Husqvarna 240 Chainsaw Sprocket Replacement

Recommendations: how to remove an asterisk from a chainsaw

  • Features of the clutch drum in chainsaws
  • Clutch drum replacement algorithm

Many tools require regular replacement of consumables. It concerns and drank. That is why the question of how to remove an asterisk from a chainsaw, which is also often called a 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.

Husqvarna 240 Chainsaw Sprocket Replacement

The clutch drum, called the sprocket, is an integral part of the chainsaw.

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.

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 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.

  1. 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.
  2. After that, the air filter is removed.
  3. 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.
  4. 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.
  5. The clutch is removed, freeing up access to internal parts. Now you can remove the sprocket (clutch drum).
  6. 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.
  7. 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.
  8. Using the universal standard key, the clutch is clamped counterclockwise, that is, against chain rotation.
  9. 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.

Husqvarna 137 chainsaw. Clutch drum replacement

The chainsaw clutch drum is one of the most common consumables in a chainsaw, because it is it that drives the cutting chain. The drums themselves are divided into two types. With a welded drive sprocket and with a replaceable crown, and in the second case only the replaceable crown wears out, the drum itself changes much less often.

When repairing the chainsaw clutch, we follow the rule. When the two chains are completely worn out, the tire changes, when the two tires wear, the clutch drum changes. The wear level of the sprocket can be determined without special tools, just inspect it. The chain, moving at high speeds, eventually wipes the teeth along which it moves. If the wear is strong enough, then replacing the clutch drum of the chainsaw is inevitable.

The article will talk about the Husqvarna 137 chainsaw. Replacing the clutch drum is a simple procedure and takes place in several stages.

  • First you need to remove the tire cover and chain brake. To do this, use the combination key that comes with the chainsaw.
    Then we remove the air filter cover, unscrew the spark plug, and lock the piston of the Husqvarna 137 chainsaw. It is recommended to use a normal rope for this procedure, since there is a risk of breaking the piston when using a metal stopper.

How to remove an asterisk from a chainsaw: self-replacement

Today, almost every resident of a country house or cottager has his own chainsaw. You can not do without it with regular logging, gardening and municipal work. The demand for chainsaws is not falling, but even growing due to the fact that these devices do not require much knowledge and skills to work. The only thing that needs to be done regularly is to carry out technical inspections.

As with any other tool, chainsaws require careful personal care. It is necessary to constantly check the oil supply to the chain, the chain tension, the operation of the brake, ignition system and other things. Fortunately, almost any malfunction can be resolved at home on their own.


Like it or not, breakdowns still occur. But it’s important not just to repair the device, but to determine the root cause.

The most common problems:

  • Oil is leaking due to a violation of the integrity of the oil hose or its sealing at the attachment points.
  • Oil does not enter the chain due to clogging of the feed channels with dust and chips.
  • The engine does not start or starts and immediately stalls due to unregulated / malfunctioning carburetor, clogged nozzle, air filter, muffler.
  • The chain wedges due to defects in the drive sprocket.
  • The engine is choking due to a malfunction of the carburetor and a large fuel supply.

Do-it-yourself chain sprocket replacement on a chainsaw

During the regular operation of the chainsaw, the asterisk shown in the photo experiences heavy loads, in connection with this, it often fails. An asterisk, or otherwise a clutch drum, is an important and integral part of a chainsaw that transfers rotational energy from the drive to the chain.

Considering the safety of the drive sprocket and chainsaw chains, there are two ways to operate:

  • Use only one chain
  • The use of two or more chains alternately.

In the first case, the chain can be operated until it is completely erased. However, there are a number of inconveniences. Using only one chain, it is problematic to monitor its condition during intensive work. Hit on nails or other metal parts makes it necessary to edit the chain, but since it is one, the work is slowed down.

In the second case, the alternation of chains allows uniform wear of the sprocket and chains.

In addition to the wear of the sprocket itself, do not forget about its bearing, which operates in idle mode. Therefore, very often they do not pay attention to him and forget to lubricate.

Usually, when replacing a drive sprocket, they immediately try to replace both the bearing and the chain. This is done due to a change in the chain pitch as a result of intensive work.

The procedure for changing the asterisk on a chainsaw with your own hands

There are manys on the Internet that demonstrate how to replace the clutch drum (asterisk) of such famous brands as Stihl, Husqvarna, Druzhba, Ural and others. Finding them is easy.

Each type of chainsaw has its own design features, but the principle of operation is the same, so the general idea comes down to such actions:

  1. The chain brake cover is removed. In this case, the brake should be pulled over so that the brake band does not come into contact with the clutch cup. Next, loosen a pair of nuts holding the cover. The chain tension is loosened, allowing the cover to be completely removed.
  2. The tire with a chain is removed, along with any dirt is removed.
  3. Now you need to fix the piston in the cylinder. This is done using a special stopper and clamp, but you can use the usual rope. Rotating the clutch, it is necessary to identify the moment when the piston reaches the outlet. The rope lowers into the candle hole and secures the piston. For convenience, several knots are tied on a rope. After replacing, the rope will need to be removed, so you should not let it out.
  4. After this, you can proceed to unscrew the clutch nut. It is important not to forget that there is a left-hand thread, that is, you need to twist in a clockwise direction. The use of a chisel with a hammer is not acceptable. This will damage the nut.
  5. Now you can remove the clutch and the drive sprocket drum.
  6. Clutch drum replacement.
  7. Assembling all parts together in reverse order.

When replacing an asterisk, some features of various saws should be considered. For example, in a Stihl chainsaw, there may be a washer between the sprocket and the motor. It is necessary to remember its position, remove and repeat the position during assembly.

Also, some chainsaw oil drives are equipped with a mustache spring to transfer rotational energy from the sprocket to the pump. If, when assembling the saw, the mustache does not fall into its groove, the oil will cease to fall onto the saw chain, which can lead to sad consequences.

To avoid most breakdowns, including the drive sprocket, it is necessary to monitor the technical condition of the saw, regularly inspect, lubricate, etc. It is also necessary to ensure that nails, concrete, stone and other obstacles that lead to soon wear of parts do not meet on the path of the chain.

As for the replacement of the drive sprocket, here you should use information about the design features of the saw (Husqvarna, Stihl, Ural, Friendship and others), which can be found in the instructions that came with the saw.