sithl weed eater won't run at full throttle

Stihl Weed Eater Dies At Full Throttle – SOLVED

It can be hugely frustrating to get out into the garden, prepared to work, only to find that your Stihl weed eater keeps dying. But quite often, the cause of the problem can be easily solved. If your Stihl weed eater won’t run at full throttle, you’re in the right place.

weed eater won't run at full throttle When you turn on your trimmer, you may find that it stays idling perfectly well without any issues. However, when it comes to giving it some gas, the weed eater bogs down. More often than not, this is usually a problem relating to a lack of fuel or air; or both, reaching the engine.

But this may still leave you scratching your head and wondering why your weed eater won’t run at full throttle. The good news is that by following the path of the fuel, you will likely run into the issue and be able to solve it at home.

However, it is important for us to point out that the Stihl string trimmer troubleshooting we will be looking at in this article relates to when a Stihl weed eater won’t run at full throttle and not to when the weed eater won’t run at all.

Stihl String Trimmer Troubleshooting; Dies At Full Throttle

While you may feel disheartened when you encounter Stihl weed eater problems, there are some important things to check before declaring that your weed wacker has had it! Let’s take a look at some of the most common issues and how they can be rectified.

1. Restoring Air Circulation

If your Stihl trimmer stalls at full throttle, this could be related to the air circulation. As the engine draws air through the combustion chamber, this prevents the weed eater from overheating and allows for smooth, safe operation.

However, there are many instances where this airflow could become interrupted and this would result in the trimmer stalling. Most commonly, this is because the air filter is dirty or blocked with debris, preventing air from moving through it. When this happens, your trimmer will splutter and eventually cut out altogether.

But don’t panic; these air filters are very inexpensive and easy to replace. This is something you can do at home. However, if you try this and still encounter problems, it could be that the airflow has been interrupted elsewhere in the system.

2. Check Gas Cap And Fuel Filter

One of the first things you should do when trying to diagnose a problem with your weed eater is to look at the fuel circulation. Of course, you must make sure that there is sufficient fuel in the system and while this may seem like an obvious thing to point out, you’d be surprised how many people forget to check this simple issue before moving on to other things.

Once you’re satisfied that the fuel level is adequate, you may want to check that the inlet hole for air is not obstructed. You will find this on the gas cap and it is present on almost all weed eaters. This air inlet is designed to stop a vacuum forming as the fuel moves into the carburetor, when it is blocked, this is no longer possible.

Locate the gas cap and unscrew it slightly at the same time as running the trimmer. If the weed eater’s operation improves when you do this, it signifies that the gas cap may need to be replaced.

In addition to this, the Stihl weed wacker fuel filter could be causing a problem. This filter can get blocked in the same way as the air filter and gas cap and while it is difficult to tell just by looking, this part is easy to remove and replace. To get the best performance out of your weed eater, you should make this part of your trimmer maintenance.

3. Adjust The Carburetor

Sthil carburetor problems can often be avoided by not storing the weed eater when it is filled with gas. You can add a fuel stabiliser if you intend to store the weed wacker over the winter but if you don’t, this can cause blockages to develop.

The reason for this is that as the fuel sits in the tank for longer periods of time, it will begin to slowly evaporate. This leaves a thick residue behind that can block the fuel filter. While it may look as though there is sufficient fuel in the tank when you come to use it, it may not be enough. The problem is that a block carburetor may have to be replaced or at the very least, cleaned before the trimmer will start working properly again.

There may be times that you need to completely take the carburetor apart and this can be a laborious and delicate job. However, for the most part, this isn’t necessary and you may be able to clean it without having to do this. Removing fuel residue usually requires you to drain the float bowl before taking it out and giving it a good clean with carburetor cleaner. When you do this, you must make sure to get all areas including the port orifices.

In the main, this should solve your problems and the trimmer should begin to run correctly once again. However, in the event that it doesn’t, you may need to take it to a professional who will service the carburetor.

The carburetor is an important part of a gas engine that ensures the fuel and oil work effectively together to start the engine. However, servicing it can be something of a nightmare and is what may put a lot of people off using gas-powered trimmers. That being said, having a better understanding of its maintenance can help. If you are sure that the part isn’t clogged, it could be that one of the following is the issue.

