International België (nl) Belgique (fr) Danmark Deutschland Eesti Ελλάδα España McCulloch France Français Italia Latvija Lietuva Magyarország Nederland New Zealand Norge Suomi Sverige United Kingdom United Kingdom Österreich

Chainsaw Troubleshooting - Why Has My Chainsaw Stopped Working

It is important that your chainsaw is in good working condition in order to get the best out of it when you have a job to do. If your machine does stop working you will need to check what repairs you can do without voiding the warranty. If you are unsure you can query it with a registered repair agent. Here at McCulloch we have dedicated service agents across the country that you can find here.

When diagnosing different issues with machines, you will need to understand the different components that go into making a chainsaw work. As an example, the diagram below shows the main components in a McCulloch CS 42S Chainsaw.

1.Combination tool 2.Chain 3.Front hand guard
4.Muffler 5.Front handle 6.Starter rope
7.Idle speed screw 8.On/Stop switch 9.Choke/fast idle lever
10.Primer (air purge) bulb 11.Fuel mix fill cap 12.Starter housing
13.Bar and chain oil fill cap 14.Bumper spike 15.Cylinder cover
16.Throttle lock-out 17.Rear handle 18.Throttle trigger
19.Clutch cover 20.Chain catcher 21.Guide bar
22.Chain brake 23.Cutters 24.Depth gauge
25.Drive links 26.Chain direction of travel 27.Guide bar retaining nuts

With roughly 30 different components to most petrol chainsaws, make sure that you are confident with the repairs that you need to carry out. The manufacturers manual provides additional information as to what is required; however if in doubt consult a specialist so you don't void the warranty.

To make things easier here are the most common issues that you can experience with your chainsaw.

The Chainsaw Won't Start

A non-starting chainsaw can be caused by several issues. When diagnosing the issue, it’s important to remember to wear safety equipment and hold the chainsaw correctly as it can suddenly re-start at any moment.

Spark plug

As with most chainsaw maintenance you will first need to remove the spark plug where applicable. Not all chainsaws will have spark plugs however for petrol machines this can be one of the main causes of a non-starting machine. Not only is this a good safety tip to ensure the chainsaw doesn’t spontaneously start, but it could also be a factor as to why the product will not power up. By removing the spark plug you can see if it is faulty, which would cause the machine to not run properly.

You should ideally look to replace your spark plug every couple of years to keep your machine in good working order. If the porcelain insulator on the spark plug is cracked or there is a heavy carbon buildup you should consider replacing the spark plug to get your machine working again. Likewise, if one of the electrodes has been burned away from extended use it’s best to replace the plug.

Ignition Coil

If the spark plug isn’t the problem, then it is possible that it could be the ignition coil. This is the component that sends the current to the spark plug while the machine is in use. If it still isn’t working, it could be a problem with the coil. You can use an ignition coil tester to determine if it is broken or not however it may be worth consulting a professional at this point as if it is defective you will need to replace it.


Issues with the carburetor can also cause problems with the chainsaw. If petrol has been left in the machine for a considerable length of time it can clog up the carburetor, causing starting issues. This is because petrol goes stale after a few weeks as some of the ingredients evaporate, leaving the resultant mixture dense and sticky which can ruin the carburetor. If this is the case and your carburetor is clogged you can try cleaning it with a special carburetor cleaner. Otherwise you may need to replace or rebuild the whole carburetor.

Air Filters

In order for the internal combustion engines to work air needs to be sucked into the machine so the fuel can ignite. If the air filter is clogged as a result of a carbon build up this can restrict the airflow and in turn hinder the whole chainsaw. This should be checked after each season and cleaned or replaced when necessary.

Blown Fuses

This is only relevant to electric machines with extended cables that plug into the mains. Fuses are designed to protect the wiring against electrical faults, which cause too much current. If you are using an electric machine and are struggling to get it going this should be the first port of call.

The Chainsaw Starts And Then Stalls

It can be very frustrating if your chainsaw cuts our midway through your task leaving your job half complete. Luckily diagnosing isn’t always complicated.

Spark Arrester

The spark arrester is a screen that is designed to prevent sparks from emitting from the engine. After a while it can become congested with soot, which can cause it to fail. If it does fail it can make the machine stall or run rough. In order to combat this you will need to remove it and clean it with a wire brush. This part can also be replaced if necessary.

Similar to the reasons above, the carburetor can be a cause for the machine to stall mid-use. If the carburetor gets clogged as a result of stale fuel it can cause many issues with the chainsaw. It is always recommended to use fresh fuel anyway as the fresher the fuel, the more efficient the machine will run.


As with the reasons above the carburetor can be a common cause. You may have to disassemble it and clean each part with a carburetor cleaner before rebuilding it. This can be a painstaking job so it may be more worthwhile to refer to a professional.

Air and Fuel Filters

If the issue is still unsolved, you should look to check the filters. The air and fuel filters can get clogged or dirty which can result in the engine stalling. If these filters are clogged you should try to clean or replace them.

The Chainsaw Chain Isnt Turning

If you have this type of problem you will need to be careful how you proceed when you come to diagnosing the issues so you don’t damage the engine. If your chainsaw chain isn’t turning there are a number of different culprits that can be keeping you from getting the job done.

Chainsaw Is Damaged

The first thing you should check is that the bar doesn't have any signs of damage. If you see signs of damage you should either contact the manufacturer or a service agent before completing any further work. The chainsaw is a dangerous machine if used improperly and a damaged bar will only raise the risk.

If the bar itself doesn't have any signs of damage you should also check the drive assembly. Any problems here will mean the power from the engine cannot move the chain. If you do find any issues here you should check for any relevant information in your manufacturers manual. If this still doesn't help you should get the machine looked at by a professional.

Chain Brake

The chain brake is designed to halt the chain when you aren’t working so you can move the machine safely between jobs without turning off the engine. If this chain brake is disengaged and the chain still isn’t moving it is possible that there is a fault with the chain brake mechanism keeping it locked. If the clutch cover is removed while the chain brake is engaged this can lock the chain, and can be tricky to rectify, as it can be difficult to replace the clutch cover. You can fix this by resetting the chain brake.


It is also possible that the clutch can be the culprit. The clutch is attached to the crankshaft, which turns over when the engine fires. The clutch is then engaged to the crankshaft once the speed of rotation is accomplished – similar to the clutch on your car. This means that the engine can run without the clutch engaged with the crankshaft. If the clutch or the springs are broken this could mean that the clutch may not engage at all. Clutches are easy to replace once the side cover has been removed.


If none of the above solves the problem the most likely issue is with the chain itself. If the chain has been tensioned too tight this can mean that the blade may not spin when the engine is engaged. This can cause damage to the clutch as well as other components. You should be aware that the tension would alter with change in temperature when the chainsaw is in use - it will heat up and will be much looser on the bar. When working, you ideally should look to stop after roughly half an hour to check the tension if necessary.

Chainsaw Not Cutting

Often issues of this nature aren’t as much as a result of a mechanical fault but are rather a build up over a few years of hard graft without replacement or servicing. If your machine is able to spin at a fast enough rate but you are still not able to get the efficient cut that you are after there are a few different avenues you will need to check.

Cutting Chain

If the chainsaw isn’t cutting to its usual degree of efficiency it can simply be a case that the chain has become too dull as a result of a long life in use. After a while the sharpness of the teeth on the blade can wear away which means the blade cannot be as efficient. It is a simple fix, however as you will just need to replace the chain you should refer to the manufacturer’s manual for the exact specifications of the chain you will need.

Chain Tension

If the chain is sharp enough then perhaps it isn’t tight enough. If the adjustment screw isn’t tight enough then the chain will fail to make a clean contact with the material. If the chain is too tight then the chain may not be able to rotate as fast as it can, which can also lead to a poor cut. You can adjust this with the chain tensioning screw.

Chain Bar

The chainsaw could also be struggling to cut properly due to a bent or worn out chain bar. Ideally the chain would slide easily around the bar so if this doesn’t happen then you may need to replace it. You will also need to make sure the bar is well lubricated so make sure you fill the reservoir with chain oil every time you refuel the machine.


The clutch pads engage the clutch drum to engage the chain. If they become worn out, they won’t be able to exert enough pressure, which will mean the machine will not be able to function at its usual efficiency. If this is the case you will need to either repair or replace the clutch assembly.