Chainsaw Locked Up: Tips from a Professional


One of the most common problems most homesteaders encounter is their chainsaws getting locked up. This condition usually occurs in gasoline-powered chainsaws where the engine just doesn’t start as the cord is pulled continuously. There can be various reasons that can cause this problem. Being a professional in this field, I shall discuss the factors that may lead to your saw getting locked up in this blog post.

Chainsaw locked up, how to fix? Consider following these steps:

  • First, make sure the chain brake is disengaged and the chain runs freely.
  • Using a compression tester, check if the engine produces any compression.
  • Examine the flywheel to see if it runs freely. Replace it if damaged.
  • Inspect the pull cord mechanism and replace it with a new one if it’s broken.
  • Check the spark plug’s electrodes for any signs of wear.

If you’re witnessing this problem for the first time or are interested in fixing it on your own, try giving this article a read as we’ve discussed everything related to seizures and locks-ups comprehensively.

How do you know if your Chainsaw is Seized?

If your chainsaw doesn’t start at all after pulling the cord multiple times, it is said to be seized. A seizure usually refers to a fault within the engine components or the flywheel-pull cord mechanism.

Starting an engine requires three main agents to play their role i.e., adequate compression, spark initiation, and adequate fuel supply. The absence of any single factor prevents it from starting. Compression refers to the setting when the piston reaches the cylinder’s top dead center. As a result, it squeezes the air-fuel mixture, thus raising its temperature and pressure. As soon as the compression occurs, the spark plug ignites the already volatile fuel mixture. This initiates combustion which drives the piston downwards and thus delivers power to the crankshaft.

In case of seizure, a failure in certain components prevents the engine from undergoing compression. It could be a broken pull cord or a damaged flywheel. Or in worst cases, it can be a jammed cylinder or a bent crankshaft. This condition is known as engine seizure.

Can a Seized Chainsaw be Fixed?

A seized chainsaw can be fixed in most cases provided the engine’s components aren’t damaged. Typically, the fault lies either in the pull cord mechanism or the flywheel.

A chainsaw that doesn’t start has numerous causes behind it. The fuel tank may be empty or the filter might be clogged etc. A locked-up chainsaw is a special case in which the pull cord doesn’t engage the flywheel. The problem lies either in the pull cord-flywheel assembly or in the piston cylinders of the engine. The former is easier to troubleshoot and fix while the latter may require the aid of a professional or in some cases, may render the device inoperable.

Hence, to answer the question, a seized chainsaw can be fixed in most cases. Let’s see how we can do that in the next section.

How do I Fix my Locked Chainsaw?

Let’s take a troubleshooting approach to land into the solution of our problem. We shall begin with the easiest steps and if the problem persists, we’ll proceed to slightly advanced steps.

Before we remove any of the components, you should ensure that there isn’t any debris or wooden scrap stuck between the chain and bar which prevents it from rotating freely. Use a rag to clean the blade and pluck out the stuck wooden scraps between chains using a screwdriver.

1.  Chain Brake:

In the majority of the cases, the problem lies in the chain brake as most users keep their chain locked while storing and forget to unlock it while sawing again.

The chain brake is an in-built safety feature in chainsaws that are designed for protection against kickbacks. By engaging the brakes, the chain gets locked up and doesn’t move. The chain brake is present adjacent to the handle. If your chainsaw appears locked up, try pulling the chain brake back until it gives a click. This step disengages the brakes and you can move your chain now. If the chainsaw is still jammed, let’s proceed to step 2.

2. Access the Engine:

With the brake disengaged, let’s dissect further by examining the engine’s compression. If the pistons of your engine are jammed in their cylinders or the crankshaft is bent, it’s a sign of engine seizure and as a result, your chainsaw would be locked up. This step will determine whether the fault lies within your engine or elsewhere as engine seizures are most likely to render your chainsaw unusable.

– Compression test:

By performing a compression test on your engine, we can determine whether enough compression is produced or not. You can buy a compression testing gauge from the link given below. http://amzn.to/2jGmoOC

Using a wrench, remove the spark plug from its socket. Connect the compression tester’s hose to the spark plug’s hole. Now, pull your chainsaw’s cord at least five times and notice the reading on the tester’s gauge.

As a rule of thumb, this value has to be above 100 psi for combustion to initiate. If that’s not the case, then your piston and cylinder might be scored. In that case, you need to take your device to a professional. If no compression is recorded at the gauge, then most probably your engine is seized and you should consider investing in a new chainsaw.

If the compression comes to be greater than 100 psi and the problem persists, you should proceed to the next step.

