How To Remove An Asterisk From A Chainsaw Partner
A chainsaw requires regular diagnosis and periodic replacement of worn parts. With regular use, not only the saw headset, but also the drive sprocket becomes unusable. In this tool, it acts as a clutch disc, due to which it has a significant load both at startup and during operation. The chain saw sprocket has a simple design, so repair and maintenance are easy to do with your own hands. In the article we will consider how to determine the degree of wear of this part and carry out a planned replacement.
Almost all models of modern chainsaws use a centrifugal clutch system. The specificity of this mechanism is that when the maximum number of revolutions of the gasoline engine is reached, the clutch drum starts automatically, transmitting rotation to the drive sprocket. This reduces the load on the basic parts of the tool, prolonging the life and maximum productivity.
Figure 1. Scheme of the device of the leading star
The clutch drum where the sprocket is located may be located on the inside or outside of the chainsaw body. There is always a lid on top to protect moving machinery from dirt, sawdust and dust. The coupling itself is a metal disc located in the coupling drum. The whole mechanism is mounted on the crankshaft of the engine with bolts with springs, on the edges of which friction pads are located. When the engine speed exceeds a certain value, a centrifugal force occurs, exerting strong pressure on the inside of the drum. After that, an asterisk starts. The rotation of the chain saw begins.
Important! It is the sprocket that drives the chain of the chainsaw. All parts of this mechanism are closely interconnected, damage to the headset leads to disruption of the instrument.
Kinds of stars
Depending on the class of the chainsaw, all the stars are divided into two groups. Professional and household. The first type of parts have increased wear resistance, made of durable metal alloys, not subject to corrosion and mechanical damage. Households often require replacement and scheduled repairs, with the active use of the tool, diagnostics are recommended every six months. By design features, the following types of stars can be distinguished:
- National teams. The removable crown easily unscrews from the axis of the drum, which simplifies the inspection and replacement of this part. Almost all European chainsaw models are equipped with such stars.
- Whole. They consist of a hub and a stationary crown (the number of teeth may be different, you must carefully read the instructions for the chainsaw). Due to the factory press fitting, the crown cannot be removed separately from the hub, therefore, if the breakage occurs, it is necessary to disassemble the entire clutch drum. Such a mechanism is usually found on Chinese models.
If you plan on your own to service a chainsaw, it is recommended to purchase a tool with a professional type of drive sprocket. It should be collapsible, which reduces the cost of repair and maintenance of the tool.
When is a replacement needed?
The saw headset and drive sprocket are subject to natural wear during operation. This is not a breakdown, but a routine tool maintenance procedure. Reasons to replace sprockets:
- Intensive and continuous operation of the saw;
- Mechanical shock to the headset;
- Use of the wrong chain. Figure 2. Leading star on a chainsaw
Normal wear of the teeth of the drive sprocket is up to 0.5 mm. With regular operation, this indicator can reach up to 1 mm, but over time it will lead to a load on the engine, damage to other parts of the saw. The following signs can determine the need for replacement or repair:
- There is mechanical damage on the guide sprocket;
- The width of the teeth is disproportionate to their height;
- There are asymmetric angles;
- On a nave there are chips, furrows or large barbs.
If you do not timely diagnose and prevent the moving parts of the chainsaw, the vibration increases and the effect on the bearings of the crankshaft increases. As a result, this leads to costly repairs, serious damage to the tool.
Important! Manufacturers recommend inspecting the coupling drum when the chain comes in contact with a metal object during sawing.
How to change a star on a chainsaw?
If the chain begins to vibrate even at low speeds, the chainsaw is operated for a long time without replacing parts. It is required
Carry out diagnostics and, if necessary, change the components of the saw headset. For a planned replacement, you will need a new clutch drum or whisk, depending on the specific model, a basic set of tools:
- Candle key;
- Cable up to 15 cm long or piston stopper;
- Factory wrench for coupling removal;
- Adjustable spanner or wrench. Figure 3. Necessary tools for replacing a star
It is recommended to have a round file, pliers, a vice and a knife to eliminate defects in the design from the chain headset (if only tooth correction is required).
