4 Common Stihl Ms 391 problems + Troubleshooting

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Stihl 391 has all the cutting-edge technology to tackle even the most audacious timber-cutting job. It is why it is amongst the most bought chainsaws in the market. 

Unfortunately, many reports have shown that the unit is plagued with several mechanical problems. 

Some of the common Stihl ms 391 problems are starting, carburetor, oil leakages, chain tensioning problems, and fuel system issues. 

And what this article does is it tells you the cause of these problems and recommends a possible solution. 

4 Common Stihl Ms 391 problems

Note: Some users have had the Stihl 391 chainsaw and have yet to experience these problems. 

Anyways, let’s jump straight into it: 

1. Starting Issues

You may have difficulties starting your chainsaw if you have a faulty ignition system, clogged or dirty air filter, carburetor, and fouled spark plug. 

But have you flipped on the ON/OFF or set the ignition switch to the “ON” position before starting the engine? 

Sometimes, we overanalyze the situation, not knowing the problem is right before our nose. 

Take care of the basics first before assuming it is a technical problem. 

If that’s not the case, you can inspect the air filter for clog or wear. 

Clogged air filters restrict proper airflow to the engine, which may hinder starting. So ensure it is clean and still intact. 

A fouled spark plug is another likely culprit that hampers ignition. See if it needs replacement, and act accordingly. 

2. Oil Leakages

Oil leakage is a lubrication system issue. And there are only a few places to look for.

 First is the oil cap or oil filler cap. 

The oil will slip out if there is any visible damage, cracks, or improperly sealed cap. So, ensure the cap is still intact or securely tightened to prevent leaks. 

Secondly, if not replaced, a damaged gasket or O-ring can let oil slide. 

And lastly, a clogged oil tank vent will not allow proper air interaction with the oil. This can create lots of pressure in the tank that results in leakage. 

Hence, it should always be free of debris. 

3. Chain tensioning problems

If the chain is too loose or tight, it will impact your cutting performance. 

Slacked chains won’t cut efficiently. It will keep coming off the bar while in use. 

You must use a wrench to access the tensioning mechanism, turning the screw clockwise to tighten the chain. It should snugly fit but still be able to rotate easily by hand. 

Inspect if you have gotten a proper tension. Pull the chain from the guide and release it. If it snaps back to its original position, all is well. 

You should also recheck the tension occasionally, as the chain stretches in the long run. 

On the other hand, if the chain is too tight, it causes excessive friction that accelerates wear on the bar. You MUST loosen the chain a bit by turning the tension screw counterclockwise.

4. Fuel system issues

Stihl MS 391 chainsaw faulty fuel system can whirlwind loads of problems from 

Starting issues are fuel system-related problems. Whether the engine stalls shortly after starting or it does not fire.  

A surefire way to fix this problem is to fill in fresh and properly mixed fuel (gasoline and 2-cycle oil). The ratio should be within what the user manual recommends.

You must also check if the carburetor, fuel filter, and fuel lines are clogged. Chances are they are. So clean or replace if need be. 

The spark plug is also one to inspect for damage or corrosion. 

Should there be Visible fuel leakage, hold the fuel lines responsible. 

Inspect for cracks or loose fittings and repair them immediately. Aside from that, overfilling the fuel tank or not tightening the seal can result in spills and leakage. 

Frequently Asked Question

How Much Is Stihl Ms 391?

The Stihl 391 price is one thing I can’t really place my finger on. I can’t give you a fixed amount. 

It is usually priced at $600 to $900, depending on your location, certain features and accessories attached, and whether it is a fairly-used model or brand new. 

How Long Does Stihl Fuel Last?

Stihl MotoMix premixed fuel has no ethanol and can last up to two years if sealed and kept in a cool, dry place. 

Although Stihl recommends, it should be used within a short period after purchase –like a few weeks or months. 

What Happens If Chainsaw Runs Out Of Bar Oil?

Your unit will be on the brink of collapse as it experiences tiny wear and tear that could lead to an expensive repair. 

Under no circumstance should you use your chainsaw without bar oil. A lot could go wrong, and none of them are pretty. 

First, your safety isn’t guaranteed. Operating a chainsaw without proper lubrication is unpredictable and could kick back.

Aside from that, it increases friction and heat, which can blunt the chain and potentially damage the bar or chain sprocket. 

Can I Use Car Oil For Chainsaw Bar?

Absolutely not! 

It is no longer a secret people use fresh motor oil in a pinch as a chain oil substitute. 

Some had it good; others didn’t. It can go either way because these are two distinctive oils made for their respective uses. 

Chainsaw oil has special additives to give the chain and bar sufficient adhesion. These additives neutralize overheating, minimize friction, and shield the chain and bar against wear, even at high temperatures.

However, car engine oil helps with internal combustion and does not exhibit the same properties as chainsaw oil. This is where most people got it wrong. 

What Can I Substitute For Bar Oil?

Many people turn to vegetable and motor oil as an alternative to bar oil in an emergency. 

Call it a temporary solution or whatever label that suits your story. It is not ideal. And don’t buy into such a narrative.

 If you run out of bar oil when needed most, drive to the nearest store to get a new one. It is only a stone’s throw away. 

Using bar oil ensures longevity and optimal performance of your chainsaw. 


Despite the Stihl 391’s shortcomings, it doesn’t label it a bad unit.  As I said before, many users have positive experiences with this model. And I’m one of them. 

Although regular maintenance played a significant role in mine, and that is the whole point.  Preemptive strategies trump reactionary responses! 


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