Repair of the main malfunctions of a chain power saw

The chain power saw is the irreplaceable tool for owners of private houses and dachas. She can cut branches in the garden, cut down trees, cut boards and other wood-based materials. But no matter how expensive and reliable this unit is, the moment will come when minor or major faults will appear in it. Of course, serious damage should be fixed only in the service center. But minor repairs chain saws can often be done personally.

The device and the principle of operation of the chain saws

The device of a chain electric saw differs from the device of a chainsaw only by the type of drive, namely by the presence of an electric motor instead of a gasoline engine. The unit consists of an electric motor placed in a plastic case, a reservoir for lubrication, an oil pump, as well as a tire and a chain having cutting elements (teeth). How the chain power saw is arranged can be seen in the figure below.

Electric saws can be either with a transverse engine (shown in the figure above), or with a longitudinal engine (see photo below).

In an electric saw with a transverse engine arrangement, rotational motion from it is transmitted directly to the drive sprocket. In the apparatus with a longitudinal electric motor, this process is carried out through a gearbox.

An asterisk installed in the same plane with the tire of the unit, rotating, pulls the chain. The latter, mounted on the tire of the unit, slides along it at high speed. Due to the presence of cutting elements on the chain, sawing wood occurs. Since the blade from the electric saw has a wider width than the tire, the tool does not jam in the material, and the cutting process is quick.

To reduce wear of the saw chain and tire on electric saws installed Lubrication system, feeding oil to the saw headset.

The lubrication system includes an oil tank with a volume of about 500 ml and an oil pump. The latter, while the saw is running, continuously applies lubricant to the tire. Further, the lubricant is spread by means of a chain over the entire surface of the tire and falls both on the leading and on the sprocket guide.

The main malfunction of electric saws

Breakage of an electric chain saw does not occur from scratch. Most often they can appear due to power surges in the network, improper operation of the unit, poor build quality of the device. The following can be attributed to the main faults of chain saws.

1. When pressing the start button of the unit the saw won't start. The network cable or the power plug may be out of order. If everything is OK with the cable, the unit may be damaged by a faulty start button, a motor winding blown out, or full brush wear.
2. While working burning brushes on a power sawand a circular light appears on the engine manifold. A malfunction may be caused by worn brushes or an armature winding short circuit.
3. There is no lubrication on the circuit.. This happens if the oil in the tank has run out, the tube or hole that is responsible for the lubricant supply is clogged, or the oil pump has failed.
4. Unit cannot reach full capacity. Possible reasons are as follows: worn brushes; interturn or open circuit of the armature winding; low voltage; the start button failed; there was a jam in the gearbox; brake system malfunction.
5. Electric motor stops during operation. This behavior of the unit may be caused by jamming of the gearbox or wear of the brushes.
6. The electric motor of the device quickly overheats. There may be several reasons for the saw to be heated: high ambient temperatures; poor engine ventilation when running at low speeds; vents for ventilation are blocked or blocked; continuous operation of the unit under heavy load; increased rate of operation of the apparatus without rest breaks; gearbox malfunction; lack of lubrication; damage to motor windings.
7. The unit makes uneven cut. The reason for this may be blunted chain cutters or uneven tire wear.
8. When the motor is running, the chain remains fixed.. The most common failure occurs due to failure of the clutch. Also, this malfunction may occur if the gears of the gearbox and the drive sprocket break.

Electric disassembly for repair

To start troubleshooting yourself, it is recommended that you first learn how to disassemble a power saw. A complete disassembly of the unit using the example of the Makit electric saw is as follows.

1. Flip off the screw, which fixes the tire, and slightly loosen the mount. Next, use the chain tensioner to loosen the saw chain.
   
2. Fully unscrew the tire mounting screw and remove the cover.
   
3. Remove the chain from the sprocket and disconnect the tire from the unit (together with the chain).
   

4. Now you need to unscrew the 2 screws that secure the engine from the sprocket side.
   

5. Also unscrew the pair of screws on the other side of the unit. For convenience, you can remove the cover of the oil tank.
   
