stihl chainsaw how to and troubleshooting guide
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Stihl Chainsaw Troubleshooting & How-to Guide

Stihl is a leading manufacturer of chainsaws and other handheld outdoor and landscaping power tools. The Stihl chainsaw comes with a sturdy body, strong teeth, and a smooth rotating bar to help you cut through trees, ice, and even concrete with ease and precision.

When it comes to power tools, good maintenance, and proper use will maintain the functionality and lifespan of the tool regardless of whether it is an electric miter saw or a gas power chainsaw. It is typical for the Stihl chainsaw to develop some issues, and when this happens, some basic troubleshooting will help identify the source of the issue and solution to help it run smoothly. This article will help you fix the most commonly reported problems of a Stihl chainsaw.

What do you do if your Stihl chainsaw won’t start?

  • Most times, when the Stihl chainsaw stops working, it is never a complete breakdown. You can follow the steps on how to troubleshoot and revive it when it won’t start.
  • Check the saw’s exterior for loose bolts, nuts, and screws and tighten them with an adjustable wrench or screwdriver. The vibration of the tool during use can run some fasteners loose, preventing it from starting again.
  • Use a brush and cloth to clean and remove any dirt, mud, or debris that can interfere with the controls—clean around the chain brake lever, the air filter housing, and the filter. Wash the dirty filter with a non-abrasive detergent and water. Rinse the filter and allow it to air dry before reinstalling it.
  • Check the chainsaw’s fuel if you have not used the tool for a while. Drain and discard the old fuel, mix new fuel and cycle oil in the ratio 50:1 in a container, shake it and then pour the mixture into the chainsaw’s fuel tank.
  • Refill the chain oil by opening the cap on the chain oil tank, filling up the tank until the level is below the cap threads, and then replace the lid. The chain oil will keep the chain lubricated, keep off dirt and allow smooth movement. Use recommedend chain oil lubricant. Don’t substitute it with the garage door lube you have lying around.
  • Check the spark plug of the chain saw if the engine is not starting at all. Remove the spark plug with a spark plug wrench and clean it with a brush to remove carbon scoring and dirt. Check for any cracks and damages and replace if necessary. Check the electrode gap of the spark plug and ensure it is 0.02 inches. Always change the spark plug after 100 operating hours of the chainsaw to avoid engine problems.
  • Check the chain tension and adjust it if it is too loose or tight. Use an adjustable wrench to loosen the two nuts on both sides of the chainsaw. Hold the tip of the blade and adjust the tension of the chain correctly. Make sure it is snug but can also move freely by hand.
  • Check the choke of the chainsaw’s engine and make sure it is completely closed. When you are doing a cold start, push the choke lever to the warm start when the engine starts to run. The choke should be closed during a cold start to limit the air and increase the fuel in the engine to keep it running while it warms up.
  • If the chainsaw won’t stay running when the engine is idle, adjust the carburetor. Find the low speed, high speed, and idle speed screws near the carburetor, start the engine and allow it to warm up. If the chainsaw engine dies when you release the throttle, turn the low-speed screw with a screwdriver clockwise until it stops and then turns it counterclockwise once. Turn the idle speed clockwise until the saw idles and chain turns, and then make a one-fourth counterclockwise turn.

Stihl chainsaw won’t start after refueling.

If you refuel your chainsaw and it still won,t start, below are some of the possible causes and solutions that will get the chainsaw functioning again.

1. Bad fuel

If you recently refueled your Stihl chainsaw, stale gas can be a reason why it won’t start. Every time you fuel the chainsaw, you should make sure to drain the old fuel first to avoid contaminating the new fuel. You should also make sure the new gas you use is appropriate for the chainsaw.  

Stihl recommends using 89 octane gasoline without ethanol, and the gas should not contain more than 10% ethanol. Most fuels nowadays are a blend of ethanol which attracts moisture and speeds up the rotting process. Gas with ethanol also burns hotter than gasoline which can cause the engine to overheat and burn the plug electrodes.

2. Defective spark plug

The spark plug is located in the engine and ignites the fuel and air mixture, driving the piston and running the engine. If the spark plug is too corroded or the electrode is faulty, it cannot create an electrical current to start the system. Disconnect the spark plug from the engine and inspect if it is damaged, eroded, or dirty. If it is too damaged, you should replace it. If it looks physically fine after cleaning it and you haven’t changed it in a few seasons, you should still replace it.

