Skip to Content

Chainsaw Starts but Dies when I Give it Gas. Tips from a Pro

Chainsaw bogging down after starting or not starting at all is a common problem for a lot of chainsaw users. This can be quite annoying, especially when you have loads of work piled up and a mechanic isn’t available. This article will help you fix your chainsaw by yourself that starts well but dies just after you push the throttle.

Chainsaw starts but dies when I give it gas.

If your chainsaw dies when you give it gas, make sure that the low-speed screw (L) and the idle screw (I) are correctly adjusted. Locate their perfect setting at which the engine doesn’t bog down when the throttle is applied. Besides the screw setting, check and ensure that the spark plug is in working condition and that the carburetor and fuel jets are properly serviced.

The above answer may be brief, but I will explain it in more detail, including how to fix a chainsaw that won’t start.

Why doesn’t my Chainsaw Stay Running?

If your chainsaw starts but does not stay running, the low-speed (L) and idle screw (I) may not be properly set. The fuel lines or ignition system may have been affected if the problems continue despite adjustment.

1. Adjustment Screws:

The carburetor has three adjustment screws marked on it. These are the low-speed screw (L), the idle screw (I), and the high-speed screw (H). These screws are in charge of regulating the fuel flow to the carburetor under varied load circumstances.

The L screw, for example, controls the gasoline entering the carburetor at low/idle RPMs, whereas the H screw regulates the fuel flow at higher RPMs or wide-open throttle (WOT). The (I) screw is a butterfly valve that controls idle RPMs by raising or lowering the flow of the air-fuel mixture.

When a screw (e.g., an L screw) is tightened, the fuel flow to the carburetor is restricted, causing the mixture to be lean. This causes your engine’s RPMs to increase to a set limit before decreasing. Loosening the screw, on the other hand, enriches the mixture with gasoline and lowers the RPMs to a set limit. When the L or idle screws are not properly set, the idle RPMs fall too low, causing the engine to stall and eventually stop.

2. Fuel Flow System:

Your chainsaw’s fuel supply system comprises the gasoline tank, fuel filter, fuel lines, and carburetor. An obstruction in any of these components may disrupt the fuel flow to the engine, leading to the engine bogging down while idling. The use of stale ethanol-blended fuel, which creates sticky white deposits over time, is the most typical source of such clogs.

These deposits often accumulate at the fuel filter or carburetor jets, eventually blocking them and impeding fuel flow. In some circumstances, vapor locks created in the fuel tank due to insufficient venting cause engine issues. All fuel supply components must be independently examined to address these difficulties, as discussed in the following sections.

3. Ignition and Exhaust:

The ignition system includes the spark plugs, ignition coil, and exhaust muffler. The spark plugs’ spark quality degrades over time, making it impossible to ignite the air-fuel mixture in the combustion chamber.

Furthermore, the arrestor screen that catches the spark at the exhaust port is prone to carbon deposits. These deposits affect the engine’s operation and may cause your chainsaw not to start.

How Do You Repair a Chainsaw That Won’t Start?

Proceed with adjusting the carburetor adjustment screws to fix a chainsaw that won’t start. Consider cleaning your carburetor and air/fuel filters if the problem persists. Inspect the spark plug and replace it if necessary.

1. Adjusting the Throttle Screw:

As previously stated, the carburetor comprises three screws (L, H, and I) for managing the engine RPMs at low, high, and idle speeds. If the chainsaw continues to stall, the issue could be with the low-speed and idle screws, which should be adjusted.

– Screw Adjustment at Low Speed:

To carry out the low-speed screw adjustment, follow these steps:

  • Turn on the engine: Start your chainsaw and tighten the chain. Allow a few seconds of idle time. Keep track of whether the engine idles smoothly or if it dies.
  • Tighten the L screw: If the engine dies while idling, tighten the Low Speed (L) screw using a screwdriver to increase the idle RPM. As you tighten it further, the RPMs will begin to fall. Make a note of the location of that point. Loosen the screw further, allowing the RPMs to increase until they start to decline. Make a mental note of the second point’s location as well.
  • Locate the ideal spot: The ideal screw setting should now be somewhere in the middle of these two settings. Turn the screw until the perfect balance is achieved, then stop. At this time, the idle RPMs would be adequate to keep the engine going. Furthermore, the engine responds significantly faster and without delay when the trigger is pulled.

– Idle Setting:

The chain may begin to rotate because the mixture is lean enough to engage the clutch after the low-speed adjustment. If your chain starts to spin, loosen the idler screw until it stops. This is crucial since an idle chain is extremely harmful. If your chain does not rotate, you can skip this step.

Following the L modification, the mixture composition should be adequate to keep your engine running. Sometimes the L adjustment is insufficient, and you must tweak your fuel delivery components, specifically the carburetor and filters.

2. Examine the Fuel System:

The carburetor must be maintained, but first, check that your engine’s filters are thoroughly cleaned.

– Air filter:

Using a screwdriver, remove the air filter cover on the back of your chainsaw. Now, remove the filter and clean the dust buildup using a brush. Cleaning it by immersing it in a soap water solution is preferable. If you observe any evidence of damage or wear on the air filter, I recommended to replace it.

– Fuel filter:

The gasoline filter can be found at the bottom of your fuel tank. Drain the fuel tank and store the gasoline in an appropriate container before bringing it out. Remove the filter from the tank’s bottