Many tools require regular replacement of consumables. It concerns and drank. That is why the question of how to remove the sprocket from a chainsaw, which is also often called the clutch disc or centrifugal mechanism, is very relevant for home craftsmen. In this regard, it is necessary to consider what is called an asterisk and why it is needed.
The clutch drum, called the sprocket, is an integral part of the chainsaw.
Chainsaw sprocket device
An asterisk or centrifugal mechanism is a part resembling a star in shape. It takes over the engine torque and transfers it to the guide and saw chain. This guarantees the rotation of the cutting headset and the cutting process itself. It works in automatic mode, which depends on the magnitude of the engine speed.
The clutch drum can be localized both outside the chainsaw and on its inside under a separate cover. It performs a protective function not only in relation to the material of which the sprocket is made, but also for the operator, who may be injured by it during operation.
In addition to the function of chain rotation, the leading star of the saw prevents the appearance of malfunctions of the motor system in those cases when the chain is jammed or stops rotating.
Features of the clutch drum in chainsaws
The drum, located at the base of the clutch mechanism, is an integral part of the chain drive system. This detail resembles a star in its shape, due to which it got its name. Depending on the type of chainsaw, the part can be professional or household. Since a professional saw is used more often than a household saw, the leading sprocket requires regular replacement. If we talk about household tools, then everything depends on the amount of work performed and the load that is on the device circuit.
Most often, the sprocket, crown and saw bearing require replacement.
In any case, the main reason for replacing the sprocket is the wear of its teeth on the chain. In the case when a monolithic drum is installed in the device, the surface of the chain cuts through it almost completely, which requires a complete replacement of the entire part. If the chainsaw has a drum with a replaceable crown, here you can limit yourself to replacing the crown.
Usually, in order to remove an asterisk from a chainsaw, many people turn to specialized service centers, but if there is a need to save the family budget, you can do this work yourself. This event does not look complicated, but you need to have all the necessary parts and tools. The sprocket replacement process is the same for any device model.
The main reasons for replacing the drive sprocket
The universal key is the main tool that will be required when replacing the sprocket.
The most common causes that force you to repair the tool associated with replacing the drive sprocket are:
- jamming of the chain due to the occurrence of defects during operation of the unit;
- high sprocket wear as a result of long-term operation of the unit.
With the regular use of the device, there is increased wear of the sprocket as a result of increased loads on it during the sawing of wood. There are two ways to operate the device:
- use of one saw chain;
- the use of several saw chains alternately.
When applying the first method of operation, the chain is operated until complete wear. This method has several disadvantages. The main one is the problem of wear control during intensive operation of the unit.
When using two or more chains in the process, it is possible to achieve uniform wear of the chains and sprockets, which allows to extend the period of operation of the device until repairs are carried out, consisting in replacing the sprockets. In addition to the wear of the sprocket, one should not forget about the bearing, which is installed in the sprocket. This structural element works at any engine speed. When replacing sprockets, the bearing should be changed at the same time.
The coupling complete with an asterisk should be replaced in a timely manner. In case of untimely repair work during operation, the tool experiences increased vibration, which leads to increased wear of bearings installed in the internal combustion engine on the crankshaft axles. The maximum depth of wear of the sprocket teeth should not exceed 0.5 mm. The sprocket’s service life is twice that of one chain, so two chains should be used during operation. After the life of the chains is reached, a simultaneous replacement of the chains and the drive sprocket should be carried out.
Chainsaw Sprocket Design
In the design of the chainsaw there is not only a leading, but also a driven sprocket. The chainsaw drive sprocket is located in the tool structure, and the driven sprocket is located at the end of the tire. The purpose of the slave device is to equalize the tension and direction of movement of the chain device.
Driven star on tool bar
Leading devices are integral and prefabricated. Whole products consist of a hub with a pressed gear rim. When replacing, the entire assembly is dismantled, since the gear structure is one-piece. From the factory, chainsaws of many famous brands are equipped with integral gears.
How does a whole gear on a chainsaw look like?
Collapsible products are more advanced, since the process of replacing them is simplified by the simplest design of the mechanism. Only one crown changes, the cost of which is 2 times less than the assembly mechanism. Determine the appropriate wear of the gear teeth by the following criteria:
- The presence of large radii in the places of transition of the teeth
- Uneven tooth width
- Detection of chips and metal chips on top of teeth
- Scuffing and risks on the inner surface of the holes in the hub
- When the tool starts, a wedging of the chain is detected
If the master device is worn, it must be replaced. You can do this yourself, for which the tool is initially disassembled, and the version of the installed device is determined. Even if a non-separable gear is installed on the tool, then a prefabricated mechanism can be installed instead, which is more rational.
Collapsible gear type for chainsaw
There are two types of installation of leading stars on chainsaws. The first method involves the location of the gear from the outside. Such designs are most common on Stihl chainsaws. The design of such a device is shown in the photo below.
Non-separable product on the instrument
The second option is inherent for instruments of Chinese origin. The gear teeth are not located on the outside, but on the inside, that is, the device is located on the contrary.
Star design on a Chinese chainsaw
Depending on the design of the tool, the process of dismantling the products in question will differ.
It is interesting! In order to extend the service life of the drive gear of the chainsaw, it is necessary to run-in the tool, and during operation do not overload it, which depends on the purpose (household, semi-professional or professional). A household tool can cut a tree, but the saw is not intended for this, and its frequent use with overloads will lead to wear of component parts.
Classification of the leading chain saw chains
In accordance with the power class of the saws on which they are installed, the asterisk can be:
The main difference between them is the frequency of replacement and the rate of wear: in the Pro series, wear is faster and repairs are more frequent.
By design features, the leading chain saw stars are:
The latter consist of a hub with a stationary crown of a certain number of teeth. Their factory fitting does not allow to remove the crown separately from the hub. This situation is typical for many Chinese chainsaws, for example, from the Champion brand.
The situation with prefabricated sprockets is simpler: a removable crown quickly unscrews from the axis of the drum, so repair is not particularly difficult. This option is the advantage of most saws of European origin, for example, “Stihl” or “Husqvarna”.
Replacing the sprocket on a Chinese chainsaw
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How the star on a chainsaw is removed and changed
Before you remove and replace the star on the chainsaw, you need to make sure that the part is not subject to further operation. To do this, you need to inspect the part, and a photo of the new and worn chain saw sprocket is shown in the photo below.
To change the gear, you need to decide what kind of device is on the tool, and what will be installed. For each type of mechanism, the sequence of actions will be different. Replacing the sprocket on a chainsaw of the first non-separable type is as follows:
- Dismantling the casing as well as tires and chains
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Removing the retaining ring, and after it the washers
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Dismantling the snap ring
In the reverse sequence, the assembly process of the mechanism is carried out. If you need to replace a collapsible product, the process will be almost the same, only as a result, one crown without a drum is replaced.
Design differences gears integral and collapsible type
If the replacement process is completed, you need to check. The chain tension is checked, for which the hand brake is applied, and the chain is pulled in the direction of its movement. The immobility of the product indicates the constriction of the mount. To loosen it, you will need to release the tensioner.
It is interesting! When replacing the mechanism in question, it is recommended to buy a special suitable repair kit for a specific model of the tool, depending on the chain pitch.
Replacing Worn Parts
If the gear has a removable crown, carefully check the condition of the base. If nicks, chips, deep scratches, geometry changes or corrosion are detected, not only the crown, but the entire part should be replaced. Joint work in the same unit of worn and new parts will lead to a reduction in the service life of the entire unit. Significantly increases the risk of jamming or breaking the chain.
In addition, the vibration load on the clutch, transmission and engine of the device will increase. The same factors arise during the continuous operation of a single circuit.
Folk "craftsmen" sometimes reanimate the stretched web of the chain, simply throwing one for the link and re-pressing the axis. In this case, the chainsaw requires a sprocket replacement.
You should also not change the diameter of the gears (and, accordingly, the number of teeth). When working with an enlarged or reduced asterisk in the transmission and engine, forces arise that the device’s designers did not expect. This will reduce the operational life of the tool and not increase its productivity.
Despite the presence of safety systems in the design of the chainsaw, which instantly stops the movement of the blade when it breaks or the tire breaks and protects torn links from flying apart, it is better not to bring such situations. The need to replace gears is only enhanced by safety requirements.
Criteria for choosing a repair kit yourself
The desire of the owner to equip the headset with a saw chain with another step, leads to the need to change the asterisk to a part with a crown of the corresponding profile. This requirement applies to the entire range of European and Chinese chainsaws.
The operational reliability of a European-assembled saw, when operating in difficult conditions of increased loads, can significantly deteriorate if, instead of the original part, a Chinese asterisk is used.
