Sprocket for the Chinese chainsaw
A stable and continuous transmission of the engine’s power to the chain saw’s cutting units depends on a small sprocket that plays an important role in the chain saw’s clutch system. It works in a constant state of friction and heats up quickly. This leads to deformation, cracks and other signs of a worn sprocket over time. As soon as any defect is detected by the operator, the part will need to be replaced.
In shape and appearance, the chain saw clutch sprocket does resemble a star. The main function of this compact component is to receive, store and transmit power immediately from the engine running to the integrated cutting elements of the chain saw in use. That’s how a chainsaw drive sprocket keeps the chain saw’s gears working continuously and ensures that the chainsaw is effective for a variety of tasks on the lot. A second important function of the sprocket is to protect the engine in the event of a chain sticking or an emergency stop.
The sprocket and the drum it contacts can be located on the inside or outside of the chainsaw body. In the first case, it is reliably protected from damage, but the second arrangement makes it easier to service and replace the part.
Depending on the chainsaw manufacturer and its purpose, the sprocket in its clutch can be made of metal or plastic. The second option is common among the Chinese brands that produce mostly cheap household chainsaws. Metal sprockets are much more reliable and are installed on brand equipment for professional use.
Types of drive sprockets of modern chainsaws
Depending on the technological arrangement of the sprockets, they can be:
- one-piece. elements of this type structurally consist of a regular hub, equipped with a stationary ring with a specific number of teeth. In the factory, both parts of the sprocket are pressed into each other, so it cannot be dismantled. Most of Champion brand chainsaws and other brands of garden equipment from China are equipped with solid chain sprockets;
- assembly-type parts of this type have a detachable ring gear that allows you to quickly separate it from the hub. It makes clutch repair more convenient and cheaper. STIHL and Husqvarna chainsaws are most often equipped with collapsible sprockets.
The type of design of the chainsaw clutch sprocket plays an important role when choosing a chain saw. If the saw will be used by a novice gardener, it is better for him to choose a model with a solid sprocket. If the user already has experience in maintaining and repairing a chainsaw, the tool equipped with a collapsible sprocket will be more suitable for him.
When to change chainsaw sprocket?
About the urgent need for a sprocket replacement on a chainsaw. The operator of a chain garden tool may be prompted by the following signs:
- Unstable cutting chain rotation. the cutting attachment can rotate at varying speeds, some faster, some slower. In this case the operator himself does not make any actions with the gas pedal;
- Noise when the chain is turning. it can come from the chainring or from the clutch itself. In addition, the sounds can come not only from the chain passing a certain section of the bar, but also in different positions on the guide rail;
- crooked saw trimmer chainring. while working with wood, the chain on the bar of the chain saw can arbitrarily change its position on the trunk. it can move sideways from the original axis by a distance of 0.2-20 mm;
- blue or red spots on the guide rail. if you can see some color on the guide rail when you are sawing wood, it means that it has been overheating regularly. In this case the clutch sprocket will need to be replaced urgently.
Another reason to change a sprocket is sprocket wear. Uneven tooth length and spacing can tell the operator that the teeth are worn out. To notice a defective part, you will need to disassemble the clutch from time to time for routine inspection and cleaning.
Drive sprockets for chainsaws, their types and design
There are two types of chainsaw sprockets. prefabricated and one-piece. The one-piece is a monolithic element that is installed behind the clutch. the so-called fixed sprocket. The chainring is fixed to the clutch drum, connected to the centrifugal clutch.
A similar design is used in most chainsaws, including those made in China. It’s no big deal how to remove the chainring from a chainsaw, but you have to remove the whole chainring.
The situation is even simpler with more expensive models. Their chainsaw sprockets have a prefabricated design with a removable ring. The sprocket is put on the drum shaft and transmits torque to the chain. So it’s really easy and fast to change the sprocket on your chainsaw. the gear rim comes off and the drum can stay in place.