3. Clogged carburetor

The carburetor is a significant part of the chainsaw. It works when cold-starting the engine, when the engine is idle and when the engine is open. The carburetor’s work in a chainsaw engine allows the right amount of fuel and air mixture into the combustion chamber. When the fuel starts to turn stale, it gums up and clogs the carburetor just as it would in an unused lawnmower.

A clogged carburetor won’t allow fuel into the engine, preventing it from starting. You can unclog the carburetor if the clog is minor. To clean it, drain the fuel, spray some carburetor cleaner and loosen the residue with a small brush. If repeated cleaning does not fully unclog the carburetor, you will have to replace it.

4. Defective recoil starter

The recoil starter in a chainsaw is a start mechanism that allows you to pull the rope. It uncoils, tightens the spring, engages the clutch to start the engine. If any of these components are worn or broken, the chain saw won’t start even with fuel. To test the recoil starter, remove it and reposition the spring. If the chainsaw still won’t start, it is defective and requires a replacement.

5. Broken ignition coil

The ignition coil transmits electricity to the spark plug to create a spark that ignites the engine. If the coil is faulty, there will be no spark to start the engine and run the chainsaw. Remove the ignition coil, test it using a multimeter or an ignition coil tester, and confirm your chainsaw model’s resistance specification. If the reading is below or above the required range, then your ignition coil requires changing. Most Stihl chainsaws have a resistance of 0.2-3.0 ohm on the primary coil and 5-20 kiloohm on the secondary coil but always confirm the correct reading for your model number.

6. A flooded engine

A flooded engine is when there is too much gas in the combustion chamber, usually due to repeatedly starting the chainsaw using the recoil system without the engine starting. When there is too much fuel, it will not ignite, and the engine won’t start. Flooding usually happens due to an underlying issue: a bad spark plug, bad gas, or a faulty carburetor. Other than damaged parts, using the choke position to start a warm saw often causes a flooded engine.

A clear sign that you may have a chainsaw engine is when you smell gas while starting it. To fix this problem, turn off the chain saw and let it sit for about 30 minutes to allow the excess gas to evaporate. We have explained the most effective way to unflood a chainsaw engine below.

How to fix a flooded Stihl chainsaw

The purpose of a choke in a chainsaw is to make cold starting more effortless, but if you do not use it properly. If you could start an engine with the choke closed and not turn off the choke on time, you will end up flooding the engine with too much gas. Follow the steps below on how to fix a flooded chainsaw engine.

  • Activate the chain brake and then place the chainsaw on a flat, leveled surface.
  • Open the spark plug hole facing away from you, remove the wire from the spark plug and disconnect the spark plug using a spark plug wrench.
  • Wipe off the excess fuel from the spark plug with a clean rag.
  • Turn off the choke by pressing the control lever to activate the fast idle.
  • Turn the On switch.
  • Hold the saw firmly to the ground and crank the engine about four to six times to bleed out the fuel from the combustion chamber.
  • Insert the air filter and the spark plug, reconnect the spark plug wire, and close the opening.
  • With the choke engaged, pull the starting rope several times again, and the chain saw should start on the third pull. When the motor warms up after about a minute, turn on the choke position.

Alternatively;

  • Remove the air filter.
  • Pour starting fluid into the carburetor and crank the engine several times. Starting fluid will make the fuel more combustible and makes the process of clearing out the combustion chamber much quicker.

To avoid flooding the chainsaw when cold starting, turn the control lever to half choke after the fourth pull and then turn the lever again to the open choke position immediately when the engine starts. It prevents the carburetor from allowing too much fuel into the combustion chamber.

Stihl chainsaw won’t start; it has spark and fuel

When your Stihl chainsaw doesn’t start after changing the spark plug and fuel, some common problems to look for can help diagnose the source of the issue.

Spark plug problems.

Even with new spark plugs in, incorrectly removing and installing the spark plugs can prevent the engine from starting. Other than that, you should also use the correct spark plugs for your chainsaw. Additionally, most spark plugs come pre-gapped. However, you still have to confirm the size of the gap before installing. A smaller gap will cause a weak spark and poor ignition of the engine, while a wider gap will not bring out any spark. Confirm the spark plug gap, check and adjust with a feeler gauge or gaping tool.

