STIHL Weed Eater How to and Troubleshooting Guide

stihl weed eater how to and troubleshooting guide

With spring and summer around the corner yard, cleanup chores are about to make their way onto the spring to-do list. And one of the most essential tools for yard clean up is a weed cutter. And having been in storage for close to 6 months, some troubleshooting may be necessary if the weed eater is not performing optimally.

And if you happen to own a Stihl weed eater, then you have come to the right place. Keep reading to learn how to fix issues your weed eater may have and how to use it efficiently.

Why is my Stihl weed eater not starting?

If your Stihl trimmer is not starting, the problem is likely related to either the spark, the fuel or the air circulation in the combustion chamber. More often than not, it’s an easy fix, possibly involving the replacement of a spark plug or air filter. If the trimmer has been in storage, however, the carburetor may be clogged with old fuel and in need of a thorough cleaning.

Restricted Air Flow

If the engine sputters but won’t quite turn over, there’s a good chance that the air filter or spark arrestor are clogged. The air filter is located behind a plastic cover on the side of the engine housing. Pull off the cover and pry the filter out with a screwdriver to clean or replace it. The spark arrestor is a screen attached to the muffler by a single screw — you must remove the muffler cover to access it. Replacement screens are inexpensive, but if you prefer to clean the one you have, immerse it overnight in a strong solvent, such as lacquer thinner or acetone.

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Spark Plug Problems

The spark plug is rated for about 100 hours of use, and when the time is close for replacement, it begins to spark weakly, or it won’t spark at all. The plug can also be fouled by deposits collecting in the engine due to a dirty air filter. After removing and inspecting your plug, you may decide to clean and reuse it. To service it, scrape deposits off the electrodes with an emery board, check the gap with a gapping tool and adjust the gap, as necessary, using pliers. The gap should be 0.02 inches.

Fuel Problems

Most Stihl trimmers run on an oil/gas mixture, and failure to add oil to the gas in the ratio specified on the instruction manual can cause the engine to seize. Fuel can also clog the carburetor if you allow the trimmer to stand for an extended period with a full gas tank. Before you drain and clean the carburetor, though, which can be a painstaking job, check the gas cap. If the cap isn’t properly tightened, the fuel delivery system won’t work properly.

Damaged Spark Plug

Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.

Clogged Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Clogged Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance.

This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Faulty Recoil Starter

The recoil starter assembly engages the crankshaft to turn over the engine. If the recoil starter assembly is defective, the engine won’t start. Remove the starter assembly and inspect it to determine if it is working properly.

When you pull the starter rope, tabs extending from the pulley and cam should grab the hub on the engine, causing the engine to turn. When you release the rope, the tabs should retract and the rope should rewind back on the pulley. If the recoil starter assembly is not working, you will need to replace it.

Broken Recoil Starter Pulley

The recoil starter pulley winds up the starter rope when the rope is not in use. If the recoil pulley is broken or stuck, it won’t be able to rewind the starter rope. As a result, the engine won’t start. If the recoil starter pulley is broken, replace it.

Broken Rewind Pulley and Spring

The rewind spring might be broken. When the starter rope is pulled and released, the rewind spring recoils the starter rope onto the rewind pulley. If the rewind spring is broken, the rope won’t be able to recoil onto the pulley.

As a result, the engine won’t start. If the rewind spring is broken, replace it. Many rewind springs can be replaced individually, but it may be easier to replace the whole rewind pulley and spring assembly.

Broken Rewind Springs

When the starter rope is pulled and released, the rewind spring recoils the starter rope onto the rewind pulley. If the rewind spring is broken, the rope won’t be able to recoil onto the pulley. As a result, the engine won’t start. If the rewind spring is broken, replace it. Many rewind springs can be replaced individually, but it may be easier to replace the whole recoil starter assembly.

Clogged Fuel Filter

The fuel filter might be clogged. A clogged fuel filter is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the fuel filter and prevent the engine from starting. If old fuel was left in the string trimmer, drain the old fuel from the fuel tank and replace the fuel filter.

Clogged or broken Spark Arrestor

The spark arrestor is a small screen that prevents the engine from emitting sparks. Over time, the spark arrestor can become clogged with soot. If the spark arrestor is clogged, the engine may not start. To unclog the spark arrestor, remove it and clean it with a wire brush. You may also replace the spark arrestor.

Clogged Air Filter

The air filter may be clogged. If the air filter is clogged, the engine will get too much fuel and not enough air. As a result, the engine may not start. If the air filter is clogged, replace it.

Note: Once you’ve narrowed the problem down to a carburetor issue, it may be wise to bring the trimmer to a Stihl service technician.

Stihl Weed Eater Starting Procedure

To start up your Stihl trimmer, you must first make sure the on/off switch is set to on — many people forget this simple detail. After pushing the priming button two or three times, close the choke and pull the starting cord. The engine should sputter after two or three pulls. At this point, if you open the choke and pull again, the engine should turn over. Be sure to depress the throttle to rev the engine before it dies. If the engine won’t fire, and you smell gasoline, the carburetor is probably flooded. Wait 10 minutes before trying again.

How do you fix a Stihl weed eater that bogs down?

Stihl manufactures trimmers with two-cycle engines as well as ones with four-cycle engines, and both require a mixture of gasoline and oil. One reason why one of these trimmers may die at full throttle is that too much oil is in the gas, which causes poor combustion.

Improper operation, including overuse of the choke, can also be responsible. Poor combustion produces carbon deposits that foul the spark plug and exhaust port, making the problem worse.

Operating Your Trimmer

When cold-starting a Stihl trimmer, you must move the control on the control grip to the “Start” position and turn the choke on by moving the lever to the “Choke” position. The choke restricts air flow to the carburetor, producing a fuel-rich mixture in the combustion chamber.

Once the trimmer starts, move the choke all the way in the opposite direction to open the carburetor and allow air to flow. If you don’t do this, the engine will sputter and die when you open the throttle, because too much fuel is in the combustion chamber to ignite.

Restoring Air Circulation

One of the consequences of operating a Stihl trimmer with the choke on or a fuel mixture that has too much oil is that the engine smokes, which fills the spark arrestor screen with carbon deposits that block air flow. You must clean this screen periodically to prevent the engine from stalling.

It’s just as important to regularly replace the intake air filter or clean it by spraying it with compressed air — if it’s the felt type — or washing it with soapy water, if it’s the foam type. Always close the choke before removing the air filter to keep dirt out of the carburetor.

Fuel Filter and Gas Cap

The trimmer can sputter and stall if it isn’t getting enough fuel, and that can happen simply because the fuel filter is dirty. Fuel filters are inexpensive, and it’s more practical to replace a dirty one than it is to try to clean it.

On most models, it’s in the gas tank or on the cap. While you’re cleaning the filter, try running the trimmer with the cap loosened. If it doesn’t stall, the cap vent hole may be plugged; and if so, you should replace the cap as well as the filter.

