8 Most Common Stihl MS 661 Problems & Troubleshooting

Stihl MS 661 is an excellent option for anyone looking for a professional fuel saw. This chainsaw is backed by unique features that make it a highly recommended choice. For instance, it has M-Tronic technology. The chain is also equipped with an adjustable oiler that operates automatically.

But like the rest of the Stihl chainsaw family, including the Stihl MS 271, some users have experienced a few Stihl ms 661 problems. 

Generally speaking, these problems do not call for replacing the chainsaw, but they could be bothering these users somehow. Most of these problems require proper maintenance, as lack of care can cause engine stalling, insufficient power levels, or idle failure.

If you want to know more about these problems and troubleshooting methods, read for some insight.

The Most Common Problems with Stihl MS 661

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As you already know by now, the perfect chainsaw is non-existent. Each one has its strengths and weaknesses. Still, the Stihl MS 661 has a package of lucrative features and minimal problems. Most of these problems are manageable and easily fixed with proper and regular maintenance.

1. The chainsaw idles erratically

When your chainsaw’s idle is not consistent, the idle speed will rise and fall without your intervention. There could be various issues leading to this condition. There could be something as complicated as an iced-up carburetor or as simple as an improper adjustment.

You can quickly fix this issue if the idle adjustment is not set correctly. All that is required is to turn the low-speed screw counterclockwise. You will not stop until your saw’s engine properly starts and keeps accelerating without lagging.

When you turn the low adjustment screw, keep that in mind to move it slightly. It would help if you turned on the saw to see the outcome of this change. If nothing happens, you will have to keep trying.

If the carburetor is iced up, you can notice that the engine is shaking. This is an issue of insufficient airflow inside the machine. You can open the throttle to let more air in to adjust to this situation.

Also, you will have to let the engine warm up till it reaches 10 degrees Celsius. But make sure to make the warmup process gradual.

2. Insufficient engine power

If the engine power does not seem enough to run efficiently, there can be different culprits. For instance, the fuel level could be too low, which requires refueling the saw. A lack of proper cleaning of engine parts can sometimes result in a loss of power. So, it would be best to search for clogs inside the carburetor. 

Also, an unclean air filter can reduce energy levels. In the case of dirty engine components, you can use a brush and a commercial cleaning product to restore the cleanliness of the filter and the carburetor. But sometimes, cleaning both parts will not be enough. So, getting a replacement and reinstalling them is the best thing.

3. Failure to reach the highest speed

Various causes are preventing the chainsaw from reaching its maximum speed. Sometimes, it could be a problem with one of the machine’s components. There could be a problem with the spark arrestor. This component is what the name says. It keeps sparks trapped inside the machine and makes them unable to leave the saw in the form of exhaust. 

When this component is not clean, the engine will stall or bog down and fail to reach its maximum speed. You won’t need anything other than an old toothbrush to clean the arrestor screen. You can find the arrestor’s screen right behind the chainsaw’s muffler.

4. Crooked cutting

You should expect nothing but efficient and even cuts when you use a versatile chainsaw like Stihl ms 661 or Stihl 500i. When cuts show crooked signs, you can doubt the chain’s teeth. You can blame the usual wear and corrosion for uneven teeth. 

When wear and tear hit some teeth, they will be unequal. To solve this issue, you must regularly sharpen these teeth. You can follow the user manual to have clear instructions regarding proper sharpening.

But if you are unfamiliar with this process, you can seek professional help. It could be unsafe for untrained hands.

5. The engine starts and stops quickly   

This is not one of the most common Stihl MS 661 issues. It happens with various machines, including the Kioti CK3510 tractors. You can identify this issue when the engine runs smoothly and successfully but won’t last more than a few seconds.

In this case, you will need to look at the spark plug. It is the part that is responsible for igniting air and mixing fuel. This mix generates proper power levels that keep the engine operating for the entire cutting time.

Sometimes, the spark plug gets clogged with old gasoline deposits. So, cleaning it thoroughly is what you should do. But if this part is burned or corroded, you should get a replacement.

6. Poor performance

When you get used to the efficient cutting power of your Stihl MS 661, you will notice when the performance is no longer the same. This can indicate a problem in your maintenance routine. In this case, you should inspect the most critical parts of the engine, such as the filters, carburetor, and spark plug.

Whenever there is a torn or damaged component, try to replace it fast to avoid further damage to other parts. Also, maintain inspecting fuel lines and hoses, as they get damaged over time from constant use. Defective parts can lead to leakage and loss of fuel, which makes the performance inefficient.

7. Improper chain alignment

This issue is one of the constantly repeated Stihl ms 661 problems. You can notice this problem when the inclination of the chain looks unaligned. It gets even more apparent when one of the bar’s sides has a deep groove while the other has a shallower one. This issue is pretty simple to handle if you know how to adjust the bar. You have to check the tightness level of the bolts in the bar brackets. This allows you to lift or lower the chain level as per proper adjustment. Doing so will reach the correct alignment, which eventually leads to flawless cuts.

8. Stuck chain brake

A chain brake is an excellent feature responsible for adding to the safety of chainsaws. You will need it to be adequately engaged when starting to use the saw. But if the brake is stuck, it could be due to accumulated debris inside the brake system. Cleaning the chain brakes is a relatively easy task.

All it takes is removing the sprocket cover to get inside the chain’s body. Then you can use compressed air to remove the dirt and debris. When the cleaning is done, you should add a small amount of lubricating oil to the pivot points. Then restore everything to its original shape, and the brake should engage and disengage just fine.

Stihl MS 661 problems: are they a deal breaker?

This chainsaw offers great performance and value despite listing all these typical Stihl ms 661 problems. But you will have to give it some proper care to avoid most of the troubles due to negligence. Also, you must use the manufacturer’s recommended fuel to avoid damaging the engine forever.  

Knowing the capabilities of the chainsaw is a vital point to keep in mind if you want to enjoy its longevity. The chainsaw is made to meet professional forestry needs. It can be a good option for cutting down a large tree when used correctly and with the right bar size.

The power of its engine is 7.2 bhp, and it weighs nearly 7.5 kilograms. So, it is a bit heavy and requires careful carrying and proper maintenance, as lack of care can cause engine stalling, insufficient power levels, or idle failure.

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( Farming Equipment Expert )

Marvin is an expert in farming equipment with a strong background in agricultural engineering. He graduated from Kansas State College of Agriculture, where he received a degree in Agricultural Engineering and specialized in farm equipment design and maintenance.