How to check your chainsaw for air intake
Why a chainsaw malfunctions when idling
The engine on a chainsaw or brush cutter consumes a certain amount of air during operation, its excessive suction through loose connections, carburetor or faulty seals, dangerous and here’s why.Good afternoon dear subscribers and guests of the channel.
The engine of a chainsaw or brushcutter is two-stroke, runs on a petrol-oil mixture, due to which the bearings of the crankshaft, connecting rod, cylinder walls, piston and compression rings are lubricated.
In the crankcase of a chainsaw there is periodically a vacuum and overpressure, due to this phenomenon works gasoline pump in the carburetor, which is connected to the crankcase by special channels or a hose.
Thus it turns out that extraneous air intake can affect the operation of the fuel pump and the amount of air in the fuel-air mixture, respectively, the quality of lubrication.
Let’s start with the worst. When the brake pedal is depressed and the brake pedal is depressed, the brake pedal is released. Due to this deteriorates the quality of lubrication of internal engine parts. It also causes increase of idling and maximum engine rpm.
As a result of poor lubrication and high revs engine overheats, leading to disastrous consequences, up to piston seizure or destruction of crankshaft and connecting rod bearings.
If air suction occurs in the carburetor or gasoline pump system, the latter will not fill completely and therefore supply enough fuel to ensure normal engine operation. It will reduce power, the saw will work at idle, but you won’t be able to make good cuts anymore.
Again, it depends on how much suction is observed. In some situations the saw stops starting up completely or starts, but stops immediately when you press the gas.
Why chainsaw does not pick up speed under load
Owners of chainsaws sometimes have to deal with the fact that the saw, for no apparent reason, stops working normally. To understand why the chainsaw is deaf in different modes of operation, as well as to describe how you can diagnose a malfunction, we will try in our article.
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Why the chainsaw stops when it heats up
Situations where the chainsaw starts
in the cold, and in the process of heating can stall, is familiar to many who are associated with them. The main causes of this behavior are.
The ignition module (coil) is defective. Determine the problem by checking the spark first on a cold engine and then on a hot engine. If there is no spark on a hot engine, then try to solve the problem by replacing the ignition coil.
Check the ignition coil with a multimeter or by replacing it with a well known. Multimeter of the primary and secondary winding is tested in resistance measuring mode. The resistance index of the primary winding, the working coil, is 1 kOhm. Secondary 4 kOhm.
Why a chainsaw stands under load
In some cases, the chainsaw under load can’t work properly and just lies down. A common cause of this behavior is improper carburetor adjustment or air intake through the crankshaft oil seals or carburetor gaskets. It can also happen because of the carburetor leakage.
To diagnose the cause and fix the fact that the chainsaw starts and stops under load, this is best done at a service center, as a special tool is required to check the carburetor and engine crankcase for leaks.
A saw that cannot run under load is also hesitant to hold up. They will “float.”. Diagnosis begins with checking the crankcase and carburetor leaks. If air leaks are found through the crankshaft oil seals, they must be replaced. If air intake is found in the carburetor, a gasket repair kit can fix the cause.
Only after the above steps have failed and the carburetor engine crankcase is sealed, can you begin to tune the carburetor.
The reason for this algorithm is that if the air intake from the crankcase is not eliminated, but the carburetor is simply adjusted for normal engine operation, the fuel mixture will contain more fuel than required for a sealed crankcase, which will significantly increase its consumption at a turn. Also, it is likely that the engine will have carbon deposits, which will also negatively affect the further operation of the chainsaw.
In some chainsaw models, to ensure the operation of the fuel pump, special hoses are installed, which transmit the air pulse from the engine crankcase to the carburetor fuel pump. If this hose is removed, the saw will run unevenly at idle and will not run at all under load.
The saw does not develop speed, does not develop power.
Why this problem occurs? saw
Worked fine, but suddenly the power was lost and wouldn’t advance.
Chainsaws stop when you press the gas. we are tuning the carburetor. Chainsaws stopping on throttle
The video discusses a fairly common chainsaw error
и 100%.The carburetor tuning method. How to do it.
Owners of Husqvarna 137 and Husqvarna 142 residential chain saws should check the pulse hose first for any engine deviation, as this is considered the most common cause of failure on these chainsaws.
The engine stalls
Engine is running but chainsaw stalls when idling or under load. In this case, it is often necessary to carry out the same actions as described above.
How to adjust the chainsaw depends on exactly when the problems begin:
Stops right after starting:
- The fuel mixture is not mixed properly, there is too much oil in it, the gasoline octane rating is lower than it should be, and the chain saw only runs on a blow-off or immediately stops.
- Cinder on the spark plug or improper gap between the plug and the wire.
