.015 x DC. This also includes utilitarian motorcycles for crosses, ATVs and snowmobiles. 2. Racing, sports equipment, usually functioning in high heat load modes, requires minimum rings of rings a little more than utilitarian equipment: two tacts for one ring 0.005 x DC, for two 0.0045/0.0055 x DC Four Tacts. Upper Ring 0.005 x DC, second ring 0.0055 mm x DC and oils at least 0.015 x DC

For example: the diameter of the cylinder on the Moped Yamaha Jog 40 mm in the standard piston of this moped two rings, then the first ring is 400.003, which means the recommended gap 0.12 mm. The second ring is 400.0038, which means the recommended gap 0.15 mm.

Example: cylinder diameter on the Yamaha Tricker 74 mm motorcycle. Recommended gap of the upper ring 740.004, and the second ring 740.005. What does the gap 0 mean.29 mm of the first, 0.37 mm of the second and 1.11 mm butterfly. The declared value by the manufacturer: 0.19-0.31 minimum/maximum for the upper ring, 0.30-0.45 minimum/maximum for the second ring. DC. cylinder diameter.

Piston Failure Analysis-Overheating

Types of profile. In order to measure the gap of the rings, you will need a set of probes of a suitable size and the working cylinder on which these rings were or will be installed. Using not a new cylinder, you should make measurements in the lower part of the cylinder, since this part is not worn out, for which the rings are designed. The measurement of gaps of piston rings in the worn part of the cylinder will show an increase in the clearance in direct dependence of the degree of wear. The illustration below shows this. The effect of the cone of the worn cylinder on the gap of piston rings is depicted. If the cylinder is excessively worn, then it should be pulled out. The maximum gaps of piston rings are a lot of important component characterizing a decrease in compression, power loss and catastrophically weak oil control. This diagram shows the specifications for gaps of rings set forth in the SAE (World Complex Society) as standards for producers of piston rings. An important fact should be remembered that the manufacturer firmly adheres to these tolerances and the rings of the ring are checked by sensors with an accuracy of 0.0025 mm on DC. Any increase in the diameter of the cylinder is used in the case, everything that is more designed, as a result, gives about 0.076 mm increase in the clearance of rings for every 0.025 mm increase of DC. Manufacturers recommend a maximum of 0.076 mm wear for every inch DC, but not reach 0.30 mm in any case for successful and timely replacement of piston rings. If the cylinder is worn out in excess of this, the diameter should be pulled under the increased size of the rings of the corresponding size. Checking the clearance of rings can give information about the approximation of the cylinder wear as well as it will avoid errors when installing inappropriate rings. It is recommended to install rings in the correct order and position: do not place the clearances of the piston rod and the opening of the piston finger.

Do not try to close the expander of the oil tint rings, its endings should be freely adjacent. Unfortunately, different manufacturers have different recommendations for installing rings. How you will install rings, you decide.

Piston chainsaw replacement algorithm

If it is time to replace the CPG of the chainsaws, you need to know that for each specific model there is an individual algorithm of action. To facilitate the disassembly/assembly work, it is necessary to prepare a candle key, a large flat screwdriver, a hammer, a compressor for cleaning the parts of the unit, a set of rock and end keys. Regardless of the manufacturer and the design features of the model before removing the chainsaw cylinder, the following work must be done:

After removal from the base of the power unit, unscrew the pallet and take out the crankshaft with a piston from the cylinder. Using a locksmith tweezer or screwdriver, dismantle the piston fingers.

Sealant for fixing the shaft of the chainsaw

Before starting the assembly, compressed air, rags and other means to clean the parts and assemblies of the unit from dirt, remains of sawdust, dust. The first stage of replacing the piston chainsaw is to install the piston on the crankshaft. We fix it on the connecting rod with a steel finger that is included. In order to prevent the arbitrary loss of locking rings, it is recommended to install them with a cut down. Next, we mount the compression rings on the piston, but due to their fragility and brittleness to this operation, you need to approach as carefully as possible. To prevent the formation of scratches before installing the piston in the cylinder, grease the piston with oil. Before installing the crankcase (pallet), it will be necessary to degrease its mounting surface and apply a layer of heat.resistant sealant. The assembly of the chainsaw is carried out in the reverse algorithm described above.

