The key component to smoothly starting your Stihl chainsaw is the spark plug. Unfortunately, this device is also to blame if your saw doesn’t start. Sounds odd, doesn’t it?

You see, the plug has a center electrode and a ground electrode. If the distance between them is not accurate, the spark plug will not start the chainsaw; rather it will cause misfires. Hence, it is vital to ensure a precise spark plug gap.

When it comes to chainsaws made by Stihl, the optimal spark plug gap is 0.020. In terms of the remaining chainsaws, the gap ranges between 0.020 to 0.030.

stihl chainsaw spark plug gap

I will begin the article by explaining why spark plug gaps matter. I will also explain how to measure your Stihl chainsaw gap and set it correctly.

Let’s kick things off!

Chainsaw Spark Plug Gap: What Is It?

Before I discuss the gap, let me explain the spark plug. It is a device located inside an internal combustion engine’s cylinder head. The item is designed to ignite the mixture of air and fuel. But how?

What Is Chainsaw Spark Plug Gap
What Is Chainsaw Spark Plug Gap

The spark plug does so by creating an electrical spark in the combustion chamber, which ignites the fuel. It then lowers the pistons and eventually starts the engine.

As for the spark plug gap, it defines how far apart the center electrode and ground electrode are on the spark plug. This gap is directly correlated with the efficiency of spark ignition.

In other words, if the gap is too broad or too narrow, the engine can’t run well or even won’t start. An incorrect spark plug gap can also pose a fire hazard.

When Should Spark Plug Gaps Be Checked?

As long as your Stihl chainsaw runs smoothly, the gap is set just right. However, there are some issues you will constantly encounter when the gap is incorrect. Let’s take a look at those.

When Should Spark Plug Gaps Be Checked
When Spark Plug Gaps Be Checked

  1. Engine Won’t Start or Has Trouble Starting

Whenever someone asks me why their saw won’t start, I suggest checking the spark plug before anything else.

It is sometimes necessary to replace the spark plug altogether. However, it may not always be the case. There are instances when the spark plug is fully functional, but the gap is causing the machine not to start.

  1. Engine Running Rough or Misfiring

If the spark plug gap is off, it may lead to a rough engine running or misfiring. This is because the spark is not strong enough to ignite the mixture of air and fuel properly.

  1. Engine Having Trouble Reaching Maximum Power Output

The wrong spark plug gap can also prevent your chainsaw from reaching its maximum power output. This can lead to slower cutting and reduced efficiency.

  1. Constantly Losing Power

If your Stihl chainsaw experiences a continuous loss of power, it is a good idea to check the spark plug gap. A properly adjusted gap can prevent this issue from occurring and ensure maximum runtime.

  1. Losing Efficiency in Fuel Consumption

In addition to causing power loss, incorrect spark plug gaps can lead to decreased fuel efficiency. This means more frequent refueling and increased operating costs.

  1. Engine Overheating

It is crucial to understand that the combustion is never complete if the plug gap is improper. This may lead to overheating and even pre-ignition or detonation.

If you want to avoid irreversible engine damage, ensure the overheating is under control as fast as possible.

  1. Experiencing Premature Wear of Spark Plugs and Engine Components

Incorrect spark plug gaps can also cause excessive wear on the spark plug and other engine components, leading to the need for more frequent maintenance and potentially costly repairs.

Leaving the spark plug gap faulty for a long period of time can cause damage to the engine and potentially lead to failure. Thus, it is crucial that the gap is regularly checked and adjusted as necessary.

Also Know: How Tight Should A Chainsaw Chain Be?

How to Measure the Spark Plug Gap on Stihl Chainsaws?

If you have experienced any of the above problems, your chainsaw’s spark plug gap is likely faulty. However, to fix the gap, you must figure out what the gap measures. Here’s how to go about it:

Measuring Spark Plug Gap on Stihl Chainsaws
Step by Step Measuring Spark Plug Gap on Stihl Chainsaws

STEP – 1: Insert the Wire Looms

Place the wire looms in the spark plug gap.

STEP – 2: Checking the Gap

When the looms are inserted, observe carefully whether the gap is adjusted to the looms by 0.020 measurements.

STEP – 3: Identifying the Gap Accuracy

If the gap and the looms match perfectly, your spark plug gap is accurate.

Nevertheless, sometimes the looms will not fit into the gap due to a tight fit. The looms may also be slack and slip through the gaps. Both of these scenarios have to do with incorrect gap settings.

How to Adjust the Spark Plug Gap on Stihl Chainsaws?

