How to repair a chainsaw with your own hands

Types of faults and repair chain saw “STIHL 180

A chainsaw is a common type of chain saw. Such a device is widely used in construction work, cutting firewood and other various operations with wood. But no matter how good the tool may be, malfunctions can occur in its operation. Repair of chain saw “STIHL 180” more profitable to hold on their own, as it will save not only money, but also help to understand her device.

Before identifying malfunctions and repairing the STIHL 180 chain saw, it is important that you understand how it works and which components it consists of. The chainsaw is necessarily composed of its main element. the two-stroke engine. That is responsible for reliability and performance. The engine is involved in starting the chain drive and maintaining its movement under the action of the centrifugal clutch. In addition to the electric motor, the chainsaw includes:

  • starter;
  • flywheel, which is also a cooling unit;
  • ignition unit;
  • clutch and brake mechanism;
  • STIHL compensator carburetor;
  • air filter;
  • fuel and oil tank;
  • muffler;
  • antivibration system.

Fuel goes from the tank to the carburetor, where it is mixed with air from the cleaning unit. From the carburettor, the mixture of air and fuel enters the engine. The carburetor has a carburetor screw that controls the idle speed. All adjustments are made at the factory to ensure an optimal fuel/air mixture.

The mixture is ignited in the engine cylinder, and the starter motor is used to start the engine. The piston acts on the shaft, which is part of the crank mechanism, to start its movement. There is a sprocket on the shaft onto which the chain links are put.

The chainsaw uses a single-cylinder motor. A clutch is used as a safety mechanism that enables the motor to idle in the event of jamming. At the initial revolutions, special pads, located in the radial direction, are pressed by springs to the middle of the shaft, thus preventing it from rotating. At high RPM, centrifugal force increases, causing compression of springs. The lugs are pushed off the center of the shaft, the sprocket rotates and the chain starts.

The electrical circuitry of the device is involved in the ignition system. The use of a flywheel with magnets generates an electromotive force (EMF) as it rotates, which induces a current in the electronics unit. The unit sends a signal to the spark plug, causing a spark to be produced on the plug pins. This spark ignites the mixture coming from the carburetor. After a successful start-up, the chain saw is cycled through all processes.

The chain of the device is made of prongs and connectors. To protect the user from backfire, the device is equipped with a brake system. The oil is fed automatically by a pump.

How a chainsaw carburetor works?

The main purpose of a carburetor is to mix fuel with air in the necessary proportions. If the latter is disturbed, it has an almost immediate effect on engine operation.

STIHL MS 181 C BE chain saw carburetor

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Great Idea For Your Chainsaw. Simple Invention

Chainsaw carburetors can vary in design. But their basic elements and working principle are about the same.

This is a wind tunnel with an air damper across which the airflow rate is controlled.

This part is where the base tube shrinks. this is where the airflow rate increases, t.е. air is always supplied to the carburetor under some pressure.

In this area there is a contact of fuel with the air flow. The fuel flows to the atomizer from the float chamber through the nozzle (metering device).

It is a container that keeps the fuel mixture in a stable state.

Constructional diagram of a chainsaw carburetor

A chainsaw carburetor works according to the following principle:

  • when starting the engine, the main flap opens and a stream of air is supplied to the air duct at a certain speed;
  • the speed of air flow, as well as the level of the float in the chamber are regulated by the position of the flap, namely due to the pressure difference in the float chamber and the air duct;
  • fuel from the float chamber is sucked into the nozzle and from there into the diffuser;
  • Passing through the diffuser, the air captures the fuel that enters it;
  • the resulting mixture is fed into the cylinder cavities through the intake channels.

The pressure in the float chamber is approximately equal to atmospheric pressure, but in the air ducts of the carburetor when starting the chainsaw engine is rarefaction. Opening the choke causes the airflow rate to increase. As a result, more fuel goes into the carburetor, and the number of engine shaft revolutions increases.

Main faults

Conventionally, all the typical breakdowns of gasoline saws are divided into two large groups:

  • Defects and wear of engine parts. The weakest engine components and units that most often fail and are the first to wear out are the elements of the cylinder-piston group, the exhaust of air mixtures, air and fuel supply, ignition.
  • Faults in other mechanisms. There may be a problem with the lubrication system, the guide bar, the clutch, the emergency brake.

We recommend that you have your power tool checked by trained professionals. Having executed the repair poorly, you risk the serviceability of the engine and the entire chainsaw.

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Troubleshooting the chain brake

The inertia chain brake is designed to switch off immediately if the chain jams or kicks back. The latter occurs when the bar nose or upper part of the bar touches the material to be machined. When the bar is suddenly thrown, the brake stops the chain movement without stopping the motor. Therefore, when the brake is applied, the motor must be switched off and then unlocked.

When the brake is activated the clutch cup on the drive sprocket is blocked. The engine will have enough power to turn the clutch. As a result, its cams will rub against the cup and the mechanism itself will get hot. Plastic components such as the oil pump actuator, clutch cover, etc., could melt.д. If you continue to work with the brake on, you will notice a characteristic smoke and odor, and the saw will most likely have to be repaired. A similar situation can occur when the chain is jammed in the work material, if the operator tries to release it by increasing the engine speed.