Often the replacement of the piston of the chainsaw, crankshaft and compression rings solves problems with the idle stroke and with a problematic launch of the internal combustion engine.

thermal, piston, rings, motorcycles, causes

During the operation of the scooter, various breakdowns occur

At the same time, it does not matter who the manufacturer (Japan or China). The difference is that one transport earlier fails, and the other over time

Problems can occur with wiring, engine, chassis. But, as a rule, almost everyone faces the replacement of CPG. This reduction implies the term “cylinder-piston-group” or as the people “piston”. Looking ahead, it must be said that the replacement of the piston, piston and rings separately is not such a difficult task as it might seem at first glance. It is also worth knowing that the process of removing and replacing CPH is almost the same on all scooters. Therefore, the article will consider the main points. Looking back in advance, recall that the power of CPH can vary. It is recommended to install a piston of the same power similar to the standard CPG.

How to put a piston on a scooter correctly

The new piston is equipped with a finger, two locking rings and additional rings. If the scooter is 2 stroke, then the number of additional rings-2. In 4 strokes, 3 rings are almost always installed, one of which is oil. Consider the installation of a piston and rings on the example of a 2-stroke scooter. First, two compression rings are put on the piston, in special grooves. Next, the so-called “finger” is connected by the piston and the crankshaft, the fasteners are considered full after the installation of 2 stop rings on both sides of the finger. The rings should “sit” tightly in the intended holes. Remember: the arrow on the piston should look to the bottom, on the floor. The described “processes” are not complicated if you figure it out. It is best to watch a training video or familiarize yourself with the instructions for the maintenance of a scooter. Then probably there will be no questions like “How to put rings on a piston of a scooter”.

Benzo tool. Likbez

Documents corresponding to your request: 9

All my attempts to find out what kind of model it is and in what years it was produced, turned out to be in vain (I will be very grateful if you help me with something in this matter). Nevertheless, I can approximately assume that it is somewhere in the 60-70s of the last century. Bosch uses a chainsaw.

Number 21554 knocked out on a crankcase. What number it is, for me a riddle.

On the left side of the saw there is a sign with the inscription.

What information is indicated for me. dark forest :-))).

I partially dismantled the chainsaw (to clean and evaluate the state of parts). I also replaced the tip of the spark plug (he cracked everything) and installed the ignition switch (it was absent at the time of purchase of the saw). This information, as you know, is not original :-))). And one more minus. The absence of a lid of the oil depot. (In the photo everything was marked with arrows).

There is a chain on the saw. Takasago (I have never heard about it, but this is evidenced by the inscription on the cutting tooth).

Dolmar chainsaw. About three or four months ago I had this copy in my hands Dolmar chainsaw.

Dismantling. Assembly of the chainsaw of the Stihl MS180. Satisfaction of the application: 21.43% Fragments of the text of the message. Dismantling. Assembly of the chainsaw of the Stihl MS180. STIHL MS180 dismantling chainsaws. STIHL MS180 assembly chainsaw.

Replacing the piston group with a chainsaw or trimmer

Repair at this level should always be balanced. In such small, high.speed engines, replacing one burned or stuck piston does not give a long result, and, if necessary, it is necessary to replace the entire piston group. Therefore, you need to decide whether to continue to use this saw or buy a new saw.

If this is a professional model, then such a repair should be carried out, but if it is an old household model, such as Husqvarna 40, and it worked for more than ten or twelve years, it is unprofitable to repair it. Since its repair will cost as much as buying a new saw, albeit not Husqvarna, but on Partner P350XT Chrome, the cost is 165, of course, quite sufficient. In addition, Husqvarna sells such saws, as Partner is her subsidiary.

But if you still decide to repair a chainsaw or a trimmer for grass, then you need original spare parts that are expensive. If the engine works fine, the first repair may not occur soon, and only the piston rings or rings, depending on the model. But if the saw is stuck, you need to change the entire piston group. cylinder, piston and rings.

It should be noted that the chainsaws of Husqvarna 136/141 have a service life of approximately 500-600 hours, Husqvarna 340/350. 1000-1200 hours, professional chainsaws of at least 2000-2500 hours, subject to strict compliance with the instruction manual. In fact, these figures cannot be relyed, since a real resource can vary significantly both up and down. But we can roughly say that semi-professional saws work 3-4 times longer than amateur, and professional. up to 10 or more times.