In case you discover that the gap is wrong, you must adjust it accordingly. It is fairly easy to adjust the spark plug gap on Stihl chainsaws.

You will need a feeler gauge, which is available at most hardware and auto parts stores. Once you have it, proceed as follows:

Adjust the Spark Plug Gap on Stihl Chainsaws
Adjust the Spark Plug Gap on Stihl Chainsaws: Step by Step

STEP – 1: Cleaning the Plug

Remove the spark plug from the engine and clean it thoroughly with a wire brush to remove any debris or buildup.

STEP – 2: Verifying the Plug’s Functionality

Ensure that the spark plug is working. An easy way to do so is to use a spark plug tester. It gives you a quick overview of the device’s condition.

STEP – 3: Adjust the Plug

Place the spark plug between the V-shaped edges of the feeler gauge and adjust it until you feel resistance. This resistance should indicate that the gap is set correctly.

STEP – 4: Bending the Electrode

If necessary, use pliers to gently bend either the center electrode or ground electrode to adjust the gap as needed until proper resistance is achieved. Be careful not to bend too much, as spark plugs can become damaged in this way.

STEP – 5: Reconnect the Spark Plug

Reinstall the spark plug and test the saw to ensure it is running smoothly.

Depending on the Stihl saw model, the method of checking and adjusting the gap may differ. Therefore, make sure you read the owner’s manual carefully.

In case you aren’t sure what the right gaps for Stihl chainsaws are, move on to the next section.

Stihl Chainsaw Spark Plug Chart

Wouldn’t it be great if you could find the correct gap from one Stihl spark plug gap chart?

This is precisely why I compiled a chart below showing the proper gap for every Stihl chainsaw. The table not only informs you of the gap but also what spark plugs Stihl saws use.

Stihl Chainsaw Model Optimal Gap NGK Spark Plug Torch Spark Plug Champion Spark Plug Bosch Spark Plug
Includes the 06, 07, 07S, as well as the 08, and 08H 0.020 BP6HS/130-272  
The rest of Stihl’s chainsaws 0.020 BPMR7A/130-898 L6RTC/131-051 RCJ6Y/130-073 WS-

Additional Guide to Stihl Spark Plug Gaps

Please refer to the following guide if you did not find the right gap for your Stihl chainsaw on the previous chart. I have included some of the most popular Stihl saws with their correct spark plug gaps below.

Stihl Chainsaw Model Spark Plug Gap
STIHL MS180C 0.5mm (0.02in)
STIHL MS290 0.020
STIHL MS170 0.020
STIHL TS400 00.30 to 00.40 mm

Tips on Setting the Spark Plug Gap

The tips provided below will help beginners and experts set the spark plug gap on Stihl chainsaws effectively.

Tips on Setting the Spark Plug Gap
Quick Tips on Setting the Spark Plug Gap

#Tips 01

The market is full of tools for setting spark plug gaps. Choose whichever is cheap and convenient for you.

However, if you are new to these tools, you should use either wire looms or feeler gauges.

#Tips 02

As a beginner, you should pay special attention to the spark plug adjustment. Remember that even the smallest gaps can significantly impact inexpensive saws.

#Tips 03

While adjusting the gap, make sure the spark plug is not loose. It should always be held by strong support.

#Tips 04

In the event that the gap is too small, you can simply adjust it with a hammer.

This method is only applicable to those who are not beginners. First-timers may damage the electrodes if they use the hammer improperly.

#Tips 05

To enhance the gap, I always recommend the use of wire looms or similar wire-style tools. The process is more complicated with coin-style tools, and the results are only somewhat reliable.

Moreover, a coin-style tool sometimes breaks the spark plug tips. You can no longer use the product with a broken tip.

The Dangers of Excessively Gapped Spark Plugs

Your chainsaw could suffer from a number of major problems if the spark plug gap is too large. Let’s see some of them below.

Excessively Gapped Spark Plugs
Excessively Gapped Spark Plugs

  1. Start-up Failure

The spark plug may not fire properly, preventing the engine from starting. Even when you somehow manage to start it, the saw may not operate smoothly.

  1. Ignition Damage

Excessive gaps can also cause misfires and potential damage to the ignition system. It can amplify vibrations when you use the power tool.

  1. Quick Wear and Tear

An overly wide gap damages the spark plug due to too much voltage being applied. Moreover, the gap may also cause the spark to jump from the electrode to the side of the spark plug, causing damage or erosion.

Both of these will result in the plug wearing out much faster than it should.

  1. Increased Emissions and Poor Fuel Economy

The engine can also consume more fuel and emit more emissions when the gaps are too wide. Having to deal with these issues can be costly and damaging to the environment.

