Expert advise: How to correctly remove the chain sprocket from a chainsaw?
Regardless of the class of chainsaw and its performance characteristics, the design of removable saw headsets is virtually identical. This chainsaw includes a guide bar made of a special alloy and a chain that is activated by the toothed rim of the drive unit. To extend the life of your chainsaw chain, it is important to change the sprocket on your chain saw in good time.
The design of its chainring determines the chain pitch.
- Installing a new part on a worn sprocket reduces the smoothness of its motion, increases wear, and causes risks of breaking the sprocket and creating an injury-prone situation.
- Operating loads on the motor and kinematic elements of the tool also increase.
- A similar process occurs when old sprocket chains are mounted on a tire, the diameter of which is adjusted to the tire size by removing a portion of the links.
It is also advised not to change sprocket dimensions arbitrarily. Experimentation can have a negative effect on engine life and overall tool kinematics.
Safety of sawing works of different degrees of complexity is secured by effective work of emergency stop brake and devices blocking chain ends spreading in case of accidental breakage. Either way. the most reliable way to prevent malfunctions and keep your chainsaw in good working order.
Criteria for your own choice of repair kit
Owners’ wish to equip their chainsaws with a chain of a different pitch would make them replace the sprocket with a part with a new chainringring profile. This requirement applies to the entire range of chainsaws made in Europe and China.
The operational reliability of a European-made chainsaw, when working under severe conditions of high loads, can be considerably impaired if a sprocket made in China is used instead of a brand-name sprocket.
It makes sense to replace worn drive chain parts in good time
The design of its ring gear defines such an important parameter as the choice of chain pitch.
- New parts on worn sprocket reduce smoothness of motion, force wear, initiate risk of chain breakage and dangerous situation.
- There is also an increase of operating loads on the motor and kinematic elements of the tool.
- The same process is followed when installing old chains on the bar, the diameter of which is adjusted to the size of the bar by removing part of the links.
Experts also do not advise to arbitrarily change the size of the sprockets. Experimentation can have a negative effect on engine life and kinematics of the tool as a whole.
Safe sawing jobs of different levels of complexity are ensured by an effective emergency stop brake and devices to block the chain ends in case of an accidental breakage. In any variant. the most reliable prevention of emergency situations, maintenance of chainsaw in serviceable technical condition.
How to extend service life of drive sprocket
In practice to provide even sprocket rim wear a set of several identical chains is used that are alternately changed as cutting edges of saw chain links dull. Nevertheless, sooner or later the user is faced with the need to replace a worn part.
The owner’s wish to have a chain of a different pitch leads to the necessity to change the sprocket for the part with a corresponding profile ring. This requirement applies to the entire range of chainsaws made in Europe and China.
Operational reliability of the European assembly saw, when working in difficult conditions of high loads, can significantly deteriorate, if instead of a branded part to put a sprocket of Chinese production.
Chainsaw clutch replacement. How-To’s and Videos
Faults in the chainsaw clutch. one of the most common failures of this equipment.
The question of how to remove the clutch on a chainsaw at home correctly and not to harm the tool, think not only inexperienced technicians, but also specialists who have repeatedly made its repair.
In cases where the petrol cutters start to turn on badly, stall instead of starting check the clutch for malfunctions is mandatory, and recommendations regarding what will be presented next.
Owners of chain saws probably wondered more than once. how to change clutch on a chain saw? On most chainsaw models the clutch can be easily removed and replaced manually by the owner, on few models unscrewing the drum can only be done in the workshop (for example, Husqvarna 137 or Partner 351).
In this review we will learn how to remove and change the clutch on your chainsaw yourself, when to do it and what tools you may need.
The chainsaw clutch drum is one of the most common consumables in a chainsaw, because it is the one that drives the cutting chain. The drums themselves are divided into two kinds. with a welded driving sprocket and with a replaceable ring, and in the second case only the replaceable ring wears out, the drum itself changes much less often.
When repairing the chainsaw clutch, stick to the rule. when two chains are completely worn out the tire is replaced, when two tires are worn out the clutch drum is replaced.
The level of wear of the sprocket can be determined without special tools, just inspect it. the chain, moving at high speed, eventually rubs the teeth on which it moves. If the wear is severe enough, replacement of the chainsaw clutch drum is inevitable.
In this article we will talk about Husqvarna 137 chain saw. Replacement of the clutch drum is an uncomplicated procedure and involves a few steps.