When you need a piston replacement

The reasons why the piston must be replaced, as well as completely piston, there may be quite a lot, but all of them can be divided into natural and emerging as a result of improper operation. Natural, this wear is formed due to the prolonged operation of the Stihl 180 chainsaw. There are much more artificial ones, for example:

overheating of the engine and the appearance of thermal bullying;

  • entering the cylinder of a foreign body and the appearance of mechanical bullying;
  • the bummer of the piston ring as a result of exceeding the maximum engine speed;
  • the wreck of the piston skirt due to excess revolutions;
  • the use of poor.quality fuel, as a result of which the piston group of the chainsaws wears out from the side of the intake channel in the cylinder;
  • Operation of a stihl chainsaw with contaminated fuel filter, as a result of which the percentage of oil in the fuel mixture is reduced;

Diagnosis of CPG is necessary if the STIHL MS 180 has sharply lost power or does not start, while the tool starter does not turn. If the starter is turning, but the saw does not start, while there is a spark and fuel enters the cylinder properly, it is necessary to measure the compression in the engine.

9.5. 11 atm. It is considered a normal indicator in which the StiHL chainsaw is regularly launched and gives out maximum power, if the compression is lower, there is a possibility that there are bunches on the cylinder.piston group, or its wear is large enough. In any case, with reduced compression, for further diagnosis, it is necessary to completely disassemble the saw.

Determine the presence of bully on the piston, as well as the wreck of the piston ring, if you remove the muffler and conduct a visual inspection of the visible part of the piston, while the rings for elasticity can be checked by pressing them with a small screwdriver. A small walk will be observed on the working rings, there will be no defective or clamped piston ring.

Fuel system

So that as the fuel consistency is spent, the fuel tank was filled with air and negative pressure was not created in it, which would not allow the combustible to enter the carburetor, and with all this, so that a fuel does not flow out of the opening for air, in the lid that closes the pouring hole, Brown of a sapun. And by the way, if the saapun clogs with a dirty rod, then the chainsaw will staller.

From the tank, fuel sways through the hose freely dangling in the tank. Husqvarna; Who knows where the gas tank saepun is and how its saepun is in the upper part. Thanks to this, regardless of the position of the chainsaw, the hose is always immersed in fuel. The fuel filter is attached to the inlet end of the hose. A combustible carburetor snut.fuel.

To facilitate launch, part of the chainsaws are equipped with a manual pumping pump. a primer. When starting a chainsaw with a primer, the carburetor is filled with fuel in advance (an excess of fuel flows back into the tank). Thanks to this, the engine triggers, t.to. The stage of filling the carburetor is already passed by fuel, which is made without a primer by a carburetor pump due to the starter.

Piston chainsaw replacement algorithm

If it is time to replace the CPG of the chainsaws, you need to know that for each specific model there is an individual algorithm of action. To facilitate the disassembly/assembly work, it is necessary to prepare a candle key, a large flat screwdriver, a hammer, a compressor for cleaning the parts of the unit, a set of rock and end keys. Regardless of the manufacturer and the design features of the model before removing the chainsaw cylinder, the following work must be done:

  • Dismantling the upper protective cover;
  • Spinning candle twisting;
  • Removing the side cover;
  • With the help of a large flat screwdriver, stoppers from shock absorbers are removed;
  • In the candle channel, place the cranberry lamp and unscrew the clutch and nut of the flywheel;
  • Dismantling the leading star of the chain;
  • We remove the carburetor with an air filter;
  • Remove the ignition module and exhaust system.

After removal from the base of the power unit, unscrew the pallet and take out the crankshaft with a piston from the cylinder. Using a locksmith tweezer or screwdriver, dismantle the piston fingers.

Before dismantling the Piston, it is necessary to remember its location in the cylinder in order not to spend time subsequently on re.disassembling and assembly of a power unit.

Sealant for fixing the shaft of the chainsaw

Before starting the assembly, compressed air, rags and other means to clean the parts and assemblies of the unit from dirt, remains of sawdust, dust. The first stage of replacing the piston chainsaw is to install the piston on the crankshaft. We fix it on the connecting rod with a steel finger that is included. In order to prevent the arbitrary loss of locking rings, it is recommended to install them with a cut down. Next, we mount the compression rings on the piston, but due to their fragility and brittleness to this operation, you need to approach as carefully as possible. To prevent the formation of scratches before installing the piston in the cylinder, grease the piston with oil. Before installing the crankcase (pallet), it will be necessary to degrease its mounting surface and apply a layer of heat.resistant sealant. The assembly of the chainsaw is carried out in the reverse algorithm described above.

