The main reasons for replacing the drive sprocket
The universal wrench is the main tool that will be required when replacing the sprocket.
Chainsaw Repair. Replacing the Drum and Sprocket (Poulan Part # 545171901)
The most common reasons that force the tool to be repaired associated with the replacement of the drive sprocket are:
- jamming of the chain due to the occurrence of defects during the operation of the unit;
- high wear of the sprocket as a result of long-term operation of the unit.
With regular use of the device, increased wear of the drive sprocket occurs as a result of the application of increased loads on it in the process of sawing wood. There are two ways to operate the device:
- using one saw chain;
- using several saw chains alternately.
When using the first method of operation, the chain is operated until it is completely worn out. This method has several disadvantages. The main one is the problem of monitoring wear 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 sprocket, which allows you to extend the period of operation of the device before repairing the sprocket. In addition to the wear of the sprocket, one should not forget about the bearing that is installed in the sprocket. This structural element works at any engine speed. When replacing the sprocket, change the bearing at the same time.
The clutch complete with the sprocket must be replaced in a timely manner. If the repair work is not carried out on time during the operation, the tool experiences increased vibration, which leads to an increase in the wear of the 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 life of the sprocket is twice that of a single chain, so two chains should be used during operation. After the chains have reached the end of their life, replace the chains and the drive sprocket at the same time.
How to remove a drive sprocket from a chainsaw?
As already noted, the sprocket can have a split and pressed-on crown. Therefore, the sequence of actions will be different.
For a stationary positioned crown, the following are sequentially produced:
- Dismantling the casing;
- Removing the bar along with the chain;
- Disconnecting the clutch from the engine (the piston must first be locked);
- Removing the clutch together with the drum;
- Removing the crown from the drum using a conventional open-end wrench (some manufacturers also attach a puller to the spare parts kit).
The assembly of the assembly is carried out in the reverse order. For some models, before dismantling the crown, you will also have to remove the air filter.
When disassembling the drive sprocket for a chainsaw, which has a replaceable crown, the order of work will be almost the same, but at the final stage only the crown needs to be replaced.
After completing the work, it is necessary to check the effectiveness of the replacement. To do this, check the chain tension: if, when the brake is released and you try to pull the chain in the direction of its movement, it is motionless, then the fastener is “overtightened” and the tensioner should be slightly released.
The success of the work is determined by the availability of a special repair kit purchased for a specific brand of chainsaw. To move the carburetor away from now you need to remove the STIHL 180 chainsaws, like. Otherwise, you should know exactly the size of the saw and the pitch of the teeth.
Features of the clutch drum in chainsaws
The drum located at the base of the clutch of the 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 drive sprocket also needs to be replaced regularly. If we talk about household tools, then everything here depends on the amount of work performed and the load that is on the circuit of the device.
Most often, the sprocket, ring and saw bearing need to be replaced.
In any case, the main reason for replacing a sprocket is chain wear on its teeth. In the case when a monolithic drum is installed in the device, the surface of the chain cuts 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 only to replacing the crown.
Usually, in order to remove the sprocket from the 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 activity does not look complicated, but it requires you to have all the necessary parts and tools. The sprocket replacement process is the same for any device model.
Changing drive sprocket Echo CS280WES
Chainsaw drive sprocket device
An asterisk or centrifugal mechanism is a part shaped like a star. It absorbs the engine torque and transfers it to the guide and saw chain. This guarantees the rotation of the cutting attachment and the sawing process itself. It works in automatic mode, which depends on the magnitude of the motor speed.
The clutch drum can be located both outside the chainsaw, and on its inside. under a separate cover. It provides a protective function not only for 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 the chain rotation, the drive sprocket of the saw prevents the occurrence of malfunctions of the motor system in cases where the chain jams or stops rotating.
Design features of leading sprockets
The pitch of the teeth of the drive gear is one of the main parameters of the assembly. It must match the pitch of the chain links and, just as important, the pitch of the teeth of the driven sprocket located at the end of the chainsaw bar.
According to their design features, the drive gears are divided into:
Experts identify the following signs of wear on the drive gear teeth:
- semicircular depressions are visible at the base of the tooth;
- the thickness of the prong changes with height;
- chipped areas at the summit;
- scratches appeared inside the hub hole;
- the chain has rubbed the groove on the sprocket;
- when starting the chainsaw wedges.
A chainsaw sprocket with such signs should not be used, 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 is necessarily checked, whether it is securely fixed. If the screw regulating the position of the chain roller and its tension is loosened, or the nuts securing the bar to the body are loosened, it deviates from the plane of the chain. In this case, the blade rollers 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 replaceable and stationary crown
After tightening the fasteners and adjustments, a test run is made. If 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 pull off the retaining ring with a screwdriver, after which the sprocket can be easily removed.
In the second case, you will first have to remove the clutch. To do this, you need to lock the shaft on which it is located. This can be done in two ways:
- Or, unscrew the candle and screw in a special piston stopper instead, which would prevent the movement of the latter.
- Alternatively, 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 in that the sprocket is often tightened quite tightly, which is why 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 folk method from the next paragraph.
- The popular way is that instead of a special stopper, you can push a piece of cloth into the combustion chamber through the hole where the candle is wrapped, leaving part of it outside so that you can then pull it out. The fabric will take up all the space inside and prevent the piston from moving upward, which will cause the shaft to stall. At the same time, 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, the clutch can be unscrewed. You need to use either a special puller, or you can do with a suitable open-end wrench by inserting it into the grooves on the clutch. Unscrewing is performed clockwise, since the thread on the shaft is left.
By unscrewing the clutch, you can now easily remove the sprocket.
When changing a star, it is also necessary to change the bearing located under it. They are usually sold in one repair kit.
The installation of new parts must be done in the reverse order.
How to change the gas chainsaw clutch and drive sprocket
As you can see, nothing complicated. everyone can handle it.
Chainsaw drive sprocket classification
In accordance with the power class of the saws on which they are installed, the asterisk can be:
- professional;
- household.
The main difference between them is the frequency of replacement and the rate of wear: in models of the “Profi” series, wear is faster, and repairs are more frequent.
By design features, the leading chainsaw sprockets are:
The latter consist of a hub with a stationary rim of a certain number of teeth. Their factory pressing does not allow removing the crown separately from the hub. This situation is typical for many Chinese chainsaws, for example, from the “Champion” brand.
The case with prefabricated sprockets is simpler: the removable crown is quickly unscrewed from the drum axis, so the repair does not cause any particular difficulties. This option is the advantage of most European saws, such as STIHL or Husqvarna.