Adjusting the Carburetor

The carburetor is factory-adjusted for sea level, and if you use the trimmer at high altitudes, it may not get enough air for proper combustion. Most Stihl trimmer carburetors have adjustment screws for high- and low-speed operation, as well as an idle adjustment. The manufacturer’s recommended adjustment procedure is to screw both the high-speed screw — “H” — and low-speed screw — “L” — clockwise until they seat, then back each off a complete turn. After that, adjust the “H” screw no more than one-quarter turn in either direction. Make the adjustments while the engine is warm.

Check the Engine Condition

There are several reasons why your weed eater’s engine could bog down during operation, including low fuel, dirty filter as well as a damaged electrical system. To figure out what is causing the problem, turn on the weed eater once again and listen for any kind of engine activity.

Fixing a stalled engine that will simply not start will likely require more advanced skill-set than most people have. However, if your engine sputters first before it dies, then it is much easier to fix.

Adjust the Air Filter

As mentioned above, always start with problems that have easy fixes, such as checking your weed eater’s air filter. If the filter is left wide open, then your engine is probably getting excessive air, which leads to choking.

Likewise, the filter can also get clogged up by debris and dirt, which affect proper air flow and thus the engine will stall. So, the key here is to aim for that perfect middle ground by reinstalling the air filter properly or replacing it altogether.

Once you have made the necessary adjustments to the air filter, switch on your weed eater and check whether it is running properly. If you do not get any more problems, either with stalling or choking, then you have successfully fixed the problem.

However, if the device is still not functioning smoothing, then you need to continue the troubleshooting below by checking other problem areas.

Fuel Problems

A common reason for what causes a gas weed eater to bog down is actually insufficient fuel. To check whether this could be the cause for your problem, check the amount of fuel you have in the tank.

If you discover that you have enough fuel but your machine does not start, then examine the fuel tubes. Sometimes the tubing can be damaged or disengaged and this means that your engine is not getting the energy source it needs for proper functioning.

It is generally recommended that you only use fuel that is not more than 3 months old to power your weed eater. This is because old fuel may not move fluidly enough through the engine’s carburetor and thus prevent it from starting.

Also, keep in mind that gasoline and oil usually separate with time and thus you should first shake your fuel mixture before filling your tank. Sometimes numerous attempts to switch on a weed eater can also cause problems. In this case, the engine gets flooded with too much fuel and is therefore unable to start. To fix this problem, simply drain out the excess fuel.

Follow the manufacturer’s guidelines on draining fuel that specific trimmer. Additionally, you may have to repeat that procedure several times until the weed eater starts. Check out additional information on proper fuel use here!

Spark Plug Problems

Even if you are using a clogged air filter or badly mixed fuel, your gas weed eater should still give you some kind of response when you start it up.

However, if you are not even getting a splutter from your engine, then the issue may be with the spark plug. A dirty spark plug is a common issue and it hinders the sparks that help fire up the engine.

Fortunately, this problem can be fixed easily by cleaning the plug using some gasoline and a wire brush. You should also check whether the spark plug has any cracks and replace with a new one if you find that it is damaged. Compared to other parts of a weed eater, replacing spark plugs is usually very inexpensive and does not require a lot of technical knowledge.

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Electrical Problems

Diagnosing an electrical weed eater is also very straightforward since the most likely cause is generally the cause.

Begin by checking whether the extension cord works and is firmly plugged into the right electrical outlet. If the extension cord is faulty, use a different extension cord. It is better to go for a high quality extension cord to prevent future problems.

Additionally, check the circuit breaker or fuse that supports the specific electrical outlet where you have plugged in your weed eater to make sure there is no issue with your electrical power.

Reset the Screws

The low and high screws on the weed eater could also be the culprits that are causing the engine trouble. Ensure that you have properly set them in their right positions.

You can make half turn adjustments in opposite directions to find the best position. Normally, the engine will start functioning once you screw in the correct setting.

Engine Running Rough or Choking

Also consider purchasing a new carburetor kit. Fuel lines and filters can easily get gummed up it the trimmer is left sitting unused for more than a month at a time.

How to change Stihl weed eater string

Having the right trimmer line properly loaded in your STIHL trimmer is essential for safe and optimal performance. Follow these steps guide to learn how to correctly replace the line for your STIHL trimmer.

Before you begin any maintenance on your equipment, make sure the equipment is completely powered off and thoroughly cleaned of dirt and debris.

Items Needed

  1. Trimmer line
  2. Tape measure
  3. Scissors


  • Turn the switch off. If your model is electric, unplug it, and if it’s battery-powered, remove the battery.
  • Turn the trimmer over so the head is facing you.
  • Grasp the base of the head with one hand and put your other hand over the top.
  • Depress one of the tabs on the side with your finger, then rotate the head 180 degrees and depress the other tab.
  • Pull off the cover.
  • Remove the spool.
  • On some models you may have to unscrew a nut in the center of the spool to get it out. You can do this by hand.
  • Pull out the old string, and clean the head and spool with a rag.
  • Cut two lengths of string (any type or diameter that is specified for your model) to the recommended length.
  • An easy way to get two identical lengths is to measure one length that is twice as long as you need, then fold it in half and cut it with scissors.
  • Feed the end of one string into one of the holes in the center of the spool and wind the string tightly around that half of the spool in the direction of the arrow imprinted on the back.
  • When you have about 5 inches remaining, hook the end into one of the notches on the rim.
  • Feed one end of the other string into the hole on the opposite side of the spool and wind the string in the same direction around the other half of the spool.
  • Hook the end into the notch on the opposite side of the rim.
  • Put the spool back into the housing with the notches almost lined up with the two grooves in the rim of the housing.
  • Replace the lock nut, if there is one.
  • Push down on the spool, rotate it until the notches and groove line up, then release the spool. It should stay in place.
  • Feed the strings into the grooves on the housing and pull them out of the notches in the spool.
  • Set the cover on top of the spool, line up the release tabs and push down on the cover. It should lock into place.