Stops and does not idle:
- The muffler is clogged. You need to clean the carbon deposits.
- The carburetor settings are jammed. The idle speed needs to be adjusted on the chain saw. You can adjust the throttle trigger with the L and H adjustment screws. How to adjust the idle speed, see the article about adjusting the carburetor.
Stops at maximum engine rpm and runs on suction valve only
- Clogged air or fuel filter. Seals need to be cleaned and checked.
- The breather plug is clogged, which prevents fuel flow and gasoline pumping on the chain saw. Take a needle and clean the breather gently.
- Gasoline pump malfunction. Remove pump and check if it is leaking gasoline. If leaking: Replace gasket or pump.
Chainsaw won’t cut under load and shuts down
- Clogged air filter. Must remove filter, flush or even rinse well, dry out and install again.
- Incorrect petrol-oil mixture proportion. Drain the fuel and mix the oil and gasoline in the correct proportions.
If unusual noise like gunshots occurs, there is a problem with the muffler or carburetor. How to make your chain saw run quietly? It depends on which particular part of the carburetor is malfunctioning.
The chainsaw shoots into the carburetor :
- Late ignition. the air-fuel mixture has too little time to burn through the cylinder, so you get a sound like a small explosion.
- Depleted fuel/air mixture. There is too little gasoline in the mixture. you need to adjust the chainsaw, or rather the jets, to increase the fuel supply. Why the chainsaw fires on its own. the same reason.
The chainsaw shoots into the muffler :
- Enriched fuel-air mixture. Reasons why chain saw fires? There is too much gasoline in the mixture, but not enough air, so the mixture doesn’t combust completely in the chamber and partially burns out in the muffler. The soot on the exhaust is a clear sign of this. Need to clean air filter or adjust carburetor.
Why the chainsaw engine won’t start?
If your new chainsaw engine won’t start, the following could be the cause:
- The tool is not properly prepared for starting.
- The fuel mixture is of poor quality, “old” or improperly mixed fuel.
- The sequence of actions during start-up is broken.
When the engine of a used chainsaw fails to start (usually after long downtime, unqualified repair, or as a result of natural wear of parts), in addition to the reasons listed for the new tool, the problem may be the following:
Clogged air filter
The fine dust that forms when cutting wood is the main cause of filter blockage. Sawing raw wood is especially blocked. Of all the reasons for a chainsaw stalling, this is the most common. Some models are an exception. STIHL chain saws stop for various reasons, but not for a clogged air filter. Because its carburetor has a compensator that takes in air if the filter fails. Particles of wood dust get under the housing and are sucked in by the filter mounted on the carburetor. A clogged wire mesh creates a resistance to air, and less air gets into the carburetor. To clean the air filter, you must remove the closing cap and separate it from the carburetor.
Before removing it, brush off the sawdust or blow it out with air. Then take out the filter so that the debris does not get into the carburetor. Cover the carburettor with a rag for the time of cleaning. Then the filter should be blown internally with compressed air and then installed.
Why the chain saw doesn’t rev up and shuts down
If the chainsaw a minute after starting is unable to pick up speed or shuts down when you pull the throttle trigger, most likely the carburetor or the engine crankcase is leaking. As in the previous case, the problem can be solved by checking for leaks and adjusting the carburetor.
If the chainsaw fails to pick up speed and shuts down after it has been running normally for about 5 minutes, the cause may be a defective fuel tank breather. The vacuum created in the fuel tank during work of the tool does not allow the engine to receive the necessary amount of fuel for normal operation and for this reason it will be unable to gain revolutions or will stall. If you stop the tool, open and close the fuel cap and start the chain saw again, the tool will run fine for about five minutes, after which it will either stop revving or choke.
The cause of the chainsaw not picking up speed may be excessive soot in the muffler, which prevents the exhaust gases from coming out, thus reducing engine power and speed.
If you want to check the tightness of the crankcase, but do not have a special tool, you can use the following test procedure.
Algorithm of checking the crankcase for leaks
- Remove the side cover and guide bar from the chainsaw.
- Unscrew the spark plug and through the spark plug hole put a string with knots in the cylinder, thereby stopping the movement of the piston and the crankshaft.
- You can use an old starter cord as a cord with knots, tying knots on it at 3-5 cm intervals.
- Unscrew the chain saw’s drive sprocket.
- Remove the oil pump cover and the pump.
- Remove the starter motor from the chainsaw.
- Unscrew and remove the flywheel.
- Remove the carburetor.
- With a syringe, through a hole under the carburetor in the cylinder, pour petrol into the crankcase, while watching the crankshaft oil seals. If gasoline will leak through them, it means that the oil seals are out of order and need to be replaced with new ones.
