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Chainsaw Seized Up. Tips from a Professional

A chainsaw is seized when it fails to crank up after repeated pulls of its starter chord. Professionals and homesteaders who frequently work with a saw might have gone through this experience. It is quite typical in chainsaws that are subjected to recurrent use and have undergone considerable wear. In this blog post, I shall discuss everything you need to know if your chainsaw gets seized up.

Chainsaw seized up. Tips from a professional.

When a chainsaw gets seized, it can be due to a fault in the pull-chord assembly or a failure in the piston-cylinder mechanism. Generally, most cases of engine seizures can be repaired if the damage hasn’t been done to the engine components, in which the saw may not be operable again. Factors such as overheating, revving up at WOT, improper fuel mix, and dust exposure elevate the risk leading up to engine seizures.

To gain a deeper insight into the problem and the possible solution strategies, I will explain the issue and how to unlock a chainsaw.

What Causes a Chainsaw to Seize?

A chainsaw is said to be seized when the piston head, due to thermal expansion, gets jammed in the cylinder making the crankshaft unable to rotate. Factors such as incorrect fuel mix, overheating, and overrevving raise the risk of a seizure.

These risk factors are described in detail as follows:

1. Incorrect Fuel Mix:

Always ensure that the fuel-to-oil ratio is set to 50:1. Keep in mind that chainsaw pistons slide from top to bottom nearly 6000-12,000 times per minute when in action. You can realize how much wear the components must endure at such high speeds and temperatures.

Thus, we add a lubricant mixed with the fuel to prevent piston and ring failure by reducing friction and preventing overheating. If this ratio is disrupted, the rings and piston may overheat, causing the engine to seize.

2. Revving when cold:

When your saw is cold started, avoid running it at WOT (wide open throttle). The sudden cranking up of your engine RPMs can elevate temperatures quickly, causing damage to your engine’s gaskets and rings. During the winter, start your saw at a slower RPM and gradually increase the speed.

3. Running Lean: 

A lean run is one in which the air-fuel mixture contains a higher amount of air. Running your engine lean raises the maximum temperature of the components, causing them to overheat. A lean run is most commonly caused by ethanol-blend fuel, which creates oxygen and causes the mixture to be lean. Always use ethanol-free fuel and make sure your carburetor is set to run rich to keep the engine cool.

4. Overheating:

It is worth noting that overheating your chainsaw is the quickest way to wreck it. It could harm the chain, clutch, and guide bar, and even melt the plastic case and affect the engine components. It may also cause the bar oil to evaporate, causing overheating and chain damage. I’ve seen a lot of cases with brand-new saws producing smoke when they’re running at full power.

You must ensure that the cooling system is not clogged with debris and that air flows through the cylinder unrestricted. Secondly, never operate your saw at full throttle when it’s stuck, as this might lead to overheating. The increased load raises the likelihood of piston failure in your engine considerably.

How do you know if your Chainsaw is Seized?

If your chainsaw fails to start after multiple pulls on the cord, it is considered to be seized. A seizure is usually caused by a problem with the engine or the flywheel-pull cord mechanism.

Starting an engine demands the presence of three major agents: suitable compression, spark, and an adequate fuel supply. The unavailability of any single factor stops it from commencing. The arrangement when the piston reaches the top dead center of the cylinder is referred to as compression.

As a result, the air-fuel mixture is squeezed, raising the temperature and pressure. The spark plug ignites the already volatile fuel mixture as soon as compression occurs. This starts the combustion process, which forces the piston downwards and supplies power to the crankshaft.

In the event of a seizure, a breakdown in key components inhibits the engine compression. It could be a faulty pull cord or a faulty flywheel. In the worst-case scenario, it might be a jammed cylinder or a damaged crankshaft. This is referred to as an engine seizure.

Can you Fix a Seized Chainsaw?

In most instances, a seized chainsaw can be repaired if the engine’s components are not damaged. Generally, the problem lies with the pull cord mechanism or the flywheel.

A chainsaw that doesn’t start might work as such due to a variety of factors. The fuel tank could be empty, or the filters could be clogged. A chainsaw that has been locked up is the one in which the pull cord does not engage the flywheel.

The issue is either with the pull cord-flywheel system or with the engine’s piston cylinders. The former is simpler to troubleshoot and repair, whilst the latter may require the services of a professional or, in some cases, may render the chainsaw inoperable.

To answer the question, a seized chainsaw can be restored in most cases. In the following section, we’ll look at how this can be accomplished.

How do you Unlock a Chainsaw?

Let’s start with a troubleshooting strategy to find a solution to our problem. We’ll begin with the simplest measures and work our way up to somewhat more difficult ones if the problem persists.

Before removing any of the components, make sure there isn’t any debris or wood scrap lodged between the chain and bar, preventing it from freely rotating. Clean the blade with a rag and use a screwdriver to pull out the stuck wooden fragments between the chain and bar.

1. Chain Brake:

In most cases, the issue is with the chain brake, as most users lock their chain while storing it and forget to unlock it before sawing again.