- First you need to remove the tire and chain brake cover. This is done with the combination wrench that came with the chain saw.
- Then remove the air filter cover, unscrew the spark plug, stop the piston of the Husqvarna 137 chain saw. For this procedure, it is recommended to use an ordinary rope, as there is a risk of puncturing the piston if a metal stopper is used.
- The clutch disc itself shows the direction to remove it and two holes for the clutch puller.
- Unscrew the clutch clockwise and remove it. A pressure washer is located under the clutch disc and must also be removed.
- Under the clutch drum itself there is an oil pump with a washer, on which the new drum is installed.
- Reassembling the chainsaw is done in reverse order except for tightening the clutch plate. After screwing the clutch onto the thread it is necessary to re-lock the piston to avoid deformation of the starter group which is on the other side of the crankshaft.
Chainsaw clutch drum replacement is an integral part of maintenance that will extend the life of all cutting equipment elements. Fitting a new cutting chain to a worn reel will cause the chain to stretch after only a few seconds of use.
In turn, this will result in a slight increase in chain pitch, increasing the load on the bearing and sprocket on the bar itself.
Therefore, having decided to save money on timely maintenance, be prepared for the fact that after a short period of time you will need a much more serious investment for the purchase of all consumable materials of the cutting equipment.
Chainsaw chain. saw chain marking and beginner’s guide to chain selection
When servicing clutches yourself, you need to know that:
- Several saws have a washer that is both between the sprocket and clutch and the sprocket and motor. Keep this in mind when repairing it;
- 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 not receive enough lubrication or will cease to lubricate at all.
The tool that had been repaired should be checked for the reliability of the bolt joints, lubrication of the chain and the serviceability of the motor (it should switch on smoothly and work smoothly). Only then can it be operated.
Chainsaw clutch repair with your own hands is carried out only in special protective clothing: mask and goggles.
The main malfunctions, their causes and methods of elimination:
- If the chain mechanism constantly rotates with unstable operation of the power unit. If the slack in the hitch is due to a defective spring, it can be the cause. In this case it is recommended to replace the damaged hitch with a new one.
- Extraneous noises are heard while the chain is moving. This problem may be caused by overheated cam or broken spring. The system should be inspected externally and any worn components replaced.
- If the breakdown is due to the fact that the clutch often slips, you need to replace the mechanism completely.
In addition to the basic rules of work described in the previous section, it is worth remembering about some nuances when replacing the clutch. Use only original manufacturer’s parts. this is a guarantee of long and productive work of the tool. The clutch thread on all chainsaws of any manufacturer is always left-handed. Before removing the clutch, carefully remove all dirt and dust from the tool to keep it from getting inside.
How to disassemble the clutch?
The illustration shows a simple chainsaw model with the main parts and assemblies.
To perform the disassembly of the clutch, you need to act according to the following plan:
- Remove the saw headset;
- Remove the chain and bar;
- Unscrew the cover of the air filter and carefully remove the plugs;
- Put the piston stopper in place;
- Remove the clutch with a puller;
- Unscrew the coupling clockwise;
- Remove the drum and put a new one in.
Assembly is performed in reverse order.
Types of stars
Depending on the class of chainsaw, all sprockets are divided into two groups. professional and domestic. The first type of parts have an increased wear resistance, made of durable metal alloys, not subject to corrosion and mechanical damage. Household sprockets more often require replacement and scheduled repairs, with active use of the tool, diagnosis is recommended every six months. The following types of sprockets can be distinguished by their design features:
- Assembled. The detachable sprocket can easily be unscrewed from the drum axle, making it easy to check and replace. Almost all chainsaw models in Europe have them.
- Solid. They consist of a hub and a stationary ring (the number of teeth may vary, you need to read the chainsaw manual carefully). Because it is pressed in at the factory, the pinion cannot be separated from the hub and therefore must be removed from the clutch drum if it fails. Such mechanism is often found on Chinese models.
If you plan to service your chainsaw yourself, it is recommended to buy a tool with a professional type of drive sprocket. It should be collapsible, which reduces the cost of repair and maintenance of the tool.
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Chainsaw sprocket design
A chainsaw has not only a drive sprocket, but also a driven sprocket. The chainsaw drive sprocket is in the structure of the tool and the driven sprocket is on the end of the bar. The purpose of the idler is to equalize the tension and direction of movement of the chain drive.