- It is better to leave the installation of oil seals to professionals.
An indirect sign of a leaking crankcase is oil leaking from the oil seals.
Why does the chain saw choke on heat?
It often happens that the chainsaw starts when it is cold but stops when it is hot. This behavior can be caused by the following:
- The carburetor is not properly set. You can identify the problem by the way the machine is started in the cold. If it is made without closing the air damper, and the engine is started without pre-flash, it means that after heating the engine, the fuel floods the spark plug. The solution to this problem is to adjust the carburetor. Read more about carburetor adjustment
- Coil (ignition module) malfunction. You can check for this problem by running a spark plug test first when the engine is cold and then when it is hot. If there is no spark on a hot motor, you need to replace the ignition coil.
- Faulty spark plug. In this situation, as with the ignition module failure, the spark disappears when the engine heats up. The spark plug should be replaced with a new one, and if that does not solve the problem, the ignition module and the distance between it and the flywheel should be checked.
Problems “On Hot
If you notice that your chain saw has no problem starting without warming up, but stops after warming up. And it will not start until it cools down, then here, there may be several problems.
First, there may be a leak in the hose, packing or gasket somewhere. Second, inspect the muffler for fouling. The third reason is the cylinder piston group (BCG), whether there are any scuffs or irregularities.
Sometimes you need to adjust the carburetor. Another important cause of malfunction is the ignition coil. In cases where it fails, the spark is lost or becomes very weak, which is not enough to ignite the fuel mixture.
There are cases when the master is trying the engine hard, then on the cold, then on the hot, thereby pumping fuel. Here you need to pull yourself together, put the choke on “hot start” and gradually start the tool. In this case, knock down to almost idle rpm and 40-45 seconds it warms up.
Problems “On hot
If you notice that the chainsaw has no problem starting without warming up, and after warming up it stops. And it will not start until it cools down, then here, there may be several problems.
First, there may be a hose, packing or gasket leak somewhere. Secondly, inspect the muffler for fouling. The third reason is in the cylinder-piston group (CPG), there are no scuffs or irregularities there.
Sometimes you need to adjust the carburetor. Another important cause of malfunction, is the ignition coil. In the case when it fails the spark is lost or becomes very weak, which is not enough to ignite the fuel mixture.
There are cases, when the master is trying hard to engine, then on cold, then on hot, thereby pumping fuel. Here you need to take control of yourself, put the choke on “hot start” and gradually start the tool. In this case, knock down the revolutions to practically idle and warm it up for 40-45 seconds.
Causes that cause the chainsaw to stall under load
In this article of the construction site will be considered the main reasons why the chainsaw can not start or stop when loaded.
The most common of all, are the following causes:
What’s causing the chain saw’s power to drop?
The same goes for the air filter, it should be cleaned immediately if this kind of problem occurs. Now for the spark plug, if it is very dirty it also needs to be cleaned and adjusted if necessary. It is the wrong gap between the electrode of the spark plug on the chainsaw that can cause it to begin to stall, and in general, work extremely unstable.
The compression in the engine can reach 28-36 atmospheres. It means that at the end of the compression cycle the temperature will rise. If there are some faults with the turbine, then the oil will inevitably leak, and it tends to burn. The diesel fuel mixes with the oil. And already the engine is in full swing. it revs up by itself, makes noise and smokes. Oil pressure rises and then the lubricant is also sent to the cylinders. So the engine runs like that until it’s smoky. The high load can also cause a runaway.
Malfunction associated with oil in the exhaust manifold can be quite dangerous. It causes fires in the exhaust manifold. Also due to overheating, the engine jams. And as it has already been noted, the engine is destroyed because of the increased mechanical loads. So, why the engine goes to pieces, it is clear to us. The causes may be different, and to eliminate this phenomenon it is important to know what exactly triggered such motor behavior. If there is black thick smoke coming out of the exhaust pipe, and the speed rises quickly, most likely the problem is in the turbine.
What to do if the chainsaw stops?
Builders, installers, rescuers and cottagers #8211 they all pick up a chainsaw sooner or later, while performing their tasks. And the final result of their activities largely depends on how reliably this tool will work.
A chainsaw is used to cut wood.
It is worth noting that the chainsaw belongs to relatively uncomplicated devices. Nevertheless, it, like other mechanisms, fails from time to time.When a chainsaw stops working at idle (this is one of the most common faults), the biggest challenge #8211 is to determine the causes of such behavior.If the source of the “illness” is correctly identified, it will not be too difficult to return the machine to operation.
The first thing you must do is to find out what malfunctions your chainsaw has and what causes the engine to idle.