Fuel intake problems

If the spark plug is working correctly and you have good fuel, there still has to be enough fuel in the combustion chamber for the engine to start correctly. When you start your chainsaw, the crankshaft spins, creating vacuum pressure on the carburetor, pulling the gas from the tank and into the combustion chamber where it mixes with air and ignites.

If anything prevents the right amount of fuel into the combustion chamber, the chainsaw won’t start. Check for dirty fuel tanks, clogged fuel filters, loose pipes, clogged air filters, and a dirty carburetor, which can all the fuel volume going into the combustion chamber. Clean any mildly dirty parts and replace all the damaged parts.

ProTip: You can use a small air compressor to blow air through the air filter and get rid of the loose dust before proceeding to clean it further

Carburetor problems

The carburetor sucks fuel from the tank, mixes it with the right amount of air, and pushes the mixture into the combustion chamber. If any part of a carburetor has issues, the right amount of fuel/air mixture won’t pump into the chamber, therefore, preventing the engine from starting.

Check for clogged shafts and jets, clogged carburetor, damaged valves, stuck levers, and damaged or warped diaphragms, all of which can interfere with the fueling process. Remove the entire carburetor and clean it. If it has damaged parts, replace it with a carburetor kit that fits your chainsaw model.

Compression problems

The Stihl chainsaw is a two-stroke gas-powered tool that uses a substantial amount of compression to pull fuel from the tank, mix it with air and ignite it to produce energy that runs the chainsaw. If the compression is too high or too low, the engine won’t start. The ideal pressure range of the Stihl chainsaw is between 90 and 110 psi. Compression problems are usually due to an air leak in the engine, usually around the gaskets and seals of the crankshaft. If you suspect a compression issue, seek professional help as compression repairs can be complicated.

Why does the chain keep coming off my Stihl chainsaw?

It is usual for the chainsaw chains to come off with continued use, but there is usually an underlying cause when it’s too repetitive. Below are the reasons the chain keeps coming loose and how to fix it.

1. Damaged guide bar

The chainsaw has grooves all around the outer edge of the guide bar, and the chain has teeth that run within the bar rail to keep the chain in place and moving straight. To inspect the guide bar, disassemble the chain cover, chain and bar. Wipe off any dirt and debris and check for any signs of damages. If the rails are shallow, you need to replace them. Check the chain oiler and ensure it is functional. Check for broken teeth on the chain and replace them if necessary. Ensure the chain fits snugly inside of the bar and the teeth that keep it in place are not worn down too low.

2. Worn out bar heel

As the guide bar wears down with use, the bar heel- the part of the bar nearest to the drive sprocket- also wears down, which increases the distance the chain travels as the bar grooves become less effective. This increased distance will cause the chain to keep coming out of the guiding bar with the vibrating saw.

3. Poor chain tension

For the chainsaw to function appropriately, you must maintain the proper amount of tension on the chain. A very loose chain will cause the blades to come out of the bar, while a very tight chain is also not ideal for the proper functioning of the chainsaw. The correct tension of the chainsaw chain should be slightly loose on the guide bar but tight enough that you can’t pull the drive links out of the bar to fix the chain tension issues; follow the steps below.

  • Use a screw wrench to loosen the nuts on the guide bar side panel to give you room to adjust the chain.
  • Locate the tension adjustment screws to the side of the chainsaw guide bar.
  • Tighten the tension screw with a screwdriver to tighten the chain around the bar. Make sure it fits snug.
  • Lift the bar’s nose and tighten the nuts on the sidebar to secure the sidebar and guide bar in place.

Why does my chainsaw start and then stop?

Several reasons can cause your Stihl chainsaw to bog down when your pull the trigger. It can be from something as simple as starting the chainsaw wrongly to more severe issues like a damaged carburetor. Below we have discussed the most common reasons why your chainsaw won’t idle and the best way to fix it.

1. Wrong starting process

The Stihl chainsaw uses a four-position lever ignition system called the master control lever. The choke position is the fourth setting on the master control lever. When starting the motor when it’s col, you should engage the choke position to increase fuel intake and reduce air to allow the engine to start. When the engine starts running, turn the choke off. If your chainsaw doesn’t automatically turn it off or you forget, the engine cuts off immediately.