Chain brakes are built-in safety features in chainsaws that are intended to protect against kickbacks. When the brakes are applied, the chain becomes stuck and does not move. The chain brake is located next to the handle. If your chainsaw gets stuck, try pulling the chain brake until you hear a click. This step releases the brakes, allowing you to move the chain. If the chainsaw is still stuck, move on to step 2.

2. Access the Engine:

With the brake released, let’s look at the engine’s compression. If the engine pistons are stuck in their cylinders or if the crankshaft seems bent, this is an indication of an engine seizure, and, as a result, your chainsaw will be locked up. The following method will determine whether the problem is with your engine or elsewhere, as engine seizures will likely leave your chainsaw unusable.

– Compression test: 

 By running a compression test on your engine, we can assess whether or not enough compression is produced. You can find a compression testing gauge at your local dealer or various online stores.

Remove the spark plug from its socket with a wrench. Connect the compression tester’s hose to the hole in the spark plug. Pull the chainsaw cord at least five times and take note of the reading on the tester’s gauge.

  • Case 1: Cylinder wall scoring: As a rule of thumb, this value must be more than 100 psi for combustion to begin. Your piston and cylinder may have been scored if this is not the case. In that situation, you should take your equipment to a professional for repair.
  • Case 2: Engine seizure: If no compression is recorded on the gauge, your engine is most likely seized, and you should consider purchasing a new chainsaw.
  • Case 3: Normal compression: If the compression exceeds 100 psi and the problem persists, you should continue to the next step.

3. Disassembly:

In this stage, we’ll look at the pull cord as well as the flywheel. However, certain parts must be disassembled to gain accessibility to the pull cord mechanism.

– Clutch covering:

Before disassembling the chainsaw, ensure the engine is off and activate the engine stop switch. To remove the clutch cover from the saw, unscrew the nuts on the clutch cover. To remove the nuts, turn them counterclockwise with a socket wrench of the appropriate size until they are loose. The pull cord mechanism will be entirely visible with the clutch cover off.

– Bar and chain:

Next, pull the guide bar forward and away from the chain saw’s body to remove both the guide bar and the chain. The strain in the chain will release, allowing you to detach the chain from the guide bar and draw it out.

– Spark plug cover:

Remove the spark plug cover, which is the chainsaw’s top cover, by unscrewing the screws that hold it in place. To remove the spark plug, use a socket wrench to unscrew it after removing the spark plug boot that covers it. The flywheel of your chainsaw is now completely exposed.

4. Examine the Flywheel:

Now you must examine the flywheel to see if there are any signs of wear or damage. Check to see if any of its vanes are damaged. If the flywheel appears to be damaged, you should consider replacing it. But first, rotate it to see if it makes contact with the cover’s side bolts. If the flywheel rotates smoothly on the shaft while you can detect the compression of the pistons, your engine is in good working order, and no signs of engine seizure exist.

Nonetheless, examining the flywheel will indicate whether the problem is with the engine or with the flywheel itself. If both are satisfactory, move on to the following step, which is to inspect the pull cord.

5. Check the Pull cord:

A spring-loaded device allows the pull cord to roll onto a disc. Check to ensure that the spring is not dislocated or broken and that the pull cord is not tangled. If the pull cord appears to be broken, you should replace it. The spring mechanism and the pull cord are low-cost items that may be purchased at a hardware shop or ordered online.

6. Inspect the Spark Plug:

A faulty spark plug could be another cause of a chainsaw seizing up. The spark plug initiates spark during the engine’s compression stroke resulting in combustion. The engine will not start if there is no firing in it.

As mentioned in step 2, the spark plug is located beneath the cover at the top of the chainsaw. Remove the cover to reveal the plug. After the boot has been removed, remove the spark plug with a wrench.

Examine the spark plug electrodes carefully to see if there is any buildup of carbon deposits. Dislodge any existing debris with a brush. If available, a feeler gauge can be used to measure the spacing between the electrodes and see if it exceeds the tolerance value for that specific plug. If the spacing exceeds, it is time to upgrade your spark plug.

Can a Chainsaw Get too Hot?

Chainsaw indeed can become considerably hot if run at full throttle and not lubricated adequately. Overrevving the chainsaw engine can quickly overheat your device, even if the engine is new.

Most two-stroke chainsaw engines operate between 6000-14000 RPMs. At such high rotational speeds, heat generated due to friction plays a major role that cannot be ruled out. An increase in RPMs raises the device temperature exponentially. In summers, this condition can become increasingly severe.

To prevent your chainsaw from getting too hot, always make sure that the bar and chain are being oiled properly. The oiler tank must be filled, and the oil pump should be in working order so that the heat generated due to friction can be dissipated properly.

What Happens when a Chainsaw Overheats?

When a chainsaw overheats, thermal expansion results in wear and tear of the engine components such as seals and piston rings. It can also wear away the chain and cutting blades. In extreme cases, the plastic casing can melt away due to the extreme heat.

When chainsaws are exposed to elevated temperatures for an extended period, it produces fatigue in the engine’s mechanical components. The piston can expand thermally and score up the cylinder walls. This produces extra stress on the crankshaft and impedes the engine performance. When not resolved, it can also lead to your crankshaft getting fatigued and eventually failing. These failures cannot be fixed, and hence you may need to get yourself a new chainsaw altogether.