When to change a chainsaw sprocket: types of faults
The main problem with drive sprockets is tooth wear. In normal use, a chainsaw drive sprocket will have very little wear. if the chain is used properly and is properly lubricated. But if during cutting the blade will bump into a hard object (a rock, a nail, etc.), it will be difficult for the trimmer to stop.e), the tooth that was moving the chain at that moment will receive a very high dynamic shock. So bad that the sprocket can easily break. This causes the chain to slip during use and can slip off the bar. causing injury or damage to other parts.
In spite of the constant lubrication of the web, the chain moving at high speed has an abrasive effect on the sprocket. That’s why it will wear out over time anyway. to know when the sprocket on a chainsaw bar needs to be replaced, do a regular inspection of the assembly.
Bearing failure is unlikely if operated correctly. If it’s lubricated in time and well maintained, the sprocket will wear out much faster than the bearing. Nevertheless, if it happened, it is necessary to unscrew the sprocket on the chainsaw, replace the bearing, pre-lubricate it well, and then install it back.
When to change a chainsaw chainring: what kind of failure?
The main problem with drive sprockets is tooth wear. In normal use, a chainsaw drive sprocket will have very little wear. if the chain is used properly and is properly lubricated. But if the saw blade encounters a hard object (stone, nail, etc.) while you are sawing, the chain could slip.e), the tooth that is moving the chain at that moment will receive a very strong dynamic shock. So hard that the sprocket can easily break. As a result, the chain will slip during work and can come off the bar. causing injury or damage to other elements.
Despite the constant lubrication of the bar, the chain moves at high speed and still has an abrasive effect on the sprocket. That’s why it will wear out over time anyway. check the chain saw chainwheel regularly to see when the chainwheel bar needs replacing.
Bearing failure is unlikely if operated correctly. If it is timely and well lubricated, the sprocket will wear out much faster than the bearing. Nevertheless, if it happened, it is necessary to unscrew the sprocket on the chainsaw, replace the bearing, pre-lubricating it well, and then install it back.
How to remove the sprocket from a chainsaw
The first and most important advice. if you do not know how to remove the sprocket on a chainsaw, it is better to go to the service. In the case if you understand the technique, you can do it yourself, especially if you need to do it in the field or to make repairs as quickly as possible. Let’s look at both versions: with a replaceable and a stationary sprocket
The variant with a fixed sprocket
The procedure for how to remove the drive sprocket from a chainsaw may vary slightly depending on the model, but in general it is the following:
- Use a wrench to unscrew the tire cap fasteners.
- Loosen the chain tensioner, then remove the chain itself and the bar, freeing the chainsaw sprocket.
- Remove the air filter. It is not necessary for all models, but in about 80% of the cases it is obligatory.
- The piston must be accessible. To do this, unscrew the spark plug.
- It is necessary to lift the piston to the uppermost point. it is necessary to do it manually, quietly rotating the star on a chainsaw.
- When the piston is up, lock it in place. You need a piston stopper for this, or if you don’t have one, a soft rope. It is tamped as tightly as possible in the channel to block the stroke of the piston.
- To remove the sprocket, use a clutch puller or an ordinary open-end wrench, but only if the design allows it. Do not use the chisel and hammer that many people are accustomed to.
- Unscrew the clutch clockwise.
- The drive sprocket on the chainsaw is replaced with a new one.
The assembly is carried out in the reverse order and the screwing in of the coupling is counter clockwise.
This is the general order of how to remove the sprocket from a chainsaw of Chinese or any other manufacture in the variant with a stationary sprocket.
A variant with a removable ring gear
In this case the whole procedure is similar to the method described above, with the only exception. if the teeth on the ring gear fail, only the ring gear is replaced. But the sprocket still has to be removed, because the chain saw.к. Otherwise it will be impossible to get access to it.
Types of stars
Depending on chainsaw class, all sprockets are divided into two groups: professional and consumer sprockets. The first type of parts have increased wear resistance, are made of durable metal alloys, not subject to corrosion and mechanical damage. Household chainsaws more often require replacement and scheduled repair, and if the tool is used frequently, diagnostics is recommended every six months. The following types of sprockets can be distinguished by design features:
- Fabricated. The removable ring gear is easy to unscrew from the drum axle, making it easy to check and replace this part. Almost all chainsaw models in Europe have it.
- One-piece. They consist of a hub and a stationary ring (the number of teeth may vary, you need to read the chainsaw manual carefully). Because of the factory press fit, the crown cannot be removed separately from the hub, so if it fails, the entire clutch drum must be disassembled. This mechanism is usually found on Chinese models.
If you plan to service your chainsaw yourself, it is recommended that you purchase a tool with a professional type of drive sprocket. It should be demountable, which makes repair and maintenance of the tool cheaper.
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Chainsaw drive sprocket design
A chainsaw has not only a drive sprocket, but also a driven sprocket. The chainsaw’s drive sprocket is in the tool’s structure, and the idler sprocket is at the end of the bar. The purpose of the slave unit is to equalize the tension and direction of movement of the chain drive.
Drive units come in one piece and assembled units. One-piece products consist of a hub with a pressed-on sprocket. When replacing, the entire mechanism is removed because the toothed structure is one-piece. Many well-known brands of chainsaws are equipped with one-piece gears from the factory.
What a solid gear looks like on a chainsaw
One-piece products are more advanced, because their replacement is simplified by the simplicity of the mechanism design. Only one pinion gear is replaced, the cost of which is half as much as the assembled mechanism. The following signs can be used to determine the appropriate wear on the gear teeth:
- Large radii in the tooth transitions
- Uneven tooth width
- Detection of chips and metal shavings on the top of the teeth
- Scoring and risks on the inside surface of the hub holes
- When the tool is started, the chain is found to be jammed
If the drive unit is worn, it is essential that it be replaced. This can be done by yourself by first disassembling the tool and determining the version of the device that has been installed. If even the tool has a non-disassembled pinion, it is possible to install a prefabricated mechanism instead, which is more rational.
There are two varieties of installation of drive stars on chainsaws. The first method involves the location of the pinion from the outside. These designs are the most common on STIHL chain saws. The design of such a device is shown in the photo below.
Non-disassembled type product on the tool
The second variant is common to tools of Chinese origin. Gear teeth are not located on the outer side, but on the inner side, i.e. the device is positioned backwards.
Star design on a Chinese chainsaw
Depending on the design of the tool, the process of dismantling the products in question will differ.
This is interesting! To prolong the life of the chainsaw drive sprocket, it is necessary to run in the tool, and at work not to overload it, which depends on the purpose (domestic, semi-professional or professional). With a domestic tool it is possible to cut a tree, but the saw is not meant for it, and frequent use with overloading will lead to component parts deterioration.
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Main sprocket replacement on Husqvarna 154, 254, 262 chain saws
For chain saw models Husqvarna 154th, 254th, 262th series
, Equipped with a 0.325 pitch 8-tooth chain, the Rezer SP 38071 drive sprocket is used. The part differs from the previous one in its metal construction. That means there is no such thing as a removable ring.
On the one hand such part loses
in service life. on the other hand has a more attractive price. Cost is about half as much as a cogwheel replacement sprocket. You can buy sprockets for the Hugen 154, 254, 262 models by clicking on the following link.
How to replace the drive sprocket on the Husqvarna 154, 254, 262
has a slightly different algorithm. Let’s take a closer look at it.
Remove the chainsaw sidewall to get access to the saw group
.
Using a combination wrench
Loosen the clutch and remove it together with the stitching.
Remove the cable starter
on the opposite side. Use Allen keys.
Secure the shaft at the impeller side with a 13 mm open-end wrench
.
Using a special wrench
Remove the clutch clutch. Unscrewing should be clockwise.
Reassemble in reverse order
Tighten the clutch clutch in an anticlockwise direction. The force must not be too great. because the clutch is self-tightening during rotation.
In fact, the replacement process is not very complicated
and it’s quite possible to do it yourself. You can buy quality sprockets for Husqvarna 154, 254, 262 in our TUKINGARDEN store.
Use of puller
A special tool that is designed to dismantle parts that are difficult to remove is called a puller. It’s pretty self-explanatory. In our case to remove the crank arm from the bicycle’s carriage shaft. It looks like this. This kind of connecting rod puller provides the ability to remove the pedal as well.
The connecting rod is held on the shaft by a heavy-duty 8 mm head bolt. It is very easy to unscrew the bolt. The trick is that the rod sits on the shaft with a small amount of tension and has a tapered fit. It is very common in wet weather for water and mud to get into the connecting rod/shaft junction. Then it gets stuck to the shaft and it’s almost impossible to remove the connecting rod. But of course we have a crank pin puller in our toolbox, which is a complex lathe part. a screw with a two-level head for a socket wrench and a socket. Screw has a cunning nut with male and female thread. It’s a long explanation, but the picture is very clear.
Are there ways to extend the life of an existing sprocket??
Basic ways to extend the service life of a chainsaw drive sprocket:
- use more than one chain (preferably three). This method is the gentlest and most convenient for the chainsaw owner because it’s not necessary to constantly tighten the chain that has been worn out by intensive work. Operating three chains alternately will preserve sprocket life and delay replacement;
- good maintenance of the drive sprocket bearing. This part plays an important role in the functioning of both the drive sprocket and the engine. For lubrication, it is recommended to use a special lubricant. The sprocket bearing is not engaged all the time, but only at idle speed, so it needs periodic lubrication. You can use a bar nose grease such as standard Repsol or Husqvarna grease.
Chainsaw Drive Sprocket Classification
According to the power class of the saws on which they are mounted, the sprocket can be:
The main difference between them is the frequency of replacement and the rate of wear: in the “Pro” series models, wear is faster and repairs are more frequent.
According to their design features, there are chainsaw drive sprockets:
The latter consist of a hub with a stationary crown of a certain number of teeth. Their factory press fit makes it impossible to remove the sprocket separately from the hub. This situation is typical for many Chinese chain saws, for example, from the brand “Champion”.
The case with prefabricated sprockets is easier: the removable ring is quickly enough unscrewed from the drum axle, so the repair does not cause much difficulty. This option is an advantage of most saws of European origin, for example, STIHL or Husqvarna.
How to classify chainsaw drive sprockets
According to the power class of the saws on which they are installed, the sprocket can be:
The main difference between them is the frequency of replacement and the rate of wear: in the “Pro” series models wear is faster, and repairs are more frequent.
There are chainsaw drive sprockets by design:
The latter consist of a hub with a stationary crown of a certain number of teeth. Their factory press-in makes it impossible to remove the crown separately from the hub. This situation is typical for many Chinese chainsaws, for example, from the brand “Champion”.
The case with prefabricated sprockets is easier: the removable ring gear is quickly enough unscrewed from the drum axle, so the repair does not cause much difficulty. This is an advantage of most European-made saws, for example, STIHL or Husqvarna.
What tools do you need for star replacement?
To replace the drive (drive) sprocket, you will need the following tools and accessories:
- a special wrench for removing this part (usually supplied with expensive brand-name chainsaws, cheap saws are not equipped with such a wrench);
- A punch made of aluminum or copper (only soft metals and only if a wrench is not available);
- a hammer (for hammering on the dowel while unscrewing the sprocket);
- A flathead screwdriver to tighten the nut;
- Lubricant for the sprocket bearing.
Alternative solutions
The sequence of operations is identical for almost all known models on the domestic chainsaw market. Experts recommend replacement with a brand-name part.
If it is a question of upgrading this node, the feasibility of such a change should be clarified by consulting an experienced professional.
Your best bet is to buy a repair kit that also includes a replacement bearing. In addition to a wrench, you may need a model-specific clutch drum puller, a metal or plastic stopper to hold the piston in position.
Clutch repair: the nuances of the process
When servicing clutches yourself, you need to know that:
- some saws have a washer between the sprocket and the clutch and between the sprocket and the motor. Keep this in mind when repairing;
- The special spring for the oil pump drive must not be damaged during disassembly and must be returned to its original position. Otherwise the chain will be underlubricated or will cease to lubricate at all.
If it has been repaired, the tool should be checked to make sure it has no tensioners, no grease on the chain and the motor is running properly (it should engage smoothly and run smoothly). Only then can it be put into service.