  1. Unsatisfactory Performance

If the spark plug gap is too great, the spark weakens or misfires. This can lead to engine performance issues, such as reduced power output.

Also Read: The Best Chainsaw Safety Gear To Ensure Your Safety

What Happens If a Spark Plug Gap Is Too Small?

I have already stated that a chainsaw should not have a wide spark plug gap. Conversely, the gap should not be too narrow either. Here’s why:

Spark Plug Gap Is Too Small
If Spark Plug Gap Is Too Small: What Will Happens?

  1. Misfire

The short gap will cause the cylinder to misfire frequently. As a result, you will constantly hear popping and knocking sounds.

  1. Weak Spark

A narrow spark plug gap is likely to produce a weak spark. Thus, the spark will not be strong enough to ignite your chainsaw.

  1. Rough Idle

Sometimes a chainsaw won’t stop spinning or creeping forward. The saw may behave like this even when it is not in use, which is quite surprising.

The primary culprit for this rough idle is a small plug gap.

Which Spark Plugs Work Best With Stihl Chainsaws?

When your Stihl saw fails to operate despite adjusting the gap, it is probably time to replace the spark plug.

You should never install a random spark plug since Stihl chainsaws perform best with Bosch and NGK spark plugs. Here are two of the finest spark plugs with their features from these reputable brands:

Best Stihl Chainsaws Spark Plugs
Here Are the 2 Best Spark Plugs for Stihl Chainsaws

>> Bosch 7547 (WSR6F) Spark Plug <<

  • Double platinum surfaces for extended life
  • Yttrium-enhanced ground electrodes for increased durability and performance
  • Nickel alloy center electrode for improved corrosion resistance and spark energy

>> NGK (6703) BPMR7A Spark Plug <<

  • Nickel center electrode for improved corrosion resistance and spark energy
  • Solid copper core for better heat transfer and spark energy
  • Trivalent metal plating for improved anti-seizing and corrosion resistance

Frequently Asked Questions

What Should the Spark Plug Gap Be on a Stihl Chainsaw?

The spark plug gap for most Stihl chainsaw units should be 0.020 inches. However, be sure to check your instruction manual before altering anything.

What Is the Spark Plug Gap on a Stihl Ms 271 Chainsaw?

The spark plug gap of the Stihl 271 chainsaw is 0.020 inches (0.5 mm).

What Size Spark Plug Does a Stihl MS 250 Take?

The Stihl MS 250 uses the NGK BPMR7A plug. This corresponds to a 14 mm thread diameter and a 9.5 mm reach. Its spanner size is 19 mm.

What Spark Plug Does a Stihl Ms310 Take?

The Stihl MS310 fits an NGK BPMR7A plug which measures 14 mm in thread diameter, 9.5 mm in reach, and 7 degrees in heat range. Alternatively, the BOSCH WSR6F can also be used for this model.

What Is an Acceptable Gap for a Spark Plug?

If your engine is between 28-32 cc, set the gap to 0.020 inches. On the other side, 0.025 inches would be a good gap for engines with a displacement of 38-55 cc.

How Often Should Stihl Chainsaw Spark Plugs Be Replaced?

It is advisable to replace your Stihl chainsaw’s spark plug every season or after approximately 100 hours of use. Nonetheless, always follow the instructions in your owner’s manual. Also, inspect and clean spark plugs periodically to prolong their life.

Do Spark Plug Gaps Extend with Time?

No, spark plug gaps usually do not extend with time. Having said that, it may decrease over time due to electrode wear or carbon buildup. This is why inspecting and adjusting the spark plug gap regularly is essential.

Do Spark Plug Gaps Have to Be Exact?

Spark plug gaps should be set accurately, but it does not have to be exact. As long as it falls within the recommended range for your specific engine and spark plug, you should be fine.

What Happens If You Put the Wrong Gap Spark Plugs?

A spark plug with the wrong gap will contribute to poor engine performance, inefficient fuel use, and possible engine damage.

To Sum Up

Setting the correct spark plug gap on your Stihl chainsaw ensures proper engine performance and prevents misfires.

When in doubt, consult your user’s manual to determine the specific gap width and make use of the appropriate tools, such as wire looms or feeler gauges.

Also, don’t forget to change your spark plug every season or every hundred hours of operation, and never use your favorite Stihl saw with improperly gapped spark plugs.

Following these guidelines will keep your chainsaw running like a charm. Happy sawing!

Planning to cut firewood but struggling to find the right chainsaw? Here’s a list of what I consider to be the best firewood saws on the market.

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