How to Change a Drive Sprocket on a Chainsaw

a little about how to use it

Regardless of the brand of the manufacturer (STIHL, Husqvarna, Partner, Patriot, Makita ) chain saws are divided into domestic, semi-professional and professional. The difference, however, does not lie in the quality of assembly or the manufacture of the components, but rather in the class of the tasks to be performed, the performance and the long service life of the drive. This predetermines the choice of material for the chainsaw drive sprocket, its design and the design of the saw chain.

The performance of the tool will be determined by the way the chain-and-sprocket pair is used. In most cases, users use one of two options:

  • The chain is used until the teeth are completely worn out, at which point both the saw blade and the sprocket are replaced at the same time;
  • Changing chains with different pitch and each chain requires a different sprocket drive sprocket.

The choice of variant is often determined by the owner’s attitude toward his tool. If you don’t care what you are sawing (wood or steel clips, screws, etc.), you can choose the first option.), so it is possible to choose the first variant. The chain, however, will have to be dressed periodically, thereby reducing the performance of the chainsaw.

It is categorically not recommended to leave the old chain with a new sprocket and vice versa. If the saw blade is worn, it’s almost 100 percent likely that the pitch will be out of sync. That’s why both chain drive components will be exposed to high dynamic stress at the initial startup. This will either cause the chain to stretch prematurely “adjusting” to the sprocket or one of the teeth on the drive sprocket will break on impact.

In addition, the function of the sprocket shaft bearings is also worth considering. Only the crankshaft rotates when the saw is in working mode. But all chain saws also occasionally run dry when the bearing is rotating. Lack of lubrication leads to wear of the seating surfaces and. as a consequence. to additional run-out of teeth of still quite serviceable chain transmission.

So when replacing the chain and drive sprocket on a chainsaw, it’s a good idea to replace the bearing and the chain sprocket at the same time.

Changing the Drive Sprocket on a Husqvarna Chainsaw

There are dozens of chainsaws by different manufacturers, capacities and, most importantly, for special applications. Divide saws into:

Accordingly, their drive pinion will be different, as well as the sequence of actions. This is a peculiarity of saw gearboxes. Most professional tools can change its location on the saw in two planes.

The main chain saw malfunctions and actions to fix them are described here.

Changing the chain sprocket on a chainsaw. how to remove and change it with your own hands

Gasoline chain saws, like most other tools, require periodic diagnosis of failures and replacement of worn parts. A large part of them are related to the chainsaw drive sprocket or clutch disc. one of the important elements of all chainsaws without exception. Despite the relative simplicity of its construction and the hints of the instruction manual, every year thousands of inexperienced craftsmen get stumped on this issue and spend money on service centers or produce it incorrectly, thus further exacerbating the problem.

That’s why we will focus on this topic and understand the structure, functional features and repair of this working unit of chainsaws.

Design of chainsaw clutch system

Husqvarna, STIHL, Partner and most other brand name chainsaws have a centrifugal clutch. It is engaged automatically when the engine reaches a certain speed.

The clutch basket is shaped like a disc. It has movable friction pads that can move radially. In the normal state, they are pressed against the center by the built-in springs without touching the drum of the chain drive sprocket.

When the engine is running at a preset RPM, centrifugal forces act on the shaft to which the clutch basket is attached, exceeding the force of the springs. The friction lining elements move to the sides, pressing against the inner surfaces of the sprocket drum, which begins to rotate at the desired frequency. Such a system can protect the engine from serious damage if the chain jams.

How to change the gas chainsaw clutch and drive sprocket

Depending on the model, the sprocket is located on the outside or inside of the clutch assembly. For safety purposes, this whole assembly with part of the guide bar is covered with a protective cover.

How to remove the drive sprocket from a chainsaw yourself and replace it with a new one

No matter what manufacturer makes a chainsaw and no matter how reliable it is, wear and tear occurs over time on the rubbing parts. These include the chain, bar, and sprocket of the chain drive. Even if the wear is only a fraction of a millimeter, it affects the entire tool and its performance.

The sprocket is the driving element that makes the chainsaw run.

Causes of failure and how to determine if it needs to be replaced

Wear on the drive sprocket teeth can occur for a number of reasons:

  • natural wear along with the chain teeth
  • accelerated wear as a result of excessive tension or lack of chain lubrication;
  • improperly selected chain;
  • manufacturing defect.

Metal wear can be determined visually by examining the sprocket without removing it from the saw. Dents and chips on the surface must not exceed 0.5 mm.

The need for replacement is determined by an increased noise in the movement of the chain, but this is characteristic only in the presence of deep potholes. Shallow running is difficult to see, but it will cause heavy wear on the chain. If the teeth are broken, the chain can move jerkily, which is particularly felt during operation.

What tools do you need for changing a sprocket?

To replace a 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 have such a wrench);
  • an aluminum or copper pry bar (soft metals only and only if a wrench is not available);
  • a hammer (to tap the tapper while unscrewing the sprocket);
  • a flathead screwdriver to tighten the nut;
  • grease for the sprocket bearing.

The following are some basic reasons for changing a chain sprocket

A universal wrench is the main tool you will need when replacing a sprocket.

The most common reasons for tool repairs involving the replacement of the drive sprocket are:

  • jamming of the chain due to faults in the chain while the machine is operating;
  • high wear on the sprocket as a result of prolonged use of the machine.

High wear on the drive sprocket due to excessive loads during woodcutting operations if the attachment is used regularly. There are two ways of operating the unit:

In the first type of operation, the chain is operated until it is completely worn out. This method has several disadvantages. The main reason for this is the problem with monitoring wear during heavy use of the machine.

If two or more chains are used in the process, the wear on the chains and sprocket can be evenly distributed, helping to extend the life of the machine before a repair consisting of replacing the sprocket. In addition to wear of the sprocket, do not forget about the bearing, which is installed in the sprocket. This component works at all engine speeds. If the sprocket is replaced, the bearing must be replaced at the same time.

The clutch and sprocket assembly should be replaced in good time. In case of untimely repair work during operation the tool has increased vibration, which leads to increased wear of the bearings installed in the internal combustion engine on the crankshaft halves. Maximum depth of sprocket teeth wear should not exceed 0.5 mm. Sprocket life is twice as long as a single chain; therefore, two chains should be used when working. After the chains have reached the end of their service life, the chains and the chain sprocket should be replaced at the same time.

How to remove and change a chain sprocket on a chainsaw

Before you remove and replace the chain sprocket on your chainsaw, make sure it is no longer serviceable. 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.

On the left you can see the new part, and on the right the device has obvious signs of wear. If after removing the tool guard a chipped gear tooth is found, the part must 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 pinion, you need to decide what kind of device is on the tool and what will be installed. The sequence of operations will be different for each type of mechanism. Replacing the sprocket on a chainsaw of the first variant of the non-disassembled type looks as follows:

In reverse order the process of assembling the mechanism is carried out. If you need to replace a collapsible sprocket, the process is almost the same, but you end up replacing one sprocket without the drum.

If the replacement process is completed, you need to check. Check the strength of the tension of the chain, for which the handbrake is activated, and the chain is pulled in the direction of its movement. If the product does not move, it indicates that the fastener is tightened too much. To loosen it, you need to release the tensioner.