Husqvarna 455 Chainsaw sprocket repair
Replacing a worn chain saw sprocket
Also, the owner of a chainsaw may encounter such a nuance: on Chinese imported chainsaws or electric saws, the sprocket on the clutch mechanism may be located in an unusual way. On older models, when the chain teeth are worn out, you need to unscrew and change the drum, one-piece with a drive. On newer models, you can replace the sprocket separately.
Algorithm for self-replacement of the clutch drum with an asterisk
How is the replacement of the leading sprocket on an electric saw or chainsaw performed. more on this in detail.
For the procedure for replacing an asterisk, you need to do the following:
- remove the chain brake cover and pull it towards you (avoid contact of the brake band with the clutch parts);
- using a wrench, loosen the nuts holding the chain tension and the chainsaw cover;
- remove the chain and then the bar, removing debris and sawdust from the holes for the fasteners;
- we fix the piston in the cylinder using a regular cord, but if possible, you need to use a piston stopper or a special lock;
- the clutch begins to rotate and do this until the piston touches the outlet;
- after which the stopper or lace is lowered into the candle opening and fixed there, tying several knots (the stopper will fix itself);
- unscrew the clutch nut (note. the thread of this nut is left-hand, take this into account when unscrewing);
- it is forbidden to use hard tools so as not to break the soft metal of the clutch nut;
- then the clutch is removed;
- after removing the sprocket gear itself;
- replace the old asterisk with a new one;
- in reverse order to assemble the structure.
The main signs that the asterisk needs to be changed:
- the chain has been replaced twice on your chainsaw (one of the current rules for operating a chainsaw and an electric saw. with frequent and active use of the tool, after two chain changes, the drive sprocket should be replaced);
- the quality of sawing has worsened, the chain needs to be tightened more often;
- you installed a new chain, which does not fit the old drive sprocket (this part is not universal, and also has its own pitch, in addition, the steps of the drive and driven chain sprockets must match, otherwise the tool will not work);
- you are using a different bus, shorter or longer.
What tools are needed to replace the sprocket
To replace the drive (drive) sprocket, you will need the following tools and accessories:
- a special key for removing this part (usually supplied with expensive branded chainsaws, cheap saws are not equipped with such a key);
- a punch made of aluminum or copper (only from soft metals and only in the absence of a key);
- hammer (for striking the punch while unscrewing the sprocket);
- flat screwdriver for tightening the nut;
- sprocket bearing grease.
Why you need to replace the asterisk?
You need to remove a worn sprocket for the following reasons:
- with an old sprocket, the saw chain will stretch very quickly. after a few uses, the chain will hang, and tension will not help;
- if you put a new chain on an old sprocket, the smoothness of the chain will decrease, the quality of the cut will deteriorate, the chain will lead to the side when cutting;
- the general wear of the chainsaw will accelerate, the tool can fail at any time;
- an open circuit may occur or the chain will jam during operation (it is dangerous with hand injuries and damage to the case of an electric saw, chainsaw);
- the tire will heat up faster, which will lead to rapid overheating of the chainsaw;
- the load on the engine and the body will increase.
Important! Do not change at your own discretion the dimensions of the sprockets during repair, use the manufacturer’s standard. Unauthorized replacement will lead to a deterioration in the technical performance of the chainsaw or electric saw.
Restoration or replacement?
Drive parts are manufactured from extra strong high alloy alloys in an industrial environment. In addition, they are subjected to special treatments to improve their strength properties, wear resistance and corrosion resistance. These may include:
- Hardening.
- Vacation.
- Shot-blasted surface sealing.
- Protective coating.
It is impossible to repeat such a technological process in a home workshop. An attempt to restore by surfacing with subsequent milling to size will also not work. Such a restored gear will work several times less than the factory one. The cost of a repair kit is incomparably small compared to the wasted effort and time.
Replacing a part in service workshops is not cheap, so the most reasonable and economical is to replace it yourself with a suitable industrial gear.
Feasibility of timely replacement of worn out parts of the chain drive
The design of its crown determines such an important parameter as the choice of the chain in step.
- Installing a new part on a worn sprocket reduces the smoothness of its movement, accelerates wear, initiates the risks of its breakage and creating a traumatic situation.
- There is also an increase in operating loads on the engine and the elements of the kinematics of the tool.
- A similar process takes place when old stretched chains are installed on the tire, the diameter of which is adjusted to the size of the tire by removing some of the links.
Experts also advise against arbitrarily changing the size of the sprockets. The experiment can negatively affect the engine life and the kinematics of the tool as a whole.
