Clutch Replacement On A Chinese Chainsaw
One of the most important components of a chainsaw is a clutch or clutch mechanism. When using the tool, this part may fail, which will entail the inability to carry out work on sawing wood. If the clutch mechanism is out of order, the question immediately arises of how to remove the clutch on a chainsaw. This need arises when you need to repair or replace the device. How to do this is described in the material.
Design and principle of operation of the chainsaw clutch mechanism
Most sawyers do not understand the principle of operation of the chainsaw clutch mechanism. At work, it is not necessary to know the principle of operation, but when malfunctions arise, in order to eliminate them, you will need to find out the design and features of the chainsaw clutch.
Modern chainsaws are equipped with centrifugal clutch mechanisms. Centrifugal clutch. This means that its performance depends on the torque of the engine. The main purpose of the clutch on a chainsaw is to ensure the transmission of torque from the crankshaft of the engine to the saw headset (chain). The device works in automatic mode, and how this happens, we find out in detail.
The clutch mechanism consists of the following structural elements:
- A drum with a removable or non-removable sprocket. Is a gear
- Friction linings. Under the influence of centrifugal force, they move, entering into engagement with the drum
- Spring. Provides pressure pad to the crankshaft
Now about the principle of operation of the chainsaw clutch. When the two-stroke engine of the tool starts, the crankshaft begins to rotate. A coupling is attached to the shaft, to which a chain is connected with an asterisk. When the chainsaw is idling (shaft speed up to 2700 rpm), that is, the accelerator trigger is not pulled, the spring presses the friction linings, as a result of which the torque is not transmitted to the drum.
As soon as the sawyer picks up the tool and starts to increase the speed (maximum up to 14000 rpm), the chain begins to move along the tire. This happens due to the fact that the rotation speed of the crankshaft increases. Due to the inertia force, the friction pads (also called counterweights) are moved and mesh with the inner walls of the drum. As a result, the drum moves, which is connected to the sprocket. A spinning sprocket drives a chain.
The principle of operation of the mechanism is simple, due to its not complicated design. If this part fails, then the chainsaw will not work accordingly. A detailed description of the operation of the chainsaw clutch mechanism is described in this material.
When clutch replacement is needed
Removing and replacing the clutch of the chainsaw is carried out in case of detection of a malfunction of the mechanism. These malfunctions include:
- Damage to the spring. Depending on the model of the tool, the spring can be presented in two types. A coil (tape or single) or a steel plate. A spring is damaged by tension, separation, or mechanical defect. To determine the cause of the failure of the entire mechanism, you will need to remove the protective cover and drum
- Damage and production of the drum. Breakage of this part is often associated with chipping pieces. With such a malfunction, you will need to replace the drum. The inside also wears out on the drum, so the part also needs to be replaced. If the drum is blue, then this indicates that it has been overheated and should not be used again.
- The development of the mechanism. It is connected, first of all, with the extension of the spring, which can be replaced. The threaded connection also wears out. With such a breakdown, it will be necessary to replace the entire coupling
- Asterisk wear. Depending on the type of sprocket (collapsible or non-collapsible), it is replaced with the drum and, if necessary, with a clutch
The service life of the clutch mechanism depends not only on the quality of the components, but also on the correct operation of the tool. In order to extend the clutch chainsaw service life, you must pay attention to signs that reduce the resource. These signs include:
- Frequent jamming or biting of a chain in wood. In such situations, the clutch takes over the entire load, thereby protecting the engine from jamming
- It is forbidden to increase speed when the hand brake is on, which also leads to wear of the mechanism due to overheating
- The use of low-quality oil, the wrong choice of tires, chains, etc. All this also affects traction, increasing the load, and thereby reducing the operational life.
Determining the malfunction of the device is quite simple. To do this, cut the workpiece. If during the sawing process the chain rotational speed decreases or stops when the load increases, then it is time to check the clutch. How to remove and replace the clutch on a chainsaw, we will consider in detail in the next section.
Removing and replacing the coupling with your own hands according to the instructions
Not many sawers know how to remove the clutch on a chainsaw. The design of the mechanisms on different models of chainsaws is different, but the principle of operation is the same everywhere. The dismantling procedure is also almost identical, therefore, we will further consider how to unscrew the coupling on a chainsaw with an internal sprocket arrangement.
Initially, you will need to prepare the necessary tools:
- A special key called a puller. It often comes with a chainsaw.
- Screwdriver for unscrewing the screws that secure the protective cover
- Candle wrench. Used to unscrew the casing and tire mounts (comes complete with the tool)
- Rope. In order to stall the crankshaft. It is better to use asbestos, but any one is suitable for this purpose. A rope is used in the event that a special piston lock key is not included with the tool.
If dismantling is carried out for the purpose of replacement, then accordingly it will be necessary to prepare a new mechanism in advance. When buying a new coupling, you only need to know the exact brand of the chainsaw, since the devices differ in outer diameter, thread and design of the working mechanism. The instruction on how to remove the clutch on a chainsaw is as follows:
- Initially, unscrew the casing and tire mounting nuts.