Often the replacement of the piston of the chainsaw, crankshaft and compression rings solves problems with the idle stroke and with a problematic launch of the internal combustion engine.

It seems to have found a piston, maybe not everything is so scary))

Please tell me, replaced the piston and the sleeve, started it, worked for about 5 minutes, I couldn’t start it again, the autopsy showed the grooves on the sleeve and the piston. the rolling pin broke off the edge of the intake window and struck the sleeve. Reason 2 replacement of the piston-the same, the lack of compression, the reason is scratches from some kind of metal chip. They are, before assembling a file, you need to go through? What kind of trouble is?

I can assume this. one. The quality of the spare parts is no 2. Lack of oil in gasoline 3. When heated, the piston expanded and caught the wedge, perhaps not the correct size or overheating.

I think to change the piston 3 times, or is it easier to buy a new engine. Thanks.

When installing a little oil, I greased all gasoline diluted with oil more before installation, I would look like the piston in the cylinder itself on the cold air filter and a good.legged runner

Installation of piston rings on one.time tractor

The piston rings form a seal between the cylinder wall and the piston. Must provide good seal along the entire cylinder plane in a wide temperature range. Three rings are more often used in four strokes, of which there are two compression and lower oilfold.

  • Compression rings provide a reliable seal between the cylinder and the piston for sealing the combustion chamber.
  • Demolition of heat from the piston to the walls of the cylinder.
  • Oil shooting rings remove excess oil from the walls of the cylinder preventing it from getting into the combustion chamber. However, they are not completely removed, but regulated, leaving the required amount of oil for compression rings.

The first compression ring

Intended exclusively to prevent the breakthrough of expanding gases in the combustion chamber. During the “working move” cycle, the increasing pressure in the combustion chamber presses the first compression ring to the bottom of the piston groove and presses more to the cylinder walls, thereby ensuring sufficient insulation of the combustion chamber. The pressure in the groove of the ring remains on subsequent strokes without having time to decrease. The gap between the ring and the groove is 0.04-0.08 mm

Protects the second ring from high combustion temperature and reduces the load. It has the highest heat sink from the piston to the cylinder, approximately 50-60% of the drained heat from the piston to the cylinder falls on compression rings. Some of the gases break through, the second ring begins to fulfill its functions, more on that later.

The first compression ring is made of high.grade cast iron or steel that can withstand high temperatures and the load while having a not large coefficient of thermal expansion. During the engine operation, the ring temperature reaches 180-210 ° C, at the upper dead point where there is practically no lubricant due to friction, even greater temperature is achieved. There is often a special coating to reduce friction on the outer working surface of the ring. It can be a plasma surfacing of molybdenum, cermet, ceramics. There is more often a chrome coating with a gray matte color (applied by a galvanic method) and a kind of porous structure that allows you to delay oil to reduce friction. The remaining surfaces are black as a result of phosphate. The coating provides antifriction and anti.corrosion properties.

Compression rings are not entirely round, but have a complex shape of an arc in a free state and a fairly large end clearance. When the ring takes its place in the piston and will be inserted into the cylinder, it will provide uniform clamping force anywhere in the circle.

The second compression ring

It works in more favorable conditions and performs the function of additional seal in the same way due to the special form helps the oilfield to remove excess oil, leaving only an oil film on the surface of the cylinder. The average temperature of the ring is 150. 170 ° C in operation mode. The gap between the ring and the groove of the piston is slightly lower than that of the first.03-0.06 mm. Made of cast iron and very fragile. A variety of rings forms determines the performance of certain functions. Such as the distribution of the load in the groove, reducing the friction of the piston skirt by the method of oil.planning, removal of excess oil.

The chamfer on the inside of the ring determines which way the ring will bend. If the chamfer is from below, then after heating the ring will turn out the outer surface down, as shown in the picture. And accordingly, if the chamfer is from above, then the working surface of the ring will turn upward.

Oil scraper ring

Under the compression rings, there is an oil scrap ring that performs the function of removing excess oil from the walls of the cylinder.

A large amount of oil penetrating through compression rings into the combustion chamber does not affect the engine work well. In the process of working, the burning oil is laid on the walls of the valves, the combustion chamber, candles, the bottom of the piston. A large carbon fiber is greatly heated, the likelihood of detonation is increasing. The exhaust valves are subjected to increased temperature load.