How to restring a gas powered weed eater;

  • Turn off the trimmer, and pull the boot off the spark plug to prevent an accidental start-up.
  • Lay the trimmer on a flat surface, and turn it over to access the trimmer head.
  • Remove the cover from the head. If you have an AutoCut or SuperCut head, press the two tabs on the side of the cover while you lift the cover off.
  • If you have a TrimCut head, turn the star nut on the top of the head clockwise to unscrew it—it has reverse threads — and remove the nut.
  • Lift the spool out of the head. If it doesn’t come easily, push down and rotate it 90 degrees counterclockwise to release it.
  • Pull the old string out, and clean off grass and other debris.
  • Cut two equal lengths of new string from a roll, using a tape measure to measure length and scissors to cut the string.
  • Make sure to use the proper-diameter string for your head.
  • Consult your owner’s manual or the Stihl website for the maximum length to cut the string—it varies with trimmer head model.
  • Feed the end of one of the lengths of string into one of the retaining holes in the spool hub.
  • The hub is split, so choose one of the two holes in the section nearest the top of the spool, where the notches in the hub are located.
  • Wind the string in the direction shown by the arrow on the bottom of the spool.
  • When you have 5 inches left, hook the string into one of the notches.
  • Insert the end of the second string in the retaining hole that is opposite the hole you used for the first string.
  • Wind the second string in the same direction, and hook the end in the notch on the opposite side of the spool when 5 inches are left.
  • Replace the spool in the trimmer head.
  • If you have an AutoCut or SuperCut head, line up the notches on the spool with those on the head, then push down on the spool and rotate it slightly counterclockwise to lock it in place.
  • Feed the string through the notches on the head, and snap on the cover.
  • If you have a TrimCut head, feed the strings through the holes in the cover, replace the cover and screw on the star nut.
  • Ensure you turn the nut counterclockwise to tighten it.

NOTE: Not all STIHL trimmer line is compatible with your STIHL trimmer head. Avoid using string with a diameter that is too large for the head. You can damage the head as well as the trimmer.

Please refer to your trimmer head instruction card to determine the correct diameter and length of STIHL trimmer line you will need. If you do not have this card, you can download a digital version online at STIHL Product Instruction Manuals.

How often should you change your Stihl weed eater string?

It is advisable to replace the string at the start of every cutting season as the string tends to get brittle over time and may break and recoil making it difficult to replace. You are better off replacing it before it snaps mid-operation.

How to replace the pull cord on a Stihl weed eater

Items needed

  • Magnet
  • Snap ring pliers
  • Large and small needle-nose pliers
  • Stihl torx/plug socket.

How to Replace a Starter Rope in a Stihl FS 55 Trimmer

The Stihl FS 55 is a straight-shaft trimmer that can be used with any of Stihl’s trimmer heads or cutting attachments. It features widespread handlebars and a shoulder strap, both of which reduce user fatigue when doing extensive brush clearing or lawn trimming.

When the starter rope, which is located on the rear of the engine housing, wears or breaks, the machine won’t work until you replace it. Fortunately, this isn’t a complicated job because the starter housing is easily removable.

Note: The width of the replacement rope must be the same as the existing rope for the starter to operate.

  • Pull the wire off the spark plug to prevent the trimmer from accidentally firing up.
  • Place the trimmer on a flat surface with the engine housing upright.
  • Remove the three screws holding the starter assembly to the engine housing with a Phillips screwdriver.
  • Put the screws in a safe place.
  • Lift the starter assembly off the housing and turn it over to reveal the rotor.
  • Take out what’s left of the old rope.
  • You may need to loosen the knot in the end of the rope with needle-nose pliers to get it out of the rotor hub.
  • Feed the new rope through the hole in the rotor hub, tie a knot in the end and pull on the rope to set the knot inside the hub.
  • If the rope is frayed and doesn’t go through the hole easily, melt the end with a lighter and roll it into a point with your fingers.
  • Hold the rope upright, and use it to wind the rotor clockwise through six or seven revolutions.
  • Keeping tension on the rope, allowing the rotor to unwind while you guide the rope into the groove around the rim.
  • Thread the other end of the rope through the starter cover and through the starter grip.
  • Slide the grip next to the cover, and then tie a knot in the rope to secure it.
  • Cut off the extra rope with a knife.
  • Set the starter back on the engine housing and screw it in place.
  • Replace the spark plug wire before you start the trimmer.

How to Replace the Pull Cord on a Stihl KM 56 RC Trimmer

You will need a plug socket tool with a torx bit on the other end. The weed eater should have come with one when you bought it.


  • Remove the end cover.
  • Remove the snap ring.
  • Disassemble the unit into two pieces.
  • Remove the coil from the shaft.
  • Hold the spring in place after removing the coil.
  • Remove the broken piece of rope.
  • Clean out debris on the cover.
  • Measure out a new piece of rope.
  • Thread the new rope into the coil assembly.
  • Tie a small knot at the end of the rope and pull it into the coil pocket.
  • Wind the pull cord rope around the coil.
  • Reinstall the coil into the housing.
  • Turn the coil two revolutions clockwise to add tension.
  • Thread the rope through the hole in the end cover.
  • Install the handle.
  • Reinstall the end cover.

How to replace the trimmer head attachment

Follow the steps below to replacr your trimmer head attachment:

  • Insert a small screwdriver or nail into a small hole on the head of the trimmer.
  • Then turn it counterclockwise to remove the head, being sure to keep the small disc attached.
  • Insert the new head on the shaft and turn clockwise until you feel tension.
  • Hold the screwdriver or nail in place where you placed it to remove the old head attachment.
  • Continue to turn in order to tighten the head attachment a little more (roughly half a turn).
  • Depending on the model of the head attachment, you may need to pull a few inches of string out before using your trimmer.

Stihl weed eater won’t start when hot

A weed eater engine requires constant air flow to keep operating. If not, it will overheat and ultimately shut down and refuse to power back up. Overheating can be as a result of several issues which as simple to fix without needing to hire a professional. So how do you fix an overheating weed eater?

Restoring Air Circulation

Having good air circulation is perhaps one of the most important parts of the engine process. This air needs to be cool and will mix with the fuel. However, this airflow could be interrupted for a variety of reasons. Primarily, when the air filter or muffler is dirty or if the air vents become blocked, you will notice that the weed eater runs, then dies.

This is because the air cannot properly circulate around the power system and the fuel will be prevented from moving around freely. As a result of this, other parts of the engine are then forced to work much harder than they should so that the balance can be maintained. And since the engine is not designed to work this hard, it will simply shut down.

Check this too: Murray M2500 Weed Eater How to & Troubleshooting Guide

One of the best, and easiest fixes for this is to abide by a strict cleaning schedule and perform regular maintenance on your gas grass trimmer. Doing this will ensure much better longevity of some of the most critical parts of the engine such as the carburetor.

Check Fuel Filter And Gas Cap

Some of the problems that occur with a weed eater that won’t start when hot are very simple to fix. It can be easy to become flustered and assume that the issue is something drastic that needs to be addressed by a professional. But before you book in, you should take a look at some of the most simply parts of your string trimmer.

For example, if the fuel filters are dirty, this could result in improper air flow and an improper fuel supply. Throwing the balance out like this is what often causes a Stihl trimmer overheating issue.

Check the fuel filter and remove any debris or obstructions. Furthermore, you will need to replace the fuel filter from time to time. The frequency of this will depend on how often the trimmer is used. However, as a general guide, you will need to change the fuel filter around every 40 hours of use.