How to unscrew?
It is easy to remove and replace this part yourself. Work technology:
- Fasten the piston to the saw cylinder. First, remove the protective cover on the housing, the air filter and unscrew the spark plug. Install a special piston stopper in the formed hole. You can use a tight nylon cord or wire up to 15 cm long instead. If the piston interferes, you can slightly twist the sprocket or move the chain clockwise.
- Remove the bolts on the cover that secures the tire, remove the protective cover. Release chain tension or remove saw headset. At the same time, dust, dirt and sawdust can be cleaned.
- Depending on the model, the sprocket acts as an element of the clutch drum or to be built in separately. In the second option, remove this part, replace with a new one. The one-piece design is difficult to repair. You need to disassemble the unit. To do this, unscrew the coupling clockwise, remove the drum. Check structural parts for wear and deformation. Figure 4. Replacing a star with a new one
If the sprocket is an element of the clutch drum, then the entire part will have to be changed. When replacing, you should pay attention to the conformity of the model. It should be similar to the factory one.
How to assemble?
Hitch assembly should be done in reverse order. First install the sprocket on the needle bearing, then put on the drum, washer, gasket and the coupling itself. Tighten counterclockwise, gently lock the piston.
If the chainsaw has an oil drive spring, it can be integrated into the drive sprocket. In most models, the correct location of this element is marked with a special color or notch. To get to the desired position, turn the sprocket until it clicks.
The final stage of assembly is the installation of the saw bar. During this process, it is required to release the hand brake and then check that the teeth of the chain are in the corresponding grooves. After installation, mount the chainsaw chain to working condition. At the end, remove the stopper, screw in the spark plug and replace the filter. The final step of the repair is fixing the protective cover of the case.
Features of replacing the star for chainsaws of different brands
When replacing or repairing a chainsaw, the design features of the model should be considered. Specificity of service of a coupling drum of popular manufacturers:
- Stihl (stihl). Models of this brand have integral and collapsible types of stars. To unwind the clutch, you need a 19 head and a knob. It should be noted that the thread is left, and a reflective plate is installed behind the clutch (consumable material, it often breaks when diagnosing a drum).
- Partner (Partner). The peculiarity of this brand is that when replacing the sprocket, it is recommended to change the bearing. If you ignore this step, after a scheduled repair, there is a risk of chain disruption, change in pitch with active sawing.
- Husqvarna (Husqvarna). Many Husqvarna models use an interchangeable crown sprocket. This simplifies scheduled replacement and repair. When parsing the tool, a 13 key is required to fix the shaft on the impeller side.
- Carver (Carver) Unlike other manufacturers, there are no specific features of the clutch design. Depending on the brand, the star can be solid or collapsible.
Before starting a scheduled repair, it is recommended that you carefully read the instructions. It indicates important design features of the saw, the frequency of replacement of consumables.
How to reduce lead star wear?
The life of the clutch of a chainsaw can be increased by scheduled maintenance and quality service of the tool. Helpful hints:
- Apply grease to the needle bearing after each sprocket change;
- Correctly select all parts of the saw set depending on the chain pitch, use reliable consumables;
- Do not replace the clutch and saw parts at the same time. This leads to a change in pitch, wear of the headset;
- Regularly clean the saw by removing the side cover.
During operation, you should carefully monitor the sound and behavior of the circuit. If it starts to jam, vibration and rattling appear. Diagnostics are required.
Replacing the sprocket in a chainsaw is a planned procedure that ensures reliable and stable operation of the tool. When diagnosing or repairing the coupling mechanism, the design features of the model and the manufacturer’s requirements should be taken into account. To avoid frequent breakdowns, it is recommended to use only original parts or high-quality analogs, systematically clean the chainsaw.