How to Unflood a Chainsaw- Expert Advice


Before we can answer the question of how to unflood a chainsaw we first need to address what flooded means. A flooded engine is an engine that has an excessively rich fuel mixture in the cylinder that can not detonate when the spark plug ignites. Flooding is usually caused by operator error from excessively choking the chainsaw, bad fuel, clogged air filter, or a fouled spark plug.

10 Steps to Unflooding a Chainsaw

  1. Place Chainsaw on flat stable surface
  2. Remove Spark Plug
  3. Remove Air Filter
  4. Set Choke to Off and Pull Starter Rope 20 Times
  5. Dry or Replace Spark Plug and Reinstall
  6. Clean or Replace Air Filter and Reinstall
  7. Engage Chainbrake
  8. Start Chainsaw According to Owners Manual
  9. Release Chainbrake
  10. Run Chainsaw Until Unit No Longer Smokes Before Turning Off

Place Chainsaw On a Flat Stable Surface

The first step is to place the chainsaw on a flat stable surface to perform the unflooding procedure.

Remove Spark Plug

The chainsaw’s spark plug will need to be removed from the engine in order to remove excess fuel from the cylinder. Most chainsaws require the operator to remove a top cover to expose the spark plug. Once the cover is removed you will need a chainsaw wrench or a deep socket size 19mm (3/4″) to remove the spark plug.

Remove Air Filter

The air filter will need to be removed next. The air filter is located adjacent to the spark plug under the top cover you removed in the last step. The air filter is normally, depending on your chainsaw’s model number, held in place by snap clips or screws and is very easy to remove.

Set Choke to Off and Pull Starter Rope 20 Times

Now that we have the spark plug and air filter removed from the chainsaw we can now purge the excess fuel from the cylinder. Be sure to wear safety glasses before going further as there is a risk of getting fuel in your eyes in this step.

The starter rope will need to be pulled at least 20 times to help push out the excess fuel. Pulling the starter rope will be easier than normal due to the spark plug not being installed in the chainsaw. Each time the starter rope is pulled fuel will be purged from the engine through the spark plug hole.

Dry or Replace Spark Plug and Reinstall

With the excess fuel removed from the chainsaw’s engine, we need to turn our attention to the spark plug. The spark plug will more than likely be wet with gasoline and will need to be cleaned or dried.

In some cases, the spark plug could be fouled and will need to be replaced. Now that we have either cleaned the spark plug or purchased a new one the spark plug needs to be installed back into the chainsaw’s engine.

Clean or Replace Air Filter and Reinstall

The air filter that was removed earlier will more than likely be dirty or damp with fuel. If this is the case the air filter may be able to be cleaned by gently tapping the filter on a hard surface and blowing lightly with compressed air.

Be mindful not to overdo the compressed air as you can damage the air filter’s material, effectively ruining it. In some cases, the air filter will not be able to be cleaned and will need to be replaced.

Once the air filter is cleaned or a suitable replacement purchased, reinstall the air filter on the chainsaw.

Engage Chainbrake

Now that the saw has been cleared of excess fuel from the engine and the spark plug and air filter have been reinstalled the chainsaw will need to be started.

Before starting the chainsaw the chainsaw’s chain brake will need to be engaged. Always engage a chainsaw’s chain brake before starting a chainsaw.

Start Chainsaw According to Owners Manual

After the chain brake has been engaged it is time to start the chainsaw. Depending on your chainsaw’s model the starting procedure can vary greatly. Be sure to refer to your chainsaw’s owner/operator’s manual for the correct starting process. If the correct starting procedure is not followed correctly the chainsaw may become flooded again and the unflooding process will need to be started from step one again.

Release Chainbrake

Now that the chainsaw is running the chain brake needs to be released.

Run Chainsaw Until Unit No Longer Smokes Before Turning Off

After releasing the chain brake the chainsaw will need to be run until the unit no longer smokes. The smoke coming from the chainsaw’s muffler is being caused by excess fuel that was trapped in the engine’s cylinder. Once the engine has burned the excess fuel, the smoking will stop.

Congratualations! Your chainsaw is no longer flooded.

What Causes a Chainsaw to Flood?

Chainsaw’s get flooded from time to time. Flooding is annoying to deal with but its easily remedied by following the 10 Steps to Unflooding a Chainsaw listed above.

What causes a chainsaw to flood?

A chainsaw can become flooded from operator error of improperly choking the chainsaw, bad or decayed fuel, clogged air filter or a fouled spark plug.

Can Flooding a Chainsaw Damage the Engine?

A flooded chainsaw can be incredibly annoying but can it damage the chainsaw’s engine?

Flooding a chainsaw will not damage the engine of the chainsaw. However, the spark plug and air filter may need to be replaced in the process of clearing the chainsaw of excess fuel.

How Do You Dry Out a Flooded Chainsaw?

When a chainsaw is flooded the cylinder of the chainsaw has to much fuel and can not detonate properly when the spark plug fires.

How do you clear the excess fuel from the engine of the chainsaw?

Clearing fuel from a chainsaw’s cylinder is done be removing the spark plug and pulling the recoil starter 20 times to force the excess fuel from the cylinder. Once the cylinder is clear of excess fuel make sure the spark plug is dry and reinstall back into the chainsaw.

How Long Does it Take to Start a Flooded Saw?

Flooding a chainsaw can happen in a matter of seconds. However, how long does it take to start a chainsaw once its been flooded?

Starting a flooded chainsaw can usually be done in 5 minutes or less by removing the spark plug and purging the excess fuel from the cylinder. Once the engines cylinder clear of excess fuel and the spark plug is dry the chainsaw can be started.

How To Unflood a Stihl Chainsaw

Stihl Chainsaws are known to have a very specific starting procedure that must be followed in order to not flood the chainsaw. If you did not follow the procedure and your chainsaw will not start it is more than likely flooded.

How do you unflood a Stihl Chainsaw? Unflooding a Stihl Chainsaw is as simple as unflooding any other brand of chainsaw.

To unflood a Stihl Chainsaw simply remove and dry the spark plug, purge the engine’s cylinder of excess fuel and reinstall the spark plug. The chainsaw should now be unflooded and ready to start.

Wrapping Up

When your needing to get work done and you have a chainsaw that wont start it can be extremely frustrating. If the reason your chainsaw is not starting is because its flooded you can easily fix the situation.

The 10 Steps to Unfloodng a Chainsaw can be completed in 5 minutes or less and you will be back in business.

Remember to take your time when starting your chainsaw and follow the proper starting process for your chainsaw to avoid flooding it. Also make sure your chainsaw is filled with fresh fuel, clean air filter and good spark plug to avoid flooding your chainsaw again.

With a little care you can avoid flooding your chainsaw. If you accidentally flood your chainsaw its not the end of the world. The worst case scenario is you may lose a little time and need to buy a new spark plug, air filter and fresh fuel.

Have a great day and happy cutting!

Steven R

I have been part of the chainsaw and outdoor power equipment business in one way or the other for over 35 years. There are not many things that I have not seen in the business. From repairs, sales, equipment operation, and safety I can help you with your questions.

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