How Important Is A Decompression Valve In A Chainsaw?

A decompression valve releases the compression in the starting procedure from the combustion chamber, thereby making the engine easier to turn and pull the recoil rope. 

The decompression valve is the main feature highlighting the safety of a chainsaw.

It is a crucial component in initiating the function of a chainsaw.

How important is a decompression valve in a chainsaw

Importance of a decompression valve in a chainsaw

The decompression valve is a crucial feature focusing on the safety of using a chainsaw.

As the operator pulls the starter cord, the piston recoils the resistance, making it tough to start the chainsaw for the operator.

It is at this point that the decompression valve plays a vital part.

The chamber of the decompression expels considerable compression, making it easier for the smooth starting of the chainsaw without any sudden kickbacks.

As the starter cord pulls the decompression valve, it opens by manual force and automatically closes with the release of the cord by the operator.

The chainsaws mostly come in two decompression valve types and feature a slight difference in operation, structure, and design.

  • Automatic– Many chainsaw suppliers and operators choose self-activated decompression valves even if the engine is inactive. It is because as the operator starts the chainsaw engine, the decompression valve closes automatically, until the time the operator stops the engine.
  • Manual– The decompression valves that are designed manually are triggered as the operator pulls the cord of the starter to ignite the unit. It is the moment after the starting of the engine, and it restores the decompression valve in a closed state.

The decompression value has equal importance to the other components of the chainsaw. It also needs good maintenance regularly.

Occasionally, the parts need checking. Look if the valve has dust, debris, or grime.

Give proper inspection and check the spark plug as it triggers within the decompression chamber the ignition.

The decompression valve system is a part fitted with an engine with all the Stihl chainsaws.

It is a part of the chainsaw helping in starting the engine.

It extends the opening times of the valve while starting. Thus, the engines enjoy convenient starting.

What causes much compression on chainsaws?

The chainsaw has many working parts and determining the actual cause of a chainsaw is to check and undergo many trials and errors.

Many gasoline-powered yard tools, use two-cycle combustion engines.

The working of the engine starts by driving the piston up and down.

With the first stroke, vacuum pressure is created on the piston’s bottom side, and it sucks fuel in the top.

In the second stroke, fuel is ignited and it pushes from the top of the exhaust.

The vacuum pressure measure is the compression, and it is ideal for the process to operate properly. 


The normal readings of compression are between 90 and 110 psi for any two-cycle engine.

Ensure a tight fit between the chainsaw and the gauge.

However, get an accurate reading to fulfill the need for pressure while starting an engine.

Bad Old Fuel

The compression problems relate to fuel largely.

Bad or old fuel cause lots of trouble in the yard pieces of equipment.

It is best to drain the gasoline mixture that is in balance in the gas tank and to include fresh oil before using it.

If it fails to resolve the issue, it may be due to excessive fuel in the gas filters and gas lines.

The lines may be running to the carburetor from the tank and are back.

However, if the chainsaw model features a primer bulb externally, it may have a line extra between the carburetor and the bulb.

Thus, the fuel filter stays connected to any of the end lines within the tank.

It requires replacing the old parts with new parts approved by the manufacturer.

Getting a Spark

A common high compression cause is due to bad spark plug. However, this repair is easy to try at home.

You need to remove the chainsaw cover to see the spark plug .

You may uncap the plug and using a ratchet unscrew it.

Replace the same with a new plug and replace the cover and the cap.

How is decompression helpful in release work?

The release mechanism of the compression works to comfort the internal combustion engines starting.

It allows spinning up the starting speed, and there is no need to work against the pistons pumping action.

The simplest way of checking for a low compression in a chainsaw is to keep the chainsaw on the ground and lift it using the starter rope.

Good compression will not allow the rope to pull out.

However, you must be careful while lifting the chainsaw weight using the starting cord.

Compression Tips for Chainsaws

Checking Levels of compression- If there is any suspicion of low compression, you must best go for further specific test needs.

Determining the compression is important to understand if it is getting lost.

The gauge of compression works like the gauge of a tire, it reads the pressure within the engine.

The compression gauge hooks through the spark plug hole to the cylinder.

Pull on the starter rope for the compression to give a max reading.

Most chainsaws operate with compression readings well and it ranges from 100 to 160 psi.

How to go about:

  • On checking the starter assembly function, the operator gets to move to determine if the compression is increasing or dropping.
  • A quick test on compression helps determine if the source is compression or something else.

The operator needs to tell if there are problems due to compression, and it is necessary, as compression repairs are difficult.

Problems with compression take place due to air leaks within the internal engine, around the crankshaft seals and gaskets.

As the decompression valve in a chainsaw is important, having cracked or broken parts will require disassembling the entire engine before the problems are solved.

You must take the chainsaw to a professional in case you doubt these repairs are possible at home; remember improper repairs may ruin an engine.

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