- Remove cover with handbrake as well as chain and tire
- After that, we proceed to remove the plastic cover to get to the spark plug. To do this, fasteners are unscrewed with a screwdriver and the cover is removed along with the air filter
- The chainsaw spark plug is unscrewed with a candle key
- Insert a rope into the candle hole in the cylinder (install a special key if one is available). This is done in order to stall the crankshaft. If the diameter of the rope is several times smaller than the size of the candle hole, you can make knots on it
- Next, proceed to unscrew the coupling itself. To do this, take a special key, which should be included. If there is no key, then you can use the tool from the angle grinder or make an independent puller, which is also not difficult
- The key splines must be installed in the holes of the coupling, and then proceed with the rotation of the part. It is necessary to rotate in a clockwise direction. Usually manufacturers indicate directions for unscrewing in the form of an arrow
- When the clutch rotates, the piston reaches top dead center, after which the crankshaft will lock. Further, applying a small force, the clutch will be torn off, followed by unscrewing the mechanism
- The twisted coupling is dismantled from the chainsaw. If necessary, a drum with an asterisk is also removed.
The procedure is not difficult at all, and does not take much time. Assembly is performed in the reverse order of removal. In order to avoid any malfunctions, it is recommended to install a completely identical clutch on the appropriate tool model.
Clutch removal on Stihl and Dolmar chainsaws
Surely you noticed that chainsaws can have different designs of transmission devices. Above is an instruction for removing the clutch with a drum on which the sprocket is on the inside. Such a device is available in most chainsaws, but not on Stihl tools. Chainsaws of a well-known manufacturer are equipped with a drum, which has an asterisk on the outside. It looks like this, as shown in the photo below.
Another arrangement of the sprocket does not mean at all that the tool is equipped with a different clutch mechanism. However, this suggests that the principle of removing the clutch is different from the above instructions. Therefore, we will find out how to remove the coupling on the Stihl, Dolmar and other chainsaws, on which the sprocket is located on the outside.
- First, you must also remove the casing and the tire to ensure access to the coupling
- Unscrew the candle and lock the piston with a special key or cord
- Next, proceed to the removal of the sprocket and drum. To do this, use a screwdriver to pry off the circlip and remove it
- The drum with the bearing is dismantled
- Using the key on “19” (supplied with the tool), it is necessary to unscrew the nut with the left thread, connected to the mechanism. Unscrew in a clockwise direction
- After that, you can carry out the corresponding repair or replacement of the part
Installing a new or repaired part is performed in the reverse order of removal. The procedure is almost identical with the first option, with the exception of some features. If you need to replace only a drum or an asterisk, then you will not need to dismantle the clutch, in contrast to the version with an internal star arrangement.
Clutch Repair. Spring Replacement
Do not rush to change the whole mechanism, since the clutch malfunction can be eliminated by replacing the defective part. Most often, the cause of the malfunction is a spring, which stretches and can be damaged. An already extended spring is defective. If the spring has damaged, it can be replaced to restore the tool to working. The replacement instruction depends on the design of the mechanism, since the compression devices are of different types, but all of them must be replaced. This procedure is not so much complicated as it requires special care and adherence to a sequence of actions. How to replace the spring on the clutch of a chainsaw is shown in detail in the clip.
If the friction pad is damaged, this part can also be replaced. Replacement of the part is also necessary in case of wear of the threaded connection, which happens with frequent removal and installation of the coupling in place. To understand the cause of the malfunction of the part, you will first need to make a visual inspection. If the teeth of the sprocket are worn, then it should be replaced. Fixed stars must be changed with the drum.
What does the adjustment of the clutch of a chainsaw mean and how to carry it out
If you have heard that the clutch on the chainsaw needs to be adjusted, then the question probably arises, how to do this? On a chainsaw, the coupling does not need to be adjusted, since it works in automatic mode, unlike devices of old brands of tools. It is impossible to regulate the compression force of the spring or springs, and if this part is damaged, it should be replaced.
When installing the chainsaw clutch in place, it also does not require any adjustment. The coupling is tightened with a special key and a locked piston in the cylinder. On some models of chainsaws there is a washer or spacer bar. It may be between the shaft and the sprocket, or the drum and the sprocket. This washer adjusts the alignment of the sprocket with the tire. If there is such a washer on a chainsaw, then it must be put in its place when carrying out repairs or replacing the mechanism.
How the clutch mechanism on Ural and Druzhba brand chainsaws is removed and adjusted is shown in detail in the clip.
To summarize, it should be noted that clutch on a chainsaw plays an important role. This mechanism not only provides the transmission of torque from the engine to the circuit, but also protects the motor from premature failure. Imagine a situation where the sprocket is rigidly connected to the crankshaft. When the chain seizes in the material being cut, the engine parts, sprockets and chains will wear out simultaneously. Understanding the purpose and principle of operation of the mechanism, it is always necessary to monitor its serviceability, and at the first sign of failure to carry out removal, repair or even replacement.