Design features of leading stars
The pitch of the teeth of the drive gear is one of the main parameters of the assembly. It must coincide with the pitch of the chain links and, no less important, with the pitch of the teeth of the driven sprocket located at the end of the chainsaw tire.
Drive gears by design features are divided into:
Experts identify the following signs of wear of the teeth of the drive gear:
- semicircular cavities are noticeable at the base of the tooth;
- tooth thickness varies with height;
- cleaved areas on top;
- scratches appeared inside the hole in the hub;
- the chain rubbed a groove in the sprocket;
- when starting, the chainsaw wedges.
The chainsaw sprocket with such signs should not be operated, it must be removed and replaced.
According to the manufacturer’s recommendations, the tool should be inspected before starting work. In this case, the condition of the saw bar must be checked whether it is securely fastened. If the screw adjusting the position of the roller of the chain and its tension is loosened, or if the nuts fastening the tire to the casing are loosened, it deviates from the plane of the chain. In this case, the rollers of the blade do not rest on the middle, but on the edges of the teeth, increasing the load on them and on the chainsaw as a whole. Increased wear leads to premature failure.
Sprockets with removable and stationary crown
After tightening the mounts and adjustments make a trial run. If the free play remains, then the sprocket will have to be removed and replaced.
Removal and replacement process
The method of removing the sprocket will depend on the design of the chainsaw. Chainsaws can be divided into two types according to the location of the leading star:
In the first case, the removal process is somewhat simpler. To do this, you just need to remove the snap ring with a screwdriver, after which the sprocket is easily removed.
In the second case, you first have to remove the clutch. To do this, stop the shaft on which it is located. There are two ways to do this:
- Or unscrew the candle and tighten the special piston stopper instead, which would prevent the latter from moving.
- Or, from the starter side, insert a suitable wrench or screwdriver into one of the available holes to lock the impeller there. True, this method is dangerous because often the sprocket is tightened quite strongly, because of which it is more likely to break the impeller blades than to unscrew the star. Therefore, if you do not have a stopper from the previous method, then use the alternative method from the next paragraph.
- The folk way is that instead of a special stopper, it is possible to push a piece of fabric into the combustion chamber through the hole where the candle is wrapped, leaving a part of the fabric so that it can then be pulled out. The fabric will occupy the entire space inside and prevent the piston from moving upward, due to which the shaft will stall. over, due to the fact that the fabric itself is soft, it will not cause any damage to the walls of the cylinder.
After the shaft is locked, you can unscrew the clutch. You need to use either a special puller, or you can get by with a suitable open-end wrench by inserting it into the recesses on the clutch. Loosening is done clockwise, since the thread on the shaft is left.
Unscrewing the clutch, you can now easily remove the sprocket.
When changing a star, it is also necessary to change the bearing below it. Usually they are sold in one repair kit.
The installation of new parts must be done in the reverse order.
As you see, nothing complicated. everyone can handle it.
Clutch drum replacement algorithm
The chainsaw clutch closes the sprocket.
First of all, it should be noted that when buying spare parts for a chainsaw, you must strictly observe the type of drum or consult a specialist if it comes to its modernization. As a rule, while replacing the drum and the saw chain, the drum bearings are also replaced.
Here you should purchase a special repair kit, which provides for the presence of a drive sprocket and bearing. Then you should prepare the tool and the details that will be required for the work:
- universal key, sold complete with a chainsaw;
- mechanism piston stop (in standard cases it is plastic or metal);
- centrifugal or clutch puller (selected depending on the model of the chainsaw).
During the operation, the following actions are performed:
Chainsaw sprocket location scheme.
- First, the saw headset is removed, the nuts of the tire cover are unscrewed using a universal key. The cover is removed, the tire and chain are removed.
- After that, the air filter is removed.
- Using a universal key, the saw candle is twisted. Instead, a prepared piston stop is inserted, which allows you to fix the position of the piston in the cylinder.
- The clutch puller is installed in the universal key connector. Then, using the resulting device, the clutch is unscrewed. All actions must be carried out clockwise.
- The clutch is removed, freeing up access to internal parts. Now you can remove the sprocket (clutch drum).
- Depending on the type of drum, it is inspected or checked. An asterisk or crown changes to new ones. When installing new parts, carefully check the condition of the clutch separator. Particular attention should be paid to centrifugal springs and cams. If strong wear is detected, these parts also need to be replaced.