You will also need to check the gas cap. This will give you an indication as to whether the air vent is blocked. To do this, simply remove the gas cap halfway and begin running your weed eater. Doing this will allow any hot air to escape. Of course, you will need to remove any blockages in order to prevent the problem from occurring in the future.

Check The Carburetor

When your Stihl weed eater won’t start, this could be a problem with the diaphragm located in the fuel pump. If this becomes warped, it will no longer operate as expected. As a result of this, the fuel supply will be interrupted and this will prevent the weed whacker from working.

However, this may not be the only issue with the carburetor, there could also be an issue with inlet lever moving out of its correct position. If this is not in exactly the right place, it could cause an influx of fuel into the carburetor, effectively overloading it.

In this case, you may need to seek out a professional to perform a service.

Maintain Fuel Supply

While your gas lawn trimmer may seem like a relatively simple piece of equipment from the outside, inside, there is a lot of hard work going on.

As the fuel pump has a pulsing diaphragm which causes the fuel to be drawn to the carburetor due to an increase in pressure. Of course, if there are things in the way, the fuel is unable to enter the carburetor as easily and this will undoubtedly cause problems. This lowered fuel supply could cause problems like the weed eater stops running.

Make sure that the fuel filter remains unobstructed and that the fuel is able to flow freely. Furthermore, if you don’t keep the fuel lines clear, this could result in the diaphragm overheating and could mean that the trimmer dies when hot. You may also notice that there are air vents that allow any hot air to escape. However, if these are obstructed, the internal parts may overheat.

Check for Leaks

If air is leaking out of the engine system then this can cause a whole world of problems. As we have discovered, it is important to have a stable flow of air and if there is a leak, this causes a significant interruption and will cause the weed eater to overheat.

There may be several places that an air leak could occur, most commonly, you may find them in the fuel tank or the fuel lines. Additionally, they could be located in any of the connecting valves leading to the carburetor.

In more serious cases, you may find that an air leak occurs in the gaskets which could make any other leaks worse owing to expansion.

Engine Operation

There are four cycle engines and two cycle engines although the latter is much more common in residential equipment. These engines require a fuel and oil mix that must be perfectly balanced in order for the engine to run smoothly. This mix provides a sufficient level of lubrication for the engine.

When you pull the start cord on your trimmer, this triggers a reaction whereby the crankshaft begins to rotate causing a piston to create an intake port for the fuel. When the piston moves up, this creates suction which draws the fuel and oil into the carburetor. Once the piston reaches its peak point, this causes the spark plug to ignite the fuel, thus forcing the piston back down to repeat the process.

How to use a brush blade with a Stihl weed eater

While STIHL trimmers are known for their ability to cut weeds and overgrown grass, they can do much more. With optional interchangeable cutting heads, you can turn your STIHL trimmer into a power brush cutting machine.

Pre-Use Checklist

Switch off the engine completely and allow it to cool before refueling.

Check working environment for any hazards.

Keep a safe distance from other people (50 feet or more).

Ensure attachments are mounted correctly and securely.

Adjust the harness and handle(s) to suit your height.

Personal Protective Equipment Checklist

Brush Shield – To help reduce the risk of injury to the head and face, wear a brush shield with built-in hearing protection.

Hearing Protection – To help protect your hearing, wear sound barriers like ear plugs or ear muffs.

Protective Glasses – Protective glasses should be worn under the brush shield as your primary defense against getting wood chips or other particulates in the eyes.

Gloves – To help protect your hands, always wear heavy-duty work gloves made of leather or other wear-resistant material.

Leg Protection – To help protect your legs, wear long pants made of heavy material.

Protective Boots – To help maintain good footing, wear sturdy boots with nonslip soles. Steel-toe safety boots are recommended.

Mounting the Cutting Blade

  • Lay a Stihl weed eater on the ground with the cutting head bottom facing upward. Insert a screwdriver into the hole in the bottom of the gearbox.
  • Hold the screwdriver steady with one hand.
  • Grasp the mowing head with your other hand and turn it clockwise to unscrew it.
  • Lift the mowing head straight up and off the tool.
  • Remove the three screws that hold the mowing head deflector on the gearbox flange.
  • Set the mowing deflector aside and attach the limit-stop deflector using the three screws on the flange.
  • The limit-stop deflector is smaller than the mowing deflector.
  • Set a cutting attachment on the shaft that is pointing up.
  • Circular blades must point clockwise in the direction of the arrow imprinted on the deflector.
  • Three- and four-sided blades may point in either direction.
  • Place the metal washer and thrust plate on the shaft. Insert a screwdriver into the gearbox and hold it in place.
  • Add the mounting nut on top of the thrust plate and tighten it clockwise with the combination wrench included in the package.
  • Pull the cap off the spark plug to keep the trimmer from accidentally starting.
  • Place the Stihl trimmer upside down so you can easily access the black cutter head assembly.
  • Push the locking pin into the side of the cutter shaft, and rotate the cutter head until the locking pin locks in place.
  • Remove the knurled plastic bump-down button from the cutter head assembly by turning it clockwise.
  • Pull the string spool off the shaft.
  • Remove the nut that holds the spool cover onto the shaft with a wrench, and then pull the cover off the shaft.
  • Place the blade shroud onto the trimmer shaft, then place the blade onto the trimmer shaft.
  • Secure the blade and the shroud firmly onto the trimmer shaft with the nut you previously removed. Remove the locking pin from the cutter shaft.

Brushcutter Starting Procedure

  1. Start in a well-ventilated area.
  2. Move at least 10 feet away from your fueling spot.
  3. Press the primer bulb at least 5 times (if unit has a primer bulb).
  4. Use choke if the engine is cold.
  5. Make sure you have secure footing.
  6. Ensure the cutting attachment is not touching anything.
  7. Start your brushcutter.

Basic Technique

Because the cutting attachment rotates counter-clockwise, a right-to-left cutting motion is recommended. The advantage of this method is that the trimmings fall on the cut area.

  • Trimming for Long Grass

When working in very long grass or tough weeds, two passes are recommended. An initial pass, right to left, cuts the top of the grass. Then, a lower pass, left to right, removes the remaining grass. The trimmings will discard to the left.

  • Mowing Large, Flat Areas

The best way to cut large areas is to use the square method. Divide the area to be mown into squares, and then work along the outsides toward the center.

  • Mowing on a Hill – The Strip Method

The strip method is a good way to mow a slope. Cut a strip parallel to the slope, and then return along the swath. Then, cut the next strip above and repeat.

  • Trimming Around Obstacles

The “mowing line” created by the trimmer is the best way of navigating right up to trees or bushes without damaging them. If several plants are growing close together, try to clear around them before mowing. To do that, use the deflector on your brushcutter as a guide. Place the deflector up against the base of the tree or bush and use it to guide you as you move. That protects the trunk while mowing the area around it.