2. Blocked air filters

External air goes into the engine through the air filter to cool down the chainsaw engine and also mix with the fuel to ignite and run the saw. Dust particles in the air mix with the lubricating oil and clog up the air filter, therefore, preventing sufficient air from getting into the engine. When there is no air for the spark to ignite, the chainsaw will start and then die after a short while. Remove the air filter, wash it with detergent and water and scrub off the dirt with a brush. If the air filter is too clogged, you should replace it.

3. Dirty fuel filters

Fuel filters trap dirt and contaminants from the fuel to prevent them from damaging the engine. Over time or when using the wrong fuel, the fuel filter becomes too clogged and restricts fuel flow, killing the engine shortly after starting. Replace the fuel filters instead of cleaning them as they are pretty affordable and easy to install too.

4. Clogged spark arrestor

The spark arrestor in a chainsaw traps exhaust products emitted from an internal combustion engine. Over time, soot from the engine clogs up the spark arrestor causing the chainsaw to stall. Uninstall the spark arrestor and unblock it using a brush, but you can also replace it for efficiency.

5. Clogged carburetor

As a result of using bad fuel or leaving fuel in the chainsaw for a long time, the fuel evaporates and leaves behind a sticky substance that accumulates and clogged the carburetor. You can clean and mildly clogged carburetor but if it is too severe, replace it with one compatible with your chainsaw model.

6. Defective spark plugs

A faulty spark plug will have carbon, dirt, and oil blocking the insulator nose, preventing it from firing consistently. Check the spark plug and replace it if needed.

How to troubleshoot a Stihl chainsaw with no spark

A problem in the ignition system is likely to be the culprit when the chainsaw doesn’t spark. The ignition system is responsible for igniting the fuel and air mixture to produce energy that powers the chainsaw. A chainsaw with no spark will shut down suddenly or not start at all. Here is how to troubleshoot a malfunctioning spark plug.

  • Locate the spark plug from the top of the engine underneath the chain brake handle.
  • Remove the air filter cover and then slide off the rubber spark plug connector from the spark plug.
  • Unscrew the spark plug wrench using a spark plug from the engine.
  • Replace the spark plug with a new identical. Make sure the gap is according to the specifications of your chainsaw’s engine.
  • Disengage the chain brake, turn on the ignition switch and install the new spark plug into the rubber connector.
  • Wear rubber gloves and hold the rubber plug and spark plug about 1-2cm from the metal surface of the engine unit.
  • Wipe off any flammable fluid from the metal surface of the engine with a clean rag.
  • Pull the starter rope and look for a blue spark between the electrode of the spark plug.
  • Ensure the wires leading to the On/Off switch are not tangled or in contact with the metal part of the engine if there is no spark. Check if the wires are damaged or broken and replace them if necessary.

How to troubleshoot a Stihl chainsaw with no oiler

When you start the chainsaw, it triggers the worm drive to engage the oiler to send oil through a port that releases onto the bar. As the chain moves over the bar, it spreads the oil across the moving parts to reduce friction and heat. When the oil pimp or oiler is faulty, it will reduce the chainsaw’s performance and power.

1. Clean the oil ports.

Check for clogging around the bar oil. Change in temperatures and dirt will cause clogging anywhere the oil passes, and this can prevent the oil from spread all across the bar. Loosen the nuts holding the clutch cover and disconnect the chain shroud and remove the oil plate. Wipe off lubricant and grime from the bar with a clean rag. Poke the oil feed hole with a 16-gauge wire to unclog it until it slides through the hole smoothly.

2. Replace the oil pump

If cleaning does not help release oil onto the bar, the pump may be damaged and require replacing. Remove the spark plugs and the e-clips attached to the sprocket on the engine shaft. Remove the sprocket and the washer. Block the spark plug’s hole by putting a nylon rope to prevent the piston from moving. Unscrew the clutch assembly on top of the oil pump. Loosen the nuts and bolts clockwise and then pull out the oil pump gently. If it is not physically damaged, clean it with clean gasoline and a rag. If you notice the treads are worn, which prevents the device from pumping, replace it with a new one. Reassemble the chainsaw, refill the fuel tank, crank the engine and check for oil along the bar.

Conclusion

Thus far, you have learned how to diagnose most problems with the Stihl chainsaw and how to fix the issues. Keep in mind that good maintenance and storage will reduce breakdowns and maintain your tool’s performance throughout its lifetime. Whether you are a beginner or a professional woodworker, knowing how to fix your chainsaw will save you time and money seeking help from a service center.

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