Components of a chainsaw fuel system
After getting to know the system and its construction superficially, let us take a closer look at each component for a more nuanced understanding. How different are the forms of the same parts in different chainsaw models, and how they can be installed. Explains the detailed features of the fuel system components, with clear photos, below.
In most models, the fuel storage tanks are built into the body and are a monolithic structure with a handle. Replacement of such a tank in case of burnout or mechanical damage, requires complete reconnection of gas levers and air damper (in addition to hoses). You may encounter systems that at first sight look separable (STIHL MS 440 for example), but even there the tank is integrally connected to the body and is not sold separately from the handle.
In addition to the chainsaw body, the fuel tank may be located in the crankcase (for example, Partner 351). In this case, the process of replacement in case of damage, is longer and more laborious, because it requires disconnecting almost all parts of the tool, including the engine. Fortunately these designs are not always monolithic and it is possible to find machines where the fuel tank and oil tank can be removed (STIHL MS 180), making repair work much easier.
Rather important and popular consumable, providing protection of carburetor and engine from contamination and premature failure. According to the type of design, there are 2 varieties of filters: in plastic housing and in metal housing. As a cleaning material can be used nylon (in plastic Chinese elements), felt (in all types of cases), cortex (in plastic) and polymer foam (in metal).
Regardless of the material of manufacture, every chainsaw fuel filter has a weighted filter that guides it to the lowest part of the tank when the saw is tilted.
Polymer foam and cortex provide the highest degree of protection against small particles. Felt is no less reliable, but clogs up rather quickly. Nylon nets are categorically unsuitable for such purposes, therefore, having bought a Chinese saw with such equipment it is better to change it for one of abovementioned at once. The replacement must have an identical socket diameter, which can be 3.5, 4.5 и 5.5 mm.
The most flexible part of the system, performing the transfer of fuel from the tank to the carburetor and primer (if available). in budget versions, made of silicone and completed with a gasket in the form of a bushing or without it at all and just fits tightly into the hole in the tank. Better quality hoses are made of dense gasoline-resistant rubber, and as a sealing contact, have special tabs, pressed to the tank from both sides.
Of course, in terms of durability, a special rubber fuel hose for a chainsaw will last longer before it starts to dry out and crack.
In a classic chainsaw system, there is only one fuel line connected to the carburetor inlet connection. In the presence of a hand pump (primer), the number of hoses increases to 3, where the first performs the main role, the second connects the carburetor and primer, and the third removes excess fuel from the primer back into the tank.
Chain saw check valve (breather)
Devices of small size, but of great importance for the entire fuel system. Located at the top of the tank and ensures the normalization of pressure, when the volume of fuel decreases. Of the most common, we can distinguish 2 types of breathers: simple (cone-shaped) and collapsible (float). Both variants are widely used, both in amateur and professional tools.
In addition to the standard valves, some models of saws are equipped with completely unique elements. For example, to replace the breather on the Makita EA3203S and STIHL MS 660 you will need to pick up a completely identical part.
If the valve bypass channel is clogged, air will stop flowing into the tank, which is necessary to normalize the pressure against the fuel being pumped out. Because the tank is hermetically sealed, a vacuum will begin to form in the tank. With each new “eaten” batch of fuel, the carburetor will have more and more difficulty pumping. At this rate, operation continues for a few tens of seconds until the diaphragm pump stops. If the tool stalls due to a clogged breather, then when you unscrew the gas tank plug, air will be sucked in sharply, normalizing the pressure.
The main distributor and the intermediate link between the gas tank and the combustion chamber. Includes a diaphragm-type pump that operates by air supplied from the engine crankcase through an impulse channel. The second connector is connected to the fuel hose, which transmits the mixture from the tank. If the chainsaw is equipped with a primer, a modified carburetor model is installed in it, with an additional (third) connector.
How to Check the Fuel Filter on a Chainsaw
A reduction in the capacity of the main fuel line, causes a highly undesirable phenomenon manifested by a drop in power or a complete stoppage of the engine when the revolutions are increased. These problems can be a clear signal that the fuel filter is clogged. The more pronounced these problems, the more clogged the channel.
It is not always possible to determine the need for replacement by visual inspection. The filter may look clean, but the inside is caked with fine particles and sediment. To identify the reason for failure for sure, you can experiment by removing the filter and running the tool without it. If it stops working normally, a new element should be installed.
In companies that use the chain saw regularly, 5 days a week, the filter should be changed about every 3 months. If in 1 day the tool burns ≈ 5 liters of fuel, then in 60 days we get 300. For household saws, this figure can be divided by 2 because they are equipped with less reliable filters. Bottom line, in home/hobby use, replace every 150 liters or once a year.