Gears can be solid and assembled. Solid pieces consist of a hub with a pressed-on ring gear. When replacing the pinion, the entire mechanism is removed, since the toothed structure is inseparable. Chain saws of many well-known brands 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 the replacement process is simplified by the simple design of the mechanism. Only one pinion is replaced, the cost of which is half as much as a prefabricated mechanism. You can determine the appropriate wear on the gears by the following signs:
- Large radii at tooth junction points
- Uneven tooth width
- Chipping and shaving of metal on top of the teeth
- Scoring and risks on the inner surface of the holes in the hub
- Chain jamming is detected when starting the tool
If the drive unit is worn, it is imperative that it be replaced. You can do it yourself, for which you first disassemble the tool, and determine the variant of the installed device. If even the tool has a non-disassembled pinion installed, it is possible to install a prefabricated mechanism instead, which is more rational.
There are two types of installation of drive stars on chainsaws. The first method involves the location of the gear on the outside. This design is the most common on STIHL chain saws. The design of such a device is shown in the photo below.
The product of the non-disassembled type on the tool
The second variant is characteristic for tools of Chinese origin. The gear teeth are not on the outer side, but on the inner side, i.e. the device is placed backwards.
Construction of the sprocket on a Chinese chainsaw
Depending on tool design, the dismounting process for the products in question will differ.
This is interesting! To extend the service life of the chainsaw driving sprocket, it is necessary to run in the tool and not to overload it while working, which depends on the purpose (domestic, semi-professional or professional). With a domestic tool it is possible to cut wood, but the saw is not designed for this purpose, and frequent use with overloading will lead to wear of the component parts.
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Chainsaw drive sprocket design
The chainsaw design has not only a drive sprocket, but also a driven sprocket. The chainsaw’s drive sprocket is in the tool’s structure, while the slave sprocket is at the end of the bar. The purpose of the slave unit is to equalize the tension and direction of travel of the chain sprocket.
Drives come in one piece and as a complete unit. Solid pieces consist of a hub with a pressed on ring gear. When replacing the pinion, the complete mechanism is disassembled, because the gear construction is inseparable. 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 simple design of the mechanism. Only one pinion is replaced, which costs half as much as a complete mechanism. The following signs are an indication of proper wear on the gears:
- Existence of large radii at tooth junction points
- Uneven tooth width
- Detection of chips and metal shavings on the top of the gears
- Scoring and risks on the inside surface of the holes in the hub
- Jamming of the chain is detected when the tool is started
If the drive unit is worn, it is imperative that it be replaced. To do this yourself, you must first disassemble the machine and determine the type of chain saw that is fitted. If even the tool has a non-disassembled pinion, you can install a prefabricated mechanism instead of it, which is more rational.
There are two types of installation of drive sprockets on chainsaws. The first way is to put the pinion on the outside. This design is the most common on STIHL chain saws. The construction of such a device is shown in the photo below.
The product of the non-disassembled type on the tool
The second variant is characteristic for the tools of Chinese origin. The gear teeth are on the inside instead of the outside, i.e. the unit is reversed.
Construction of the sprocket 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 extend the service life of the chain saw drive sprocket, it is necessary to pass the running-in of the tool, and at work not to overload it, which depends on the purpose (domestic, semi-professional or professional). You can cut wood with a household tool, but the saw wasn’t designed for that, and frequent use with overloading will wear out the components.
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When and why a worn chainsaw chain sprocket needs to be replaced
The chain sprocket of a chainsaw or electric chainsaw is one of the most important parts of your saw. The chain saw sprocket’s main function: to transmit engine torque to the saw chain. This transfer takes place through a centrifugal clutch. According to the types of sprockets can be divided into professional and household, as well as chains. The sprocket, like the chain, will gradually wear out as you use the chain saw and cut wood.
Let’s learn more about why a worn chainsaw or electric chainsaw sprocket needs to be replaced and when it’s best to do so.
The main signs that the sprocket needs to be replaced:
- your chain saw has been changed twice (one of the rules of chain saw and electric saw operation is that if you use the tool often and actively, you should change the drive sprocket after two chain changes);
- the cutting quality has deteriorated and the chain needs tightening more often;
- you have installed a new chain to which the old sprocket does not fit (this part is not universal and also has its own pitch, in addition, the pitch of the chain sprocket and the chain sprocket must be the same, otherwise the tool will not work);
- you are using a different tire, a shorter or a longer one.