6. When all the fasteners are removed, you can disconnect the gearbox from the engine.
   
7. The next step is required remove the sprocket. Since it is fastened with a lock washer, it should be removed using a flat-blade screwdriver.
   

   

8. Remove the locking ring, remove the washer under it, and remove the sprocket from the gearbox shaft. Then twist the 6 screws that secure the toothed lugs and the handle of the device.
   
9. After turning the fasteners, disconnect the stops and the handle from the gearbox.
   
10. Next, you should turn the gearbox and remove the cover.
    
11. Remove the tubing from the pump and remove the oil reservoir.
    

    

12. Press the brake lever in the direction of braking until you hear a click, and remove it.
    
13. Turn the gearbox over and disconnect the aluminum housing along with the shaft.
    

    

14. Under the plastic cover, as well as on the gears, you can see the accumulation of dust, sawdust and grease.
    

    

    

    

15. All gearbox parts needed clean the dirt.
    

    

16. Next, remove the plunger of the oil pump.
    

    

17. Remove the oil pump from the plastic cover of the gearbox.
    
18. Rotating both parts of the pump in different directions, try to gently pull them one from the other. After the pump is disconnected, a ball and a spring will fall out of it.
    
19. Next, you need to disassemble the brake mechanism. Put the lever on and turn it until it clicks. Spring tension in this position of the lever will be minimal.
    
20. Pry the spring with a screwdriver and remove it from the aluminum housing.
    
21. Together with the spring, remove the thrust.
    
22. To remove the brake band, unscrew the retaining screw.
    

    

23. Before assembly to the pinion gear grease required. This can be done as shown in the following photo. When the unit is operating, the lubricant will spread through the gear teeth due to centrifugal force.
    
24. The next step is required disassemble the motor housing. Remove the gear mounted on the motor shaft.
    

    

25. Remove the electrical brushes and unscrew 6 screws on one side of the case and 1 screw on the other.
    
26. Remove the cover.
    
27. Remove the motor rotor with a slight force.
    

    

At this complete disassembly of the unit can be completed. Assembling electric saws in reverse order.

Algorithm of diagnostics and repair

Starting to repair a chain power saw, it is necessary to conduct a consistent diagnosis of all units of the unit to determine the cause of a breakdown. Repair of the unit is carried out, based on the symptoms of faults that were listed above. Below is the power saw, which shows in detail the internal structure of the unit.

Power saw does not turn on

If the unit does not turn on when the start button is pressed, the diagnostics are performed in the following order.

1. Check out voltage in the outlet. It may not be due to a general disconnection or malfunction of the outlet. Try switching the unit to another place.
2. If there is voltage in the outlet, then it is worth checking network cable. Remove the motor housing cover and ring each wire with a tester, touching one probe to the contact inside the unit, and the other to one of the rods of the electrical plug.
3. If the wire is fine, then continue to check further. Call the tester wires to the start button for a break.
4. Next, you should call button contacts at the entrance and exit when the key is pressed.
5. After that check conductorsgoing to the engine unit. If a softstarter is in their way, then check the circuit at the entrance and exit of it.

If the previous steps did not reveal the cause of the engine failure, then the brushes should be removed and checked. There are cases that the engine does not start due to the complete wear of one or both brushes, as well as due to the break of the conductors in them. If the brushes are in good condition, then most likely, the engine has failed, namely, the stator or rotor windings have burned out. In this case, in order to ring the coils, it is necessary to have some skills and knowledge in this area. It is better to take the power saw engine to a specialist who finds the fault and produces rewind reels.

Burn brushes and collector

The appearance of strong sparking under the brushes can be caused by poor contact between the armature lamellae and the electrodes due to their wear. To check this, it is necessary to remove the parts from the brush holders.

It is believed that the normal wear of the brushes should be no more than 2/3 of their original length.