The safety of sawing work of various degrees of complexity is ensured by the effective operation of the emergency stop brake and devices that block the expansion of the chain ends in case of accidental breakage. In any case. the most reliable prevention of emergency situations, maintenance of the chainsaw in good technical condition.
How to extend the life of a leading sprocket?
Experienced sawers recommend working with several of the same blades, changing them as the links become dull. This technique will help to significantly reduce wear on the drive gear, but certainly cannot completely prevent it. Sooner or later it will have to be removed and replaced.
How to unscrew the drive sprocket on a chainsaw
Many owners of gasoline chainsaws after a device breakdown are worried about how to remove a chainsaw sprocket.
When replacing the sprocket, all work must be carried out carefully and with care.
The design of the chainsaw device is a classic mechanism that is driven by an internal combustion engine. The design of the unit uses one of the simplest single-cylinder two-stroke carburetor engines that run on gasoline. The simplicity of the engine and the design of the chainsaw as a whole is the key to the trouble-free and reliable operation of the device in harsh operating conditions. Chainsaw operation does not require a large amount of knowledge and skills from the operator. The only condition for long-term and trouble-free use of the device is the implementation of regular technical inspection and maintenance of the device. In the process of working with the device, it is required to regularly replace the wearing parts. To reduce tool wear, control the lubrication quality of the saw chain, its tension, the degree of chain wear and the degree of wear of the drive sprocket.
Before repairing a chainsaw, you should study its design. To replace one of the main structural elements of the device. the drive sprocket. it is required to study the mechanism of the clutch of the unit.
Replacing worn parts
If the gear has a replaceable rim, the condition of the base should be carefully checked. If nicks, chips, deep scratches, changes in geometry or corrosion are found, not only the crown, but also the entire part should be replaced. Working together in one unit of worn and new parts will reduce the life of the entire unit. The risk of seizure or chain breakage increases significantly.
In addition, the vibration load on the clutch, transmission and engine of the device will increase. The same factors arise during long-term operation of one chain.
Folk “craftsmen” sometimes reanimate a stretched canvas chain, simply throwing out one or for a link and re-pressing the axles. In this case, the chainsaw requires replacement of the sprocket.
Also, you should not change the diameter of the gears (and, accordingly, the number of teeth). When working with an enlarged or reduced sprocket, forces arise in the transmission and engine that the designers of the device did not count on. This will shorten the tool life and not increase its productivity.
Despite the presence of safety systems in the construction of the chainsaw, which instantly stop the movement of the blade when it breaks or breaks the tire and protects from the scattering of the torn links, it is better not to bring such situations to such situations. The need to replace the gear is only intensified by safety requirements.
Unit clutch design
Chainsaws are units that are equipped with drive sprockets, which are a single complex with a clutch basket.
The clutch engages automatically, depending on the number of engine revolutions.
A centrifugal clutch is installed on the units, which works in automatic mode, depending on the number of engine revolutions.
When the engine of the unit is idling or at low speeds, the elements of the clutch basket, which have friction linings, have a certain level of freedom in the radial direction. The presence of freedom of movement leads to the fact that, under the action of the springs, the elements are attracted to the center of the rotation shaft and do not transfer the rotational motion to the sprocket drum. With an increase in the engine speed of the apparatus, the centrifugal force exceeds the force of the springs, which leads to the displacement of elements with friction linings. These elements are pressed against the inner walls of the drum under the action of centrifugal force. Due to this contact, the rotational movement is transmitted to the drum and the sprocket, which drives the saw chain of the tool. The chain saw sprocket can be located either outside the tool, or under a special cover that protects the mechanism from damage, and the operator of the device from injury.
The main advantage of this type of clutch is that when the saw chain is jammed, elements with friction linings slip, which protects the internal combustion engine from serious damage.
How to remove a drive sprocket from a chainsaw
depending on the design features of the gear, the sequence of operations required to remove it also differs.
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.
Alternative solutions
The drive designs for most chainsaws presented in the domestic and semi-professional market segments are fundamentally similar. The sequence of operations required to remove and replace the drive gear is also the same.
As already mentioned, the best option would be to purchase a regular repair kit for this model.
The advantage will be the presence of a bearing in the kit. You should also check the presence of a drum puller designed for this saw, as well as a retainer to secure the piston in a certain position.
If, nevertheless, a brilliant idea of ”improvement” or modernization of this unit of the chainsaw arises, then it is better to consult with specialists and simply with experienced people.
Replacing worn parts
If the gear has a replaceable rim, the condition of the base should be carefully checked. If nicks, chips, deep scratches, changes in geometry or corrosion are found, not only the crown, but also the entire part should be replaced. Working together in one unit of worn and new parts will reduce the life of the entire unit. The risk of seizure or chain breakage increases significantly.