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When and why a worn chainsaw sprocket needs to be replaced
The chain saw or electric chainsaw drive sprocket is one of the most important parts of the saw. Main function of a chainsaw sprocket: to transmit engine torque to the saw chain. This transmission is through a centrifugal clutch. Sprockets can be divided into professional and household sprockets, like chains. As you use your chainsaw and cut wood, the drive sprocket, like the chain, will gradually wear out.
Let’s learn more about why a worn chainsaw or electric chainsaw sprocket needs to be replaced and when it’s best to do it.
The main signs that a sprocket needs to be replaced are:
- your chainsaw has had the chain replaced twice (one of the rules of chainsaw and electric saw operation is that you should replace the drive sprocket after two chain changes if the tool is used frequently and actively);
- the cutting quality has deteriorated and the chain needs tightening more often;
- you have installed a new chain to which the old drive sprocket does not fit (this part is not universal, and also has its own pitch, in addition, the steps of the drive and idler sprockets of the chain must match, otherwise the tool will not work);
- you are using a different bar, a shorter or a longer one.
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How to remove and change the chain sprocket on a chainsaw
Before you remove and replace the sprocket on a chainsaw, you need to make sure that the part is not subject to further use. To do this, you need to inspect the part, and a photo of a new and worn chainsaw sprocket is shown in the photo below.
Shown on the left is a new part, and on the right the device shows clear signs of wear. If you find a chipped gear tooth after removing the tool guard, the part has to be replaced. To do this, you need to buy a sprocket in a tool store or in an online store, where the choice is much greater, which will allow you to choose the best option.
To change the sprocket, you need to decide what type of device is on the tool and what will be installed. For each type of mechanism, the sequence of operations will be different. Replacement of the sprocket on the chainsaw of the first variant of the non-disassembled type is as follows:
How to remove the protective cover on a power tool
Assemble the mechanism in the reverse order. If you need to replace a collapsible-type product, the process is almost the same, only in the end a single ring gear is replaced without the drum.
Constructive differences between solid and collapsible gears
If the replacement process is complete, you need to perform a check. Check the tensioning force of the chain by activating the handbrake and pulling the chain in the direction of movement. Immobility of the product indicates the overtightening of the mount. Release the tensioner to loosen it.
This is interesting! When replacing the mechanism in question, it is recommended to buy a special suitable repair kit for a particular model of tool, depending on the pitch of the chain.
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How the chain saw’s main drive sprocket works
Almost all modern chainsaw models have a centrifugal clutch system. The specificity of this mechanism is that when the petrol engine reaches the maximum number of revolutions, the clutch drum starts automatically, transferring the rotation exactly to the drive sprocket. This reduces stress on the tool’s base parts, extending service life and maximizing productivity.
Figure 1. Schematic diagram of the drive sprocket
The clutch drum, where the sprocket is located, can be on the inside or outside of the chainsaw body. There is always a cover on top to protect the moving parts from dirt, sawdust, and dust. The clutch itself is a metal disk located in the clutch drum. The whole mechanism is attached to the engine crankshaft by bolts with springs, on the edges of which there are friction pads. When the engine speed exceeds a certain value, there is a centrifugal force that exerts a strong pressure on the inner part of the drum. After that the sprocket starts. the chain saw starts to rotate.
Important! The sprocket is what drives the chain saw chain. All parts of this mechanism are closely linked and if the headset fails, the tool will not work properly.
What tools do you need to change the sprocket?
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 do not come with such a wrench);
- An aluminum or copper hammer (soft metals only and only if you don’t have a wrench);
- A hammer (for hammering the hammer while unscrewing the sprocket);
- a flat-blade screwdriver for tightening the nut
- Sprocket bearing grease.
How to remove the sprocket from a chainsaw: several options for different clutch drum designs
Method for sprocket with fixed sprocket
- dismantle the protective cover and the bar and cutter bar;
- locking the piston part of the motor;
- disconnect the clutch from the motor system;
- Remove the clutch clutch and centrifugal sprocket from the saw housing;
- visual inspection of the sprocket and its toothed part;
- replacement of the sprocket with a new clutch drum if defects are found;
- Diagnosis of chainsaw clutch elements for defects. worn centrifugal springs and cams can adversely affect the operation of the sprocket;
- if there are no faults, you can proceed to the assembly stage. To do this: remove the stopper;
- pull back the ignition cable;
- screw a stopper to fix it on the motor shaft of the centrifugal mechanism;
- using a universal wrench in the opposite direction to the chain travel, clamp the clutch;
- return the remaining removed parts to their original positions.