Holding Bike–Handle Brush cutters

When putting on the harness, the spring hook should be about a hand’s width below your right hip. Suspend the machine from the eyelet using the spring hook.

Adjust the handles and push the carrying ring along the shaft until the brush cutter is balanced. The cutting attachment should be just above the ground. The optimum cutting angle is automatically achieved when the machine is balanced.

The correct brush cutter position is with your arms slightly bent and your wrists straight. Please refer to your product’s instruction manual for specific tips on using the circular saw blade.

Holding Loop-Handle Trimmers

First, put on the shoulder strap and attach the hook to the carrying ring on the machine. The hook should be about a hand’s width below your right hip.

Always hold the trimmer / brush cutter with both hands. Your left hand should be on the loop handle and your right hand on the shaft handle.

For more information specific to your model, view the product instruction manual.

How to adjust the carburetor on a Stihl weed eater

Stihl trimmer carburetors are preset at the factory, but it’s common for them to fall out of adjustment after heavy use. When the carburetor isn’t adjusted properly, the engine may smoke, due to fuel/air mixture that’s too rich, or it may race or stall, which is usually because of a lean mixture.

You can adjust the fuel/air mixture using three screws located on the side of the carburetor right between the air filter and the fuel tank. You’ll need a special tool to turn these screws if you have a newer model.

Check this too: Homelite Weed Eater How to & Troubleshooting Guide

The High, Low, and Idle Screws

The three adjustment screws are labeled H for high, L for low and LA for idle. The L screw controls the fuel mixture when the trimmer is operating at low speed, and on a chainsaw, it’s usually the first one you adjust, although following an adjustment sequence isn’t as important for a string trimmer. The H screw controls the mixture when the trimmer is operating at full throttle, and the LA screw adjusts the idle mixture.

Items needed

  • Pliers
  • Flat-head screwdriver
  • Carburetor adjustment tool


  • Set the trimmer on a flat surface with the trimmer head hanging over the edge so it can spin.
  • For safety, it’s a good idea to remove the string spool before you start so no one gets hurt.
  • You do this by holding down the tabs on the spool cover, lifting off the cover and then lifting off the spool.
  • Remove the air filter cover and pull out the air filter.
  • If it’s dirty, clean or replace it, because a dirty filter prevents proper carburetor adjustment.
  • You can leave the filter out while doing the adjustment, but if it’s clean, you can also put it back and replace the cover.
  • Stihl supplies rubber guards on the carburetor screws, and you have to remove them before you can adjust the screws.
  • You can usually pull them off with pliers or pry them off with a flathead screwdriver.
  • Start the trimmer and hold the throttle trigger in all the way to get the trimmer head spinning at maximum speed.
  • Turn the H screw clockwise with a carburetor adjustment tool until the head is spinning as fast as it will go.
  • Then back off the screw carefully until the RPMs start to decrease.
  • Turn the screw slowly clockwise again until the engine once again just starts to pick up speed.
  • Release the throttle and let the trimmer idle. If it stalls, turn the LA screw clockwise until the engine keeps running when the throttle isn’t engaged.
  • The trimmer head may be spinning, but you’ll correct that after adjusting the L screw.
  • With the engine idling, turn the L screw clockwise until the engine speed just starts to increase.
  • Then back it off slowly until you hear the speed just starting to decrease.
  • Leave the screw in this position, because you don’t want a rich mixture at low speed.
  • Turn the LA screw clockwise until the trimmer head just starts to spin, then back off the screw slowly.
  • The point at which the head stops spinning is the optimum position for the idle screw.

Stihl battery operated weed eater won’t start

Before you investigate bigger problems causing your Weed Eater to lose power, make sure the switch is turned to the “on” position. If the trimmer is an electric model, make sure the power cord is plugged in. Check the breaker panel or fuse box powering the outlet. If a breaker has tripped, or a fuse has blown, reset the breaker or replace the fuse.

Battery powered models must have a fully charged battery to power up properly, and gas powered Weed Eater trimmers require a fuel to oil mixture at a 40:1 ratio. Weed Eater recommends mixing 3.2 ounces of two cycle air cooled engine oil with a gallon of regular gas to obtain this ratio.

Once you have ascertained that there is a deeper underlying issue at hand, check to see if the culprit is one of the causes listed below and remedy as needed.

Debris Clogging Line

If you have a battery powered or electric Weed Eater trimmer that won’t start, turn the power switch to the “off” position and check the bottom of the trimmer. If grass or debris has clogged around the trimmer’s cutting line, the trimmer may not start. Clear all material from the underside of the trimmer to resolve the problem.

Dirty Spark Plugs

A dirty spark plug can cause a gas powered trimmer’s engine not to start. Remove the spark plug and clean the electrode with a wire brush. If the spark plug electrode in a gas powered Weed Eater trimmer is covered with gasoline, though, replace it with a new plug.

Spark plugs must have a precise gap to function properly. The gap, which refers to the space between the center and side electrodes of the spark plug, should be set at 1/4 inch.

When To Call a Professional

Battery powered trimmers that don’t start may have a defective power switch, and this must be repaired by a professional. If your trimmer is gas powered, check the fuel lines if troubleshooting doesn’t restore power. If the lines are kinked or split, fuel can’t reach the carburetor, which means the engine can’t be powered.

Straighten kinked fuel lines or contact a professional to replace the lines. Never operate your Weed Eater if the fuel lines are damaged or leaking fuel. Sometimes the trimmer’s carburetor needs readjustment, but this is a repair better left to a professional.

How to recharge a Stihl weed eater battery

Proper handling is the most important factor in ensuring long battery service life. To charge your trimmer’s battery;

Charging to a level of 80% is optimal for normal operation. In the AP 80 battery, this charge state is reached after just 25 minutes with the AL 300 quick charger; with the AL 100 standard charger, it takes 70 minutes.

Once the optimum charge state has been reached, the charger automatically continues to charge the battery with a very low charging current that prolongs battery life until 100% of capacity is reached. Make certain that you operate your charger at temperatures between +5°C and +40°C.

If your battery is too warm, the charging process will only begin once the battery has cooled down. The AL 300 quick charger accelerates cooling with the help of an integrated cooling air system.

General Battery Care Tips

  1. Protect your battery against moisture, humidity, heat, fire and direct sunlight.
  2. Use the battery only at temperatures within a range of -10 °C to +50 °C.
  3. Safeguard your battery against unapproved use (e.g., by children).
  4. To prevent accidental starting of the motor, the battery should be removed from the machine after use.
  5. Use only STIHL chargers to charge your STIHL battery and unplug the power cord afterwards.
  6. Store your battery in a closed, dry space in a secure location.
  7. For optimum service life and low self-discharge, store your battery at temperatures from + 10°C to + 20°C. Ideally, you should store the battery in your basement. There it is generally neither too warm nor too cold.
  8. If you store your battery for a long period, e.g., during the winter, it should be stored with an approx. 30% charge. Charge your battery again just before you use your machine for the first time.
  9. If you have a backup battery, you should not store it unused, but instead alternate its use with your other battery.
  10. Do not open batteries and never use a defective or deformed battery. Defective batteries must be replaced. Please contact your STIHL servicing dealer.