3. Disassembly:

In this step, we shall examine both the pull cord and the flywheel. However, we need to disassemble certain parts before they can be accessed.

– Clutch cover:

Make sure the engine is turned off and the engine stop switch is activated before dismantling the chain saw. Unscrew the nuts on the clutch cover to remove it from the saw. To remove the nuts, use a socket wrench of the right size to turn them counterclockwise until they are loose. With the clutch cover removed, the pull cord mechanism will be completely visible.

– Bar and chain:

After that, pull the guide bar forward, away from the chain saw’s body, to remove both the guide bar and chain. The tension in the chain will ease, enabling you to remove the chain from the guide bar and pull the guide bar out.

– Spark plug cover:

The spark plug cover, which is the chain saw’s top cover, must then be removed by unscrewing the screws that keep it in place. To remove the spark plug, unscrew it with a socket wrench after removing the spark plug boot that covers it. The saw’s flywheel is now totally exposed.

4. Examine the Flywheel:

Now you need to inspect the flywheel and see if any signs of wear or damage are visible. Check if any of its vanes are broken. If it appears damaged, you should consider replacing the flywheel. But before that, try rotating it to see if it makes contact with the side bolts of the cover. If the flywheel rotates freely on the shaft while you can feel the compression of the pistons, then your engine is in good condition and no signs of engine seizure exist.

Nevertheless, examination of the flywheel tells you whether the fault is with the engine or with the flywheel itself. If both are okay, then you should proceed to the next step, i.e., inspect the pull cord.

5. Check the Pull cord:

The pull cord rolls onto a disc through a spring-loaded mechanism. Check to see if the spring isn’t dislodged or broken or if the pull cord isn’t tangled. Replace the pull cord if it seems broken. The spring mechanism and the pull cord are rather inexpensive items that are easily available from a hardware store or you can order them online.

6. Inspect the Spark plug:

Another reason behind a chainsaw getting locked up could be a bad spark plug. As evident from the name, the spark plug provides spark during the combustion stroke of the engine. If no firing occurs in the engine, it wouldn’t start.

As explained in step 2, the spark plug lies underneath the cover which is present at the top of the chainsaw. Remove that cover to expose the plug. Using a wrench, bring the spark plug out after its boot has been removed.

Carefully examine the spark plug electrodes and notice any build-up of carbon deposits is noticeable. Use a brush to dislodge the debris. If available, you can also use a feeler gauge to check the gap between the electrodes and see if it’s beyond the tolerance value for that particular plug. If yes, then it’s time to replace your spark plug.

How to Prevent Engine Seizures in the Future?

Engine seizures dictate the end of an engine’s life. It also means that your chainsaw would no longer be operable as a new engine would cost almost as much as a new device. Among all small engine devices, chainsaws are most vulnerable to seizures due to their operation under large loads and higher RPMs. Being an experienced researcher in this domain, I’ve come across multiple cases of engine failure, and in this section, I’ll discuss the ways by which you can minimize, if not eliminate the chances of engine seizure.

1. Use correct fuel mix:

Make sure the fuel to oil mix is set at 50:1. Keep in mind that during operation, chainsaw pistons move from top and bottom almost 6000-12,000 times a minute. You can realize the amount of wear the components have to undergo at such high speeds and temperatures. To prevent the failure of pistons and rings, we add a lubricant mixed with the fuel which reduces friction and prevents overheating. If this ratio is disturbed, the rings and piston may expand due to overheating, thus seizing the engine.

2. Avoid revving when cold:

Avoid running your saw at WOT (wide open throttle) when it’s cold started. The sudden throttling up of your engine can raise the temperatures abruptly which can damage the gaskets and rings of your engine. In winters, run your saw at slower RPMs for some time and gradually increase the speed.

3. Never run lean:

Lean run means a higher proportion of air in the air-fuel mixture. Running the engine lean raises the maximum temperature within your engine and result in overheating. The most common cause of lean run is ethanol-blended fuel, which produces oxygen and makes the mixture lean. Always use fuel that is free from ethanol and make sure the carburetor is tuned to run rich so that the engine stays cooler.

4. Prevent overheating:

You should note that overheating your engine is the quickest way to ruin it. It would not only be detrimental to the engine but could also damage the chain, clutch, the guide bar, or melt off the plastic casing. It may also cause the bar oil to evaporate, thus overheating and wearing your chain. I have come across numerous situations where the smoke comes out of brand-new saws running at WOT.

Always make sure that the cooling system isn’t packed with debris and unrestricted air flows through the cylinder. Secondly, never run your saw at WOT when it’s stuck as this can also result in overheating. The added load raises the failure chances of the pistons within your engine.

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