Many owners of chainsaws know the weaknesses of their tools, but there may be situations when you can’t find a problem right away.
This chainsaw repair manual will be also useful to those who recently purchased a chainsaw.
So, your chainsaw has stalled…
There may be many reasons for that, as even though a chainsaw is not a Formula 1 car, it is still a technical device. A key condition for successful repair is the correct diagnosis.
Do not immediately start disassembling a chainsaw, check the simplest possible causes of the failure first. We will give you approximate steps for the diagnosis of your chainsaw.
Chainsaw Repair: Diagnosing Problems
If your chainsaw died for no apparent reason and you have no idea why you should check it for all possible problems. Of course, there are typical problems, that we will talk about below, but let’s go step by step!
1. Check the fuel mixture
Firstly, the fuel mixture must be made according to the manufacturer’s recommendations and with high-quality components. Secondly, use a tank completely or drain the fuel mix before prolonged downtime or conservation between seasons.
2. Clean or change an air filter
A dirty air filter does not allow supplying air in the amount required for the normal chainsaw functioning. That is if a carburetor mixing the air and the fuel mixture was adjusted with a certain amount of supplied air, if the air filter gets dirty, the number of air decreases, while settings are the same and the result is the rich fuel-air mixture.
3. Check a spark plug
There may be several sub-paragraphs here as well. First, unscrew a chainsaw spark plug and check if it was flooded during attempts to start. This is a usual thing when a chainsaw is started by inexperienced users who do not follow the steps for starting a cold saw. In this case, dry a spark plug or screw in a new one and try again following the instructions. The spark plug tip may be broken down. Check this by unscrewing a spark plug, insert it into the tip, put it on the unit, and pull the starter cord a couple of times. If there is a spark, both a spark plug and other electronics work fine.
Another step in checking a spark plug is checking a gap on a spark plug for soot. See your gap size is in the manufacturer’s recommendations. It is usually from 0.5 to 0.65 millimeters. Use fine-grained sandpaper or a metal brush to clean a spark plug from soot.
4. Check a fuel filter
Just like in the case of an air filter, a fuel filter may affect the composition of the fuel-air mixture. The only difference is that if an air filter is dirty, the fuel-air mixture is rich, and if a fuel filter is dirty, the mixture is lean. A saw engine will not work with an insufficient amount of fuel. In addition, when a fuel filter is clogged, the fuel is unevenly supplied to the carburetor and then to the combustion chamber. This is especially evident when a chainsaw dies when giving gas.
5. Check a breather
A breather is a check valve, located in the petrol tank of the chainsaw and preventing the state of vacuum in the tank. If it is clogged, the air is not supplied instead of the used fuel mixture and the fuel pump can not cope with the fuel supply. It often happens that when the fuel was pumped into the carburetor with a primer (a pump for preliminary fuel pumping) – a chainsaw starts. But when the fuel in the carburetor runs out and is not supplied as the breather is clogged – a chainsaw dies.
6. Check a carburetor
In 50% of cases, if not more, a chainsaw dies because of a misconfigured or failed carburetor.
What are possible carburetor problems?
- Jets, nozzles, filters, channels are clogged. A carburetor must be disassembled and cleaned. Please, note that a carburetor consists of small and tiny parts! Therefore, prepare a place in advance before disassembling it!
- The accelerator pump needle gets stuck. Often, as a result of wear or foreign objects, an accelerator pump needle may “get stuck”. In this case, a chainsaw may simply not start, work unstable or stall for no apparent reason at any time.
- The check valve needle is loose against the seat. In this case, a spark plug will be flooded, a saw will run unstable or stall under load. Fitting a needle to the valve seat is very difficult! It is often easier to replace the carburetor …
- Wear or damage a rubber cuff in the accelerator pump. If a cuff has tiny cracks or was damaged, for example at disassembling, then an additional inflow of air (“suction”) will start. This, in its turn, will lead first to an increase in speed, and then a chainsaw will simply die. All you have to do is replace the cuff.
- Sometimes it happens that there is an air inflow from under the carburetor gasket. Determining where exactly the place of inflow is often very difficult and in this case, you might need to change all the seals and gaskets.
7. Checking hoses, seals, gaskets
One of the most common problems why a chainsaw dies or does not start is air inflow. It can be in many different places. Check them one by one:
- Fuel hoses. Often over time or when using poor-quality materials, there may be micro and even bigger cracks in fuel hoses. Cracks can be usually detected if checking visually. It is also worth checking the hose attachment points. If a hose does not fit tightly, there may be a suction there.
- Oil seals. Even the best quality seals can lose their tightness over time and operation. In this case, the quality of the fuel-air mix is damaged and a saw is either unstable or starts and dies. How can you check the oil seals? There are just two of them and both are mounted on the crankshaft. I know two methods of checking their tightness at home:
1. Check them by supplying air under pressure.
You can do this using a compressor, better a stationary one, but a car compressor can be used as well.
You must jam all the holes, exactly the output from the muffler side and the inlet from the side of the carburetor. Then, unscrew a spark plug and supply air under pressure. If there is no pressure or you just hear a hiss, this means that you must replace the oil seals.
2. Checking with a special device.
- Gaskets may also cause air suction. Most often they get damaged at the unqualified chainsaw repair. If you recently dismantled your saw, it is very likely that the suction of air is a result of gasket damage or its incorrect installation.
8. Checking a muffler
After a long operation, especially if the fuel mix was prepared with excess oil, there may be deposits in the muffler preventing easy removal of waste gases. In this case, you must clean a muffler.
9. Failure of the cylinder-piston group (CPG)
This is probably the most unpleasant failure of all possible chainsaws Replacing the CPG often costs more than the cost of half the entire chainsaw! This is especially true for professional models. In our case, when we consider the reasons why a chainsaw dies, problems may be caused by scuffing on the walls of the cylinder and the piston. You can check this by removing a muffler and visually inspecting the surface of the cylinder and piston. In most cases, burrs are from the side of the muffler, but sometimes they can be on the opposite side. Keep this in mind!
Chainsaw Repair: Recommendations
Be sure to use all fuel before preserving the chainsaw for winter or just for a long time. These are probably the main reasons why a chainsaw may die. If these recommendations didn’t help, describe your symptoms in the comments. We are here to help!
FAQ of Chainsaw Problems And How To Solve Them
1) Chainsaw dies when giving gas
One of the most common questions!
In this case, you must:
• Check a fuel filter.
• Inspect fuel hoses for leaks.
• Check a muffler.
• Try increasing the number of XX turns a little.
• Check rubber seals on the crankshaft, the spacer between a carburetor and cylinder.
2) Chainsaw dies when hot
If a chainsaw starts up fine before it gets hot, but it dies and does not start up when it is hot until it cools down, the problem is:
• Check it for any suction (hoses, seals, gaskets)
• Check a muffler for soot.
• Check a cylinder head (cylinder-piston group) for burrs.
• Check carburetor settings
• The ignition coil may be damaged. When the saw is hot, resistance increases and the spark either becomes lost or so weak that its power is not sufficient to ignite the fuel-air mix.
3) Chainsaw dies after releasing the trigger
In this case, you must either adjust a carburetor or there is a powerful inflow of air somewhere.
4) Chainsaw throws fuel into the air filter
Carburetor repair or replacement is required.
5) Chainsaw dies under load
If your saw starts up fine, works both at idle and when adding “gas”, but it dies under load, do the following:
• Check a fuel filter
• Adjust a carburetor
• Check hoses, gaskets, and seals for suction
• Check clutching
6) Chainsaw dies after a while
There may be two reasons:
• Air inflow
• A breather in the gas tank is clogged