- If the condition of the parts is not satisfactory, all parts of the chainsaw are assembled in the reverse order. First of all, the piston stop is twisted, the starter cord is pulled out, then the stop is screwed again. Such complex actions allow you to clamp the centrifugal mechanism of the chainsaw on the crankshaft.
- Using the universal standard key, the clutch is clamped counterclockwise, that is, against chain rotation.
- After that, all the nodes and parts can be successfully screwed into their original places.
In order to replace the sprocket on the chainsaw, all work must be done carefully and carefully.
Without the availability of special tools, repair work may fail: not only a star or a centrifugal mechanism may break, but also a saw chain.
As can be seen from the information presented, the question of how to remove the sprocket from the saw can be successfully solved on its own. Once the operation is carried out, it will be possible to carry out it again and again, as soon as the need arises, and attention and accuracy will be the key to competently completed work.
How to remove an asterisk from a chainsaw: several options for different designs of the clutch drum
The method for a star with a stationary crown
To do this, produce:
- dismantling the protective cover and tire-cutting headset;
- locking of the piston of the motor;
- disconnecting the clutch from the motor system;
- recess from the saw body of the clutch and the centrifugal sprocket;
- visual inspection of the sprocket and its gear part;
- if defects are detected, replace the sprocket with a new clutch drum;
- diagnostics of clutch chainsaw elements for defects. worn centrifugal springs and cams can adversely affect the operation of the sprocket;
- if there are no malfunctions, we proceed to the assembly stage. To do this, you need:
- remove the stopper;
- to pull off the ignition cable;
- screw the stop to fix the centrifugal mechanism on the motor shaft;
- use a universal key in the direction against the chain stroke to tighten the clutch;
- return the remaining removed parts to their previous positions.
Method for star with collapsible clutch drum
The second method regarding how to unscrew the sprocket on a chainsaw with a collapsible clutch drum looks simpler than the previous one. The sequence of actions will be similar, but not the entire star will be subject to disassembly and reinstallation, but only a separate part of it. the ring gear.
Do not forget that the installation of a new chain on the tire chainsaw is one of the reasons to re-equip the saw with a new asterisk. Otherwise, the chain will stretch ahead of time or break during operation. Less wear on the clutch drum results in alternate use of several chains and periodic maintenance of its bearing. This mechanism is used exclusively at idle: with an increase in speed, it is not involved in the work. Experts recommend changing it simultaneously with a chain and an asterisk and systematically lubricating it with chain oil.
how remove the lead an asterisk with a chainsaw?
As already noted, the sprocket can have a separate and pressed crown. Therefore, the sequence of actions will be different.
For a stationary crown located sequentially produce:
- Dismantling the casing;
- Removing the saw bar with chain;
- Disconnecting the clutch from the engine (the piston should first be locked);
- Removing the clutch together with the drum;
- Removing the crown from the drum using an ordinary open-end wrench (some manufacturers also attach a puller to the spare parts kit).
Assembly of the unit is carried out in the reverse order. For some models, before dismantling the crown, take off also an air filter.
When disassembling the drive sprocket for a chainsaw, which has a removable crown, the procedure will be almost the same, but at the final stage it is only necessary to replace the crown.
After completion of work, it is necessary to check the effectiveness of the replacement. To do this, check the chain tension: if the brake is released and an attempt is made to pull the chain in the direction of its movement, it is stationary, then the fastener is “tightened” and the tensioner should be slightly released.
The success of the work is determined by the presence of a special repair kit purchased for a particular brand of chainsaw. To push the carburetor off, you now need to remove the Stihl 180 chainsaws, as well. Otherwise, you should know exactly the size of the saw and tooth pitch.
How to replace with your own hands
Experienced craftsmen recommend the following sequence of operations when replacing an asterisk:
- Remove housing and air filter (if necessary).
- Unscrew the spark plug and insert a latch instead to lock the piston.
- Remove the chainsaw clutch.
- Remove the gear with a puller or open-end wrench.
The removable crown should be unscrewed clockwise. If during disassembly it turns out that the parts of the centrifugal mechanism are worn or broken, you should also remove it and replace it. If parts and assemblies are not visually damaged, then the assembly of the mechanism is carried out in the reverse order.
How to remove an asterisk from a chainsaw yourself
To correctly and accurately fix the clutch mechanism on the drive shaft, remove the piston lock, gently pull on the starter cord and release it.