How long do Stihl weed eater batteries last?

The battery life of a Stihl battery depends on the type of battery. But on average Stihl trimmer batteries can last anywhere from 25 minutes to 150 minutes. The FSA 57 trimmer uses the AK10 battery that has a 25-minute running time.

While the FSA 130R uses the AK2000 battery that has an average running time of 50 minutes. At the end of the day, how long the battery lasts depend on the type of the battery and a myriad of other factors. Such as, the area being cleared, the weight of the trimmer, and a

Stihl weed eater primer bulb not filling

Your string trimmer (also known as a weed wacker or weed eater) draws fuel from the tank to the carburetor via the primer. When the primer won’t prime, the engine won’t run.

Primer Bulb and Line

The primer is a small plastic bulb with an attached line that feeds the string trimmer fuel. Pressing the primer a few times before starting will deliver the fuel. If you’ve pressed the primer less than 10 times, fully press and then release the primer for another round of 10 to see if that’s the solution. If not, the bulb may be damaged.

The bulb and line can become clogged or tangled. Check the primer bulb for damage, as cracks or holes can appear in the plastic over time. If the bulb is intact, examine the visible line to ensure it’s not tangled or pulled.

The primer is used for “cold” starts, so if you’re running out of fuel or if the primer is being used after warming up, the carburetor or fuel line may be damaged and in need of service. Primer bulbs that are cracked can be easily and cheaply replaced.

Check Gas Tank and Seals

Is your gas tank properly filled? The contents of the tank shouldn’t be more than 90 days old. Draining and replacing the existing fuel with a mix of fresh fuel and two-cycle oil (one gallon of fuel with three ounces of oil is the rule of thumb) may solve your problem.

The seals around the gas tank need to be examined for damage as well. The gas vent should be open, and the oil and fuel should be mixed. Shake the tool to mix the oil and gas if it has been several days since refilling since the two components can separate. Be careful not to flood the engine.

Check the Carburetor

The carburetor is located near the choke and primer bulb. The air filter or muffler may cover the area. Use a screwdriver to remove the cover to inspect the carburetor. There are two fuel lines that connect to the carburetor. These can become blocked. Gently pull off the two fuel lines using a pair of needle-nose pliers and hold the trimmer upside down.

If no drops are coming out, fuel isn’t reaching the carburetor, and the fuel lines will need to be replaced. If the fuel lines are intact, the carburetor may just need to be cleaned of buildup. If cleaning doesn’t solve the problem, the carburetor may need to be replaced. It’s cheaper to buy a new carburetor than a new string trimmer.

Replace Fuel Lines for Primer

Safely drain all the remaining gas from the trimmer tank into a fuel container. Once it’s empty, use your needle-nose pliers to pull out the fuel line and fuel filter from the engine. A new fuel line and filter can be bought at your local home improvement or hardware store. When purchasing, make sure the replacements fit your brand. Replace both following the instructions on the packaging. When finished, refill the gas tank, reconnect the primer line to the carburetor and press the primer. The gas should flow into the carburetor, allowing you to start the engine.

Cord will not go back on Stihl weed eater

This rope can get stuck simply because it’s tangled, but sometimes the problem is in the starting coil. The spring may be displaced or, if the cord doesn’t retract, it may be broken. Occasionally, the problem is deeper inside the engine. In order to troubleshoot and fix a stuck cord, you have to remove the starter housing. A general procedure works for most string trimmer models.

To remedy the issue;

Items needed

  • Phillips or Torx screwdriver
  • Hammer
  • Flathead screwdriver
  • Thin cord
  • Recoil spring
  • Needlenose pliers


  • Turn off the string trimmer and let it cool down, if it’s been running. Pull the wire off the spark plug.
  • Remove the engine from the trimmer shaft. You need to do this in most models to gain access to the starting mechanism.

Note: The procedure is a little different for each make and model, but it involves unscrewing the screws holding the shaft to the engine and disconnecting the wires. You may need a Phillips or Torx screwdriver, depending on your trimmer model. Don’t forget to disconnect the throttle wire from the carburetor.

  • Unscrew the spark plug and insert a length of thin cord through the empty hole to bind the piston.
  • Then unscrew the single screw holding the clutch drum and remove it.
  • Unscrew and remove the clutch plates. You may have to tap their rims with a hammer and flathead screwdriver to loosen the screws holding them.
  • Disassemble the motor housing by unscrewing the screws holding it together and prying the two halves apart.
  • Turn over the half containing the starter pulley assembly.
  • Access the pulley by removing the cap and the spring underneath it. You can now lift out the pulley and untangle the rope.
  • If the rope isn’t tangled, but it doesn’t retract, you should replace the recoil spring.
  • Lift out the pulley to access it. You should be able to lift out the old spring and drop in a new one.
  • Remove the cord from the pulley and place the pulley back on the spindle and align it so that the spring is underneath the recess in the back.
  • Wind it through six or seven turns, then hold it in place.
  • Feed the starter cord through the hole in the housing with needlenose pliers, tie a knot in the end and seat the knot in the pulley hub.
  • Replace the spring and cap that were on top of the pulley, then gently release the pulley and let it slowly wind up the cord.
  • Screw the housing back together and replace the clutch plates.
  • Swivel each plate until it locks into position and then tighten the screw to hold it.
  • Put the clutch drum back on, tighten the screw to hold it and then remove the rope from the spark plug hole and replace the plug.
  • Reattach the shaft to the motor housing by first connecting the throttle cable and wires and replacing the screws.


  1. Leave some cord hanging out of the spark plug hole when you bind the piston. You’ll need it when the time comes to remove the cord.
  2. Check your manual before beginning; some procedures may be slightly different. In particular, the recoil spring may be under tension. If so, you should take the unit to a qualified repair person.

Stihl weed eater FS 40 will not stay running

The two-cycle engine that runs your string trimmer needs three things to operate smoothly: clean fuel, air circulation and a spark. The engine won’t start if any of these elements are missing, but it may run for a short time if only the air or fuel flow is restricted. It isn’t difficult to restore air circulation, but if the fuel flow is restricted, you may need to disassemble the carburetor and clean it.

Air Circulation

The engine draws air into the combustion chamber through the intake port, and if the air filter is dirty, combustion is partial and the trimmer will sputter and die. The air filter is readily removable, and replacements are inexpensive.

Air must exit through the exhaust port, and that is covered by a spark arrestor to prevent fires. When the spark arrestor is clogged, the engine can’t get rid of its exhaust gases, and it won’t keep running. The spark arrestor is a screen located just behind the muffler. Pull it out and clean or replace it.