If the cap of the inertia brake is melted, it must be replaced. Because without it, the system will not work properly. If the oil pump drive unit is melted, it is no longer possible to supply oil to the chain. Therefore, this element, as well as worn or damaged clutch parts should also be replaced immediately.

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It is a good idea for chainsaw makers to check the parking brake every time you start the engine. If it is defective, tool operation becomes unsafe and its life is reduced, leading to unforeseen financial costs in the near future.

Troubleshooting muffler problems

If the chainsaw is running smoothly at low RPM, but starts to cut off and smoke at high RPM, the problem may be in the muffler.

In order to check the quality of its operation you should perform:

  • disassembly (making sure the exhaust port is closed);
  • disassembly (if the muffler is demountable);
  • Remove soot deposits with special detergents or use the dry cleaning method;
  • drying (using a hair dryer);
  • Reassembly and Reassembly.

Dry cleaning without respiratory protection is not recommended. Carcinogens present in the soot will be released into the surrounding atmosphere in the form of dust, inhaling which is extremely hazardous to health.

To prevent the chainsaw from clogging the muffler when it is in use, you must carefully check the fuel-air mix and the quality of its components.

Cylinder and piston group

It happens that the engine will not start or functions poorly because of low cylinder pressure. Failure can be a failed piston, cylinder or bearings, piston rings sticking out, etc. It is possible to consider the problem in general terms, but to do so remove the muffler and inspect the system.

You can measure the compression in the engine, for this you need to put a compressometer in the spark plug hole. After a while you can draw conclusions from the results of the measurement. Only by completely disassembling the system can the problem be examined. If there are scratches or chips on the piston, it must be replaced. The piston ring must be installed in its rightful place, clean and intact.

Structure and principle of chain saw starter

All types of chain saws, both Chinese and European, are equipped with starters of identical design and operating principle. The universal design of the starters allows to use these devices on branded chainsaws, as well as on the semi-official tools supplied from the Celestial Empire. It is important to note only that some distinctive features have tools of domestic production.

The chain saw starter is an uncomplicated mechanism consisting of:

The principle of operation of such a device is also quite simple. When pulling the handle, which is connected through a cable to the drum of the ratchet mechanism, there is its movement. The crankcase drum is rotating and gets caught in the splines of another drum which is located on the crankshaft. The saw’s crankshaft is thus manually moved and makes several revolutions. As soon as the crank is returned to its original position, which is assisted by the return spring, the spline connection is lost, causing the shaft to stop. Every movement of the crankshaft increases the amount of fuel-air mixture in the cylinder, which eventually combusts.

the more power the tool has, the more jerks the starter has to make to get the motor running. The recoil spring, made from highly resilient steel, is responsible for speeding up the reel’s return to its original position.

Over time, with constant use of the tool, there are problems with starting the engine, or, more precisely, with the functioning of the starter. If such problems occur, the starter can always be repaired. If you know the principle and the construction of the starter, then to carry out its repair with your own hands is not very difficult.

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Заточка цепи бензопилы своими руками. Sharpening chains chainsaw with your own hands.

Tire, chain, chain brake and lubrication

When two of the chains are worn out, the drive sprocket must be replaced. Using a worn sprocket affects the life of the crankshaft bearings and causes strong vibrations, the chain also deteriorates faster. It is recommended to turn the tire as the working part wears.

Brake failure can be caused by excessive contamination of the space under the cover or general wear of the belt spring. It is also common for the clutch to collapse from overheating when the brake is applied and the entire assembly must be replaced.

Lack of lubrication on the chain can cause clogging of the oil pump ducts, it must be washed in gasoline and cleaned with a fishing line. If you get too much oil during work, you need to tighten the oil pump adjustment screw a little. It happens that when working, the chain is dry, and with a simple oil oozes under the clutch. This means that the oil hose is leaking and must be replaced.

Actuator malfunctions

If the malfunction is in the tool chain, you can also fix it yourself, or replace it with a new one.

repair, chainsaw, your, hands

Chainsaw clutch repair

The clutch or clutch on the tool is represented in the form of a centrifugal drum, the actuation of which is automatic. Over time, the clutch will wear out, requiring it to be replaced. The cause of clutch failure is the wear of the teeth of the drive sprocket. If the clutch is in one piece with the crown or drive sprocket of the tool, it must be replaced as a complete unit. If the sprocket separates from the drum, you can replace only the ring gear, which is much cheaper. The clutch requires only periodic lubrication to extend its life.

Chain lubrication system

The chain lubrication system is an important device to ensure a continuous supply of lubricant to the bar and chain of the tool. Trouble with this system is mainly caused by clogged channels. If oil leaks, check the tightness of the tubes connected to the pump connections. Leaks can be fixed with sealant or by replacing the tubing.

Good to know! Never use used oil as chain lubricant.

In conclusion, it should be noted that any breakdown of the chainsaw can be eliminated, and most of them are done independently. If the failure is related to the carburetor or piston-cylinder group, then you need the help of experts. The repair procedure is otherwise much simpler than an automobile engine repair.

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