In addition, the vibration load on the clutch, transmission and engine of the device will increase. The same factors arise during long-term operation of one chain.
Folk “craftsmen” sometimes reanimate a stretched canvas chain, simply throwing out one or for a link and re-pressing the axles. In this case, the chainsaw requires replacement of the sprocket.
Also, you should not change the diameter of the gears (and, accordingly, the number of teeth). When working with an enlarged or reduced sprocket, forces arise in the transmission and engine that the designers of the device did not count on. This will shorten the tool life and not increase its productivity.
Despite the presence of safety systems in the construction of the chainsaw, which instantly stop the movement of the blade when it breaks or breaks the tire and protects from the scattering of the torn links, it is better not to bring such situations to such situations. The need to replace the gear is only intensified by safety requirements.
How to extend the life of a leading sprocket?
Experienced sawers recommend working with several of the same blades, changing them as the links become dull. This technique will help to significantly reduce wear on the drive gear, but certainly cannot completely prevent it. Sooner or later it will have to be removed and replaced.
When and why do I need to replace a worn chainsaw sprocket
The drive sprocket of a chain saw or electric saw is one of the most important parts of a saw. The main function of the chainsaw sprocket is to transfer engine torque to the saw chain. This transmission is carried out via a centrifugal clutch. By type, sprockets can be divided into professional and household, as well as chains. During the operation of the chainsaw and sawing wood, the drive sprocket, like the chain, gradually wears out.
Let’s find out in more detail why it is necessary to replace a worn chain sprocket or an electric saw and when it is better to perform such a replacement.
Structural problems, differences between different models
Branded chainsaws have a special design that does not allow replacing a worn drive without dismantling the clutch and other parts of the chainsaw. That is, the saw needs to be almost completely disassembled. modern models of expensive chainsaws are always equipped with a special key.
Also, the owner of a chainsaw may encounter such a nuance: on Chinese imported chainsaws or electric saws, the sprocket on the clutch mechanism may be located in an unusual way. On older models, when the chain teeth are worn out, you need to unscrew and change the drum, one-piece with a drive. On newer models, you can replace the sprocket separately.
The sequence of repair work
At the first stage, the saw headset is dismantled, the guide bar cover is removed. After removing the cover, the guide bar and saw chain are dismantled. The fastening nuts are unscrewed using the universal wrench, which is included in the delivery set of the unit.
DIY How To Remove Chainsaw Clutch without Specialty Tools. Saw Repair. Poulan Husqvarna Stihl Echo
After removing the saw chain and guide bar, the air filter is removed. Then the spark plug is removed. In place of the dismantled spark plug, a pre-prepared engine piston stopper is installed. The stopper allows you to fix the position of the piston in the cylinder and prevent the crankshaft from turning. The clutch should be removed using a special puller installed in the socket of the universal wrench. All actions should be carried out clockwise.
After removing the clutch, an approach to the internal parts of the device opens, that is, after removing the clutch, the sprocket can be removed.
After removing the clutch drum, depending on its type, the crown and sprocket are inspected and checked. Depending on the design of this unit, the worn out structural elements are replaced. When carrying out repairs, special attention should be paid to the springs of the centrifugal mechanism and its cams. If wear is found, replace them.
If the components do not cause any complaints, all structural elements are installed on the chainsaw in the reverse order. First of all, unscrew the piston stopper and pull out the starter cord, after which the piston stopper is installed in place. This complex sequence of operations makes it possible to clamp the centrifugal mechanism onto the crankshaft of the unit. The clutch is installed in place and clamped using the universal wrench supplied with the chainsaw. Clamping with a key should be done counterclockwise.
The last stage of the repair work is the installation of the remaining structural elements of the device.
When replacing the sprocket, all work must be carried out carefully and with care. All repair work must be carried out using special tools, otherwise the centrifugal mechanism or the saw chain may be damaged.
The main reasons for replacing the drive sprocket
The universal wrench is the main tool that will be required when replacing the sprocket.
How to replace chainsaw drive sprocket/rim sprocket Husqvarna 359
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.
What tools are needed to replace the sprocket
To replace the drive (drive) sprocket, you will need the following tools and accessories:
- a special key for removing this part (usually supplied with expensive branded chainsaws, cheap saws are not equipped with such a key);
- a punch made of aluminum or copper (only from soft metals and only in the absence of a key);
- hammer (for striking the punch while unscrewing the sprocket);
- flat screwdriver for tightening the nut;
- sprocket bearing grease.