If the brushes are worn, they must be replaced. Brushes can also spark due to clogging of the gap between the anchor lamellas. graphite dust. Since graphite is a conductor, it causes closure and the appearance of sparks.

To eliminate contamination, it is necessary to clean the lamellae well with alcohol, cotton wool and a toothbrush. It is also recommended to polish them with the smallest sandpaper (null).

No lubrication on the chain and tire

Lack of lubrication on the tire or lack of it can be caused by clogging of the hole or tube through which oil is supplied to the tire.Often the chain is not lubricated if the supply of lubricant from the tank is disrupted. This can happen when filter clogginginstalled at the end of the hose. The latter is always inside the tank. To eliminate the problem, you must pull the hose out of the oil tank and rinse the filter with gasoline.

Breakdown of the oil pump It may also cause the oil not to flow to the power saw chain. After cleaning the filter, hose and lubrication holes, turn on the power saw and observe whether the lubricant enters the tire, provided that there is enough oil in the tank. If the lubricant does not arrive, it is necessary to remove and disassemble the oil pump, check the serviceability of the spring or its other parts (depends on the model of the unit) and, if necessary, replace it with a new one.

The engine gets very hot

The cause of the engine overheating can be gear wrench jammingif it is heavily contaminated with small sawdust, or if there are foreign objects on it, for example, fragments of a spring or plastic parts.Try rotating the gearbox shaft manually with the brake off. If the rotation is difficult, then you need to disassemble the gearbox and fix the problem.

Motor overheating can also cause motor breaks. In this case, repair the engine with your own hands will not work. You will need to seek help from a specialist.

Also, the engine may overheat if no oil is fed to the saw chain. This leads to poor slip tooling on the tire, and as a consequence, increased load on the electric motor. How to diagnose and eliminate this fault, it was described above.

Engine does not develop full power

First of all, you need to check the mains voltage. It can sometimes decrease and lead to a drop in the power of the unit. Also, the drop in power is caused by jamming the gearbox or the wear of the brushes. How to fix these problems was discussed above.

Causes similar symptoms and faulty start button. If the tester detects a malfunction when checking this part, then it will not be repaired. The button must be replaced with a new one.But if the verification of the above reasons did not produce results, then it remains to be suspected that the armature windings have burned out or an interturn short has occurred in them.

The unit stops during operation.

If the unit stops during operation, then a full wear of one or both brushes. Checking it is quite simple: remove the brushes from the holders and check their length.

Sometimes there are brushes with a short conductor inside the pressure spring. In appearance, such a brush will have a sufficient electrode length, but if you look closely at the spring, it will not be fully decompressed due to the short conductor.

Also, the unit can stop in the process of work, if there are faults in the gearbox. In this case, you will hear a buzzing engine that will not be able to rotate. Often, stopping the unit causes end sprocket seizurelocated at the end of the tire due to clogging. The main task of the sprocket is to move the chain around the top of the tire. As is the case with the breakdown of the gearbox, you will hear the hum of the engine. Check the jamming of the sprocket can be,if the unit is turned off and the brake is depressed, try to manually stretch the chain: if it does not move, it means that it is stuck in the tire.

Some tire models have a collapsible design that allows you to replace the end sprocket on the power saw tire when it is worn or to replace the bearings. If your machine is installed fixed tire, then try to clear all the space near the asterisk with a thin wire and some penetrating liquid, for example, kerosene or WD-40. After cleaning and lubricating the part, try turning it. If the sprocket turns with difficulty or does not turn at all, it means that the bearing is damaged. In this case, the tire must be replaced.

Power saw not exactly

If the electric saw leads away, then in most cases this is due to one-sided tire wear. The chain, passing on such a tire, is warped, and the headset produces uneven kerf. If you look at the tire, it will be erased on one side more than on the other. The problem is solved by replacing the tire as well as the chains and sprockets, which also have been subject to uneven wear.Even if a new tire is installed on the unit, the previously worn parts will quickly destroy it.