Method for a sprocket with a collapsible clutch drum
The second method on how to unscrew the sprocket on a chainsaw with a collapsible clutch drum looks more simplified compared to the previous one. The sequence of operations will be similar, but it will be disassembled and reinstalled not the whole sprocket, but only its separate part. the ring gear. Don’t forget that installing a new chain on your chainsaw bar is one reason to retrofit your saw with a new sprocket. Otherwise, the chain will stretch prematurely or break while you’re working. Less wear on the clutch drum is obtained by alternating the use of several chains and periodic maintenance of the clutch bearing. This mechanism is only engaged when idling: it is not engaged at higher rpm. Experts recommend changing it simultaneously with the chain and sprocket, and systematically lubricating it with chain oil.
The main reasons for replacing the drive sprocket
A universal spanner is the main tool when replacing a sprocket.
The most common reasons that cause the tool to be repaired to replace the drive sprocket are:
- jamming of the chain due to faults in the chain while the machine is running;
- high sprocket wear caused by prolonged use of the machine.
If the chain sprocket is used regularly, it will become worn out because of the increased stress placed on it when sawing wood. There are two ways to operate the unit:
In the first method of operation, the chain is operated until it is completely worn out. This method has a few disadvantages. The main disadvantage is that it is difficult to check the wear during intensive machine operation.
If two or more chains are used in the process, it is possible to achieve even wear of the chain and sprocket, which allows to prolong the period of operation of the device before the repair consisting in replacement of the sprocket. In addition to sprocket wear, remember the bearing that is mounted in the sprocket. This component is designed to operate at all engine speeds. If you change the sprocket, you should also change the bearing at the same time.
The clutch and sprocket must be replaced on time. If repair work is not performed on time, the tool will vibrate and wear out the bearings in the internal combustion engine on the crankshaft halves. The sprocket teeth should not have a maximum wear limit of 0.5 mm. Sprocket life is twice as long as a single chain, so two chains should be used when working. After the chain has used up its service life, it is necessary to replace the chain and sprocket at the same time.
chainring replacement for chainsaws of different brands
When replacing or repairing the chain saw it is necessary to take into account the constructional features of the model. Specifics of the service of the coupling drum of the popular manufacturers:
- STIHL. Husqvarna brand name has both solid and collapsible sprockets. A 19 mm head and a screwdriver are needed to unscrew the clutch. Note that the threads are left-handed and there is a deflector plate behind the clutch (consumable, often breaks when diagnosing the drum).
- Partner. The particularity of this brand is that it is recommended to change sprocket and bearing as well. If this step is ignored, there is a risk of chain malfunction, pitch change during active sawing after a scheduled repair.
- Husqvarna (Husqvarna). Many Husqvarna models use a sprocket with a replacement crown. This makes routine replacement and repair that much easier. A 13 mm open-end wrench is needed to hold the shaft at the impeller side when disassembling the tool.
- Carver. Unlike other manufacturers, there are no specific features of the clutch design. Depending on brand, the sprocket is either solid or collapsible.
Even before beginning a routine repair, it is advisable to read the manual carefully. It indicates important features of the saw’s design, frequency of replacement of consumable parts.
How to reduce wear on the drive sprocket?
The service life of the chainsaw clutch can be extended with routine preventive maintenance and quality service of the tool. Helpful hints:
- Apply grease to the needle bearing after each sprocket change;
- Choose all the parts of the saw set correctly according to the chain pitch and use reliable consumable parts;
- Do not replace parts of the clutch and saw at the same time. this leads to a change in pitch, wear of the headset;
- Clean saw regularly by removing the side cover.
Monitor carefully the sound and behavior of the chain during operation. If it starts to jam, there is vibration and rattling. diagnosis is needed.
Replacing the sprocket in a chainsaw is a planned procedure that ensures the reliable and stable operation of the tool. When diagnosing or repairing the coupling mechanism, you should consider the design features of the model, the requirements of the manufacturer. To avoid frequent breakdowns, it is recommended to use only original parts or quality analogues, systematically clean the chainsaw.