Fuel Circulation

The gas cap on most trimmer has a small air inlet hole that allows air to enter the fuel tank, preventing a vacuum from forming as fuel sprays into the carburetor. It’s easy to check whether or not this hole is blocked — just loosen the cap and see if the trimmer operation improves. If it does, it’s time to replace the gas cap. The fuel system also includes a filter that can clog. It’s difficult to determine visually whether or not it’s blocked, but it’s easy and inexpensive to replace. You should do this as part of regular maintenance.

Old Fuel

If you leave the trimmer full of gas when you store it for the winter, the fuel partially evaporates, leaving behind a sludge that resembles varnish. This sludge can partially block the inlet ports for the carburetor. Consequently, there may be enough fuel in the carburetor to start the engine, but there may not be enough to keep it running. You can prevent this from happening by adding fuel stabilizer to the gas tank before you store the trimmer, but once the carburetor is blocked, there’s no alternative to cleaning or replacing it.

Carburetor Issues

While it can be a delicate task to disassemble a carburetor for a complete cleaning, you usually don’t have to do that to remove deposits from old fuel. The first step, after you’ve located the carburetor, is to drain the float bowl. After unscrewing and removing it from the trimmer, spray it generously with carburetor cleaner, being sure to direct the cleaner through all the port orifices. If the trimmer doesn’t run smoothly after doing this, disassemble for a more thorough cleaning. It’s probably best to take the carburetor to a service professional for this.

Other reasons why the trimmer won’t stay running include;

Clogged Spark Arrestor

The spark arrestor is a small screen that prevents the engine from emitting sparks. Over time, the spark arrestor can become clogged with soot. If the spark arrestor is clogged, the engine may stall. To unclog the spark arrestor, remove it and clean it with a wire brush. You may also replace the spark arrestor.

Clogged Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to stall. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Clogged Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to stall. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Clogged Fuel Filter

The fuel filter might be clogged. A clogged fuel filter is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the fuel filter and cause the engine to stall. If old fuel was left in the string trimmer, drain the old fuel from the fuel tank and replace the fuel filter.

Clogged Air Filter

The air filter may be clogged. If the air filter is clogged, the engine will get too much fuel and not enough air. As a result, the engine may stall. If the air filter is clogged, replace it.

Stihl weed eater running but head not spinning

Below are some reasons why your trimmer is not spinning despite the fact that the motor is running;

Worn out Clutch

The clutch engages one or more drive shafts which attach to the trimmer head. If the clutch assembly is worn out, it won’t be able to engage the drive shafts to rotate the trimmer head. You may be able to clean and repair the clutch assembly. However, since replacing the clutch is relatively easy and inexpensive, it may be easier to replace the clutch assembly.

Broken Drive Shaft

The drive shaft is a long, flexible shaft which connects the clutch to the trimmer head. The drive shaft engages the trimmer head. If the drive shaft is broken, the string trimmer head won’t spin. The drive shaft is not repairable—if the drive shaft is broken, you must replace it.

Worn out Trimmer Head

If the threads on the drive shaft are stripped, the trimmer head will not stay on the shaft. If this happens, replace both the trimmer head and the drive shaft.

Broken Throttle Cable

The throttle cable connects the throttle trigger to the carburetor. When the cable is pulled, it opens the throttle on the carburetor to accelerate the engine. If the throttle cable is broken, the engine will not accelerate, and the trimmer head won’t spin. If the throttle cable is broken, replace it.

Check this too: Echo Weed Eater How-to and Troubleshooting Guide

How to Replace a Broken Shaft on a Stihl Line Trimmer

The trimmer’s can wear out after many hours of service, and you’ll need to replace it. The main symptoms of a broken shaft are noise, vibrations in the drive tube and a head that spins intermittently or not at all. A bad clutch can also cause some of these symptoms, but if an examination of the flexible shaft reveals that it has turned blue, the shaft is faulty.

To replace the shaft;

  • Access the shaft by pulling it out from the end of the trimmer’s drive tube.
  • To do this, you need to remove the cutting head.
  • Start by removing the spark plug wire, and then lay the tool on a table or other flat surface.
  • Turn the cutting head until the hole behind the deflector lines up with the one in the thrust plate and you can push a locking pin through them.
  • If you don’t have the locking pin that came with the trimmer, use a 1/4-inch hex wrench instead.
  • This prevents the shaft from turning, so you can remove the head.
  • Unscrew the head or the retaining nut that holds the head counterclockwise to remove it.
  • Once the head is off, you can remove the locking pin.
  • Remove the thrust plate by pulling it off.
  • Release the clamp on the deflector, and pull the deflector off the shaft.
  • Release the clamp holding the gear housing to the shaft, and loosen the fixing screw with a screwdriver to pull off the gear housing and expose the end of the flexible shaft.
  • Grasp the flexible shaft with adjustable pliers and pull it out of the drive tube.
  • Coat the new shaft with lubricating grease and insert it into the drive tube.
  • Push it until it stops, and then use the pliers to rotate it until it locks into the clutch and you can push it still more.
  • When the shaft is fully seated in the clutch, only 0.6 inches should extend beyond the end of the drive tube.
  • Slide on the gear housing; clamp it and tighten the fixing screw.
  • Replace the deflector and clamp it, and slide on the thrust plate.
  • Insert the locking pin to block the shaft. Then screw on the cutting head, turning it clockwise to tighten it.

How to clean and maintain your Stihl weed eater

Here are some tips to apply in order to clean your weed eater:

Disconnecting the Power Source

Weed eaters are powered by electricity, batteries, or gasoline. Before you start cleaning, it is necessary to remove the power source.

If your weed eater is powered by electricity, then you should unplug it from the electric outlet.

If it is powered with a battery, remove the battery.

If you are using a gasoline powered weed eater, then you should empty the tank, especially if you are moving the tool to store after cleaning it. But if you are not moving the tool into storage, you may leave the fuel in the tank. Just ensure that you switch off the machine before you begin cleaning.

Removing Dirt

Normally, after trimming the weeds and grass in your lawn there will be some debris, dust and cut grasses left on your weed eater. If you leave it all on the machine, the collection may cake up and make an even worse mess later on.

  • Start your cleaning first by brushing of the dirt and debris, weeds and particles of grasses.
  • Use a stiff brush to do it so that it will be able to remove caked debris.
  • Maintain a back and forth movement with the brush over stubborn debris and particles so that they will loosen and be removed.
  • If the debris and particles are resistant and require additional force in order to be removed then you should bring a small amount of soapy, warm water for dipping the brush.
  • The main parts that you should brush and scrub with warm soapy water are the handles and deck of your gardening tool.
  • Ensure the trimmer is completely dry before storing it. Do not store it while is is still wet.  Doing so can cause it to get damaged or rusty.