The Idle Speed

When you come to take the carburetor apart to service the idle speed, you will only need a screwdriver, which is great news for people who are feeling a little nervous about attempting this task. However, we would also advise investing in a carburetor rebuilding kit as well.

Begin by testing the current idle speed. Because your weed eater engine is shutting off when you start it, it could be that the idle speed is not fast enough. You will see that there is a screw that allows you to adjust the idle speed located, usually, behind the air filter. However, if you are unsure where to find it, then you can take a look at your user manual.

It is important not to get carried away when making adjustments and you should turn the screw by one quarter at a time, then start the trimmer and test it again. At this point, if the weed eater starts without an issue, you can continue using it. However, if the engine makes a lot of noise when starting up, this could signal deeper problems with the carburetor and it will require taking apart to investigate.

The Diaphragm

The diaphragm is located on one side of the carburetor and is made from plastic. This is a small component that has flaps; these could be the root of your problem. In this case, it could be that the flaps are damaged. Most commonly, it will be that they have worn down or are bent. Replacing them is very simple and most user manuals will have details on how to do this

The Metering Diaphragm

If the diaphragm is not the problem then you may wish to investigate the opposite side of the carburetor where the metering diaphragm is located. There will be a set of screws that can be undone, allowing you to look at the condition of this part.

The metering diaphragm is another small part that resembles a piece of cotton. It is used to regulate the speed of the engine, however, owing to its thin consistency, it can quickly wear out. At times, it may be worn completely through, whereas at other times, it may only be a little worn. In any case, it is a good idea to replace it.

4. Clogged Exhaust

Earlier, we talked about airflow which is essential to the smooth operation of your string trimmer. While a lot of problems may be down to a blocked air filter, it may also be that the exhaust is dirty or blocked.

It is vital that air is able to exit through the exhaust. This part of the trimmer has an arrestor cover which acts as a fire preventer. However, it is not uncommon for this to become clogged with debris. If this happens, the air has nowhere to escape and so the weed wacker will die.

You will find the arrester at the back of the muffler. It is a screen which can be easily taken out and cleaned. If it is really bad, you may need to replace it entirely but once again, this is relatively inexpensive and easy to do.

4. Seek A Professional

If you have been through our troubleshooting checklist and still find that your problems persist, it may be that there is a more significant issue. In this case, you will be left with no other choice but to take your weed eater to the repair shop and seek professional help.

The repairs person will be able to take a thorough look over your equipment and diagnose and problems as well as performing a service and any repairs. Even for simpler problems, professional help can be invaluable for those who are unsure of how to address the issue. It is far more preferable to admit defeat and have your trimmer professionally serviced than to attempt to fix the problem yourself and potentially cause more damage.

Regular Maintenance

Gas engines are delicate and they require a lot of upkeep to ensure that they run to the best of their ability at all times. However, this shouldn’t be something that puts you off using this type of powerful equipment. It is simply a matter of ensuring that you perform regular maintenance.

Let’s take a look at what you need to do and how to clean the air filter on a Stihl weed eater.

Keeping your equipment clean is one of the best ways to ensure that it will always work properly. The air filter is one of the parts that may become clogged with dirt but cleaning it is not a challenging task. Simply remove the air filter and use a soft brush or cloth to dust off any dirt and debris. Alternatively, you can wash the filter in warm soapy water but be sure to allow it to fully dry before putting it back into the trimmer. Furthermore, you should never use compressed air to clean the filter.

Other maintenance that must be completed on a regular basis includes the following;

  • Ensure that the fuel tank does not have any leaks.
  • Make sure that the fuel tank is full, using an ethanol-free gas.
  • Clean any removable parts including the fuel filter and arrestor. Furthermore, you should wipe off any dirt and grass from the exterior parts after each use.
  • Clear any debris from the exhaust.
  • Perform seasonal checks on the various engine system parts such as the spark plug and carb, changing when necessary.


Running a weed eater can come with problems, one of the most common is that the weed eater won’t run at full throttle. While this can be frustrating, there is often a simple solution that you can do yourself at home.

Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.

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