A thin layer of oil film left by oil.beetle rings reduces the strength of the friction of compression rings, increasing their durability. Unlike compression, oil.removing are not pressed by the working pressure of the gas to the plane of the groove in the piston and the walls of the cylinder, therefore they have special axial and radial expanders.

Two types of rings can be distinguished by design: they can have different expanders and others.

When the piston moves down, the oil scrap rings are scraped away from the walls of the excess oil cylinder directing them along the drainage holes in the piston back to the crankcase. Oil wedge in front of the ring helps effectively lubricate the sliding skirt of the piston. The walls of the cylinder have roughness, the so.called Hon, which allows you to delay the thinnest layer of oil, for compression rings.

Set rings consisting of two thin steel plates (often having various coatings to reduce thorns) and a tangential expander, which simultaneously performing axial and radial expansion are more widespread. Used in modern engines.

Correct installation of piston rings

Sooner or later, your motor will be worn out and will require either a change of piston rings or a piston in general.

It seems to change the piston rings is an ordinary task available to everyone who is more or less familiar with the device and the principle of operation of a primitive four-stroke motor. But, unfortunately, people are afraid to spend 15 minutes of their incredibly precious time reading literature and stuff everything into the motor according to the principle (as well as stood. will probably work). Well, the flag is in your hands and the speedy appeal to the service.

Well, for those who do not care how their motor will work after bulkhead, you should read this article.

So, take the piston and see 3 grooves for the installation of piston rings. There are no restrictive stoppers on 4-stroke engines, as on 2-stroke engines, for example.

There are two types of piston rings on 4-stroke engines. The first two, which are installed in the top two grooves, are compression. Based on the name, it is clear that they are responsible for the presence of compression in your motor and properly to keep the gases that form at the time of the outbreak due to combustion of fuel in the combustion chamber.

The following three rings are oil.scrubbing. Here, too, their purpose is also clear. They are responsible for relieving oil, which covers the cylinder walls at the moment when the piston returns down. If these rings are passed, then the oil will remain on the walls of the cylinder, and this is fraught with the fact that the engine will begin to burn the oil, and, of course, smoke will appear.

How to install primary? Yes, in principle, as they stood from the factory, in the same order, but in order to avoid mistakes, we show again.

Initially, we put the main oil scrap ring: that which has a wave.like structure. There is nowhere easier to install it, since it is the most elastic of all.

Then put the upper and lower thin oil scrap rings. They are a little harder, but there should be no problems with their installation either.

Now we put piston compression rings: those that are thicker and “hard”. Initially, install the lower, then the upper. Put them a little more difficult, since they are less elastic and more solid. You are unlikely to break them, but with completely crooked hands to bend them easier.

The fact is that the rings still need to be properly placed on the piston so that the locks of the rings (the location of the drink) do not fall on top of each other. Simply put, it is necessary that the lower ring is not located right above the cut of the upper ring.

The castle of the lower ring is placed in the middle above the valve cavity, for example, inlet (you can also graduate, there is no difference here).

The locking of the upper ring is placed strictly on the opposite side of the lower ring. Accordingly, if the lock of the lower ring above the cavity under the inlet valve, then the upper castle above the cavity under the outlet valve.

Now go to the oilfly rings. These rings must be placed in the same way so that not a single castle coincides. Therefore, the upper ring is located above the hole under the piston finger, on the right side.

The second (that which is lower) is placed on the opposite side, also approximately in the middle of the hole under the piston finger.

The last wave.shaped oil.welded ring is placed in any of the four resulting sections between the opening under the finger and the cavity under the valve.

And now to your question: what kind of nonsense is the author rubs us here? And why so painstakingly set the position of all 5 rings?

Explain. We did all this so that it did not happen that when one castle was located above the other, gases do not pass through these locks (in the case of piston rings) and did not remain on the walls of the oil (in the case of oil.cut rings).

If we take into account the piston rings, then this is the loss of compression and the passage of hot working gases to oil.beet rings, which are not designed for such sudden high operating temperatures. As a result, the rings after a certain time can burn out.

If we turn to the oilfield rings and the coincidence of the locks on them, then we will not be completely removed by the oil: it will reach the piston rings, which will lead to the hair strokes of the rings, and as the result they will varify, and then burn out.

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