Clean the Spark Arrestor

After using your machine for a total of 25 hours, it is time to clean your spark arrestor. It’s normally cleaned with carbon cleaner and a wire brush. Return it back after cleaning.

Clean the Spark Plug

This only applies to gasoline weed eaters;

  • Use a socket wrench to remove the spark plug.
  • Use a brake cleaner to remove dirt and debris from the head of the spark plug.
  • Check the tip of the spark plug; if it is black, then it is time to replace it. If it is not black, then you can put it back.

How to clean and maintain your trimmer’s air filter:

After using your machine for a collective total of 10 hours, it is time to wash the filter. The filter is covered and so you have to first remove the cover in order to wash the filter with soapy water. Use clean water to rinse the filter after washing it. Then air-dry it and apply motor oil on it before putting it back in its place. Remember to cover it again with the cover.

A question that frequently comes up is how often should you clean your air filter on your STHIL trimmer. You should always clean it after 10 hours of use and stick to that time interval. Follow these steps to clean and maintain the air filter, while also checking the fuel mixture and pull cord while you are at it:

  • Take off the side cover by loosening the bolts.
  • Check for dirt and debris that has built up around the air filter before taking it out so that does not fall into the air filter.
  • Use a nylon brush to clean the air filter. “Do not use compressed air as it can separate the fleece and allow contaminants to escape through the air filter.” – Cody
  • Check the fuel mixture – Make sure you are using 89 octane or better and HomCo’s HP ultra full synthetic two stroke motor mix.
  • When filling up fuel, clean dirt and debris around the fuel cap so it doesn’t fall in your tank when you open it. If you have been running your unit in the field and it has warmed up, open the fuel cap slowly so it can vent, then take the cap off.
  • Make sure your pull cord is not frayed or split, or showing any signs it will break. Pull it all the way out and inspect it while you are doing this basic maintenance.

Clean the Muffler

If you notice your weed eater losing power when you use it, you may have a problem with carbon buildup on the muffler. This problem has become less common, as Stihl continues to improve both their trimmer design and the burning quality of their oil, which is known for its ability to burn clean and leave little, if any, residue on the machine. However, if you’ve used the wrong type of oil, or if you’ve put too much oil into your Stihl machine, you may encounter some carbon buildup on your muffler. It’s a sticky black residue, but fortunately, getting it off isn’t a complicated process.

  • Turn the engine off and let it cool completely before handling any part of the muffler or engine on the Stihl trimmer.
  • Set the Stihl equipment on hard, level ground, so that the right side (on your right when you are using the trimmer) is up and the left side is on the ground.
  • Locate the muffler. In all Stihl trimmers manufactured in 2000 or after, the muffler will be on that right side, which is facing up.
  • If you notice your weed eater losing power when you use it, you may have a problem with carbon buildup on the muffler.
  • Remove the screws holding the muffler and shielding in place with a screwdriver.
  • There will either be two or four T-27 Torx screws, which are star-shaped, depending on which model you have.
  • Remove any shielding. In newer models, the entire mufflers will slide off of the machine for easy cleaning.
  • Remove the screen inside the muffler. It may be pressed into place or may have a threaded screw holding it into place.
  • If the screen is excessively dirty or worn, remove it.
  • Remove the screws holding the muffler and shielding in place with a screwdriver.
  • Soak the muffler in a heavy-duty degreaser for about two hours. Remove the muffler and rinse well.
  • Dry the muffler off with a shop rag or paper towel before putting in a new screen.
  • Put the muffler back in place and tighten down the screws.
  • Reconnect the Power Source
  • When you have cleaned the weed eater and you want to use it, reconnect the original power source.
  • If you are moving it into storage, you may remove the battery and keep it somewhere safe or else empty the gasoline from the fuel tank.

Maintaining your Stihl Weed eater

String trimmers can make a big difference in the level of difficulty in your yard care regimen. They’re able to get in small spaces and around objects such as trees, fence lines and bed edges — places mowers often miss or are too large to get to. Stihl trimmers are rather inexpensive when compared to other outdoor power equipment, and string trimmers require regular maintenance to keep running properly.

Regular Maintenance

If you have a Stihl trimmer that won’t start when hot, the best solution to this problem is to perform regular maintenance on your equipment. Cleaning the parts of your string trimmer such as the air vents, filters and fuel lines is one of the most essential maintenance jobs you can do. However, there are other important things to stay on top of:

Regularly replace parts including filters, trimmer line and the spark plug.

Inspect parts for damage on a regular basis; be sure to turn off the trimmer and remove the spark plug when doing this to avoid accidental start ups.

You should make sure that the idle speed is always correct. If you find that the trimmer stalls when idle, this may solve the problem. However, since you can only adjust this with the spark plug installed, you must wear protective gear.

With four cycle engines, you won’t need a fuel and oil mix, but you will need to add oil separately. This should be kept topped up.

When not in use, ensure that you store your weed eater in a dry, well-ventilated area.

Pre-Storage Maintenance

Prior to storing gas-powered outdoor equipment, you have to perform maintenance procedures which will allow for safe storage. Stihl specifically recommends draining and cleaning the fuel tank, and running the engine until the carburetor is dry to prevent the diaphragms from sticking together.

During this time, remove the trimmer head and clean it thoroughly, inspecting for any damage. Clean the machine thoroughly, removing any grass and debris. Stihl recommends paying special attention to the cylinder fins and air filter.

Check this too: Worx Leaf Blower How to & Troubleshooting Guide

In addition, you may want to consider adding a fuel stabilizer to the trimmer’s fuel and running the engine to distribute the fuel throughout the fuel lines and carburetor. This can help prevent buildup during storage. Add oil to the cylinder and slowly pull the starter cord to distribute oil to the moving parts.

Pre-Season Maintenance

After storing during the winter months, a few maintenance procedures will ensure your trimmer is ready for the season. Replace the cutting line at the start of the season as many trimmer lines can become brittle with age. Replace the spark plug prior to the cutting season, as well. Check over the trimmer for signs of damage or debris that may have occurred during storage.

Cutting Season Maintenance

While pre-storage and pre-season maintenance procedures are annual, your Stihl trimmer also needs maintenance throughout the cutting season at various intervals. For example, Stihl recommends the following during every refueling stop: checking the idle adjustment, checking the tightness of the cutting head and checking the control handle’s operation. Replace the spark plug after every 100 hours of use. Every 12 months, replace the pickup in the fuel tank.

Other Maintenance

During the cutting season, your trimmer may show signs of damage or have parts that need to be inspected, cleaned or replaced. These include the air filter, fuel tank, spark plug and cooling inlets. If you notice your trimmer’s engine seems low on power, it may be the spark arresting screen located in the muffler of the machine. For this problem, Stihl recommends having servicing or repair work completed by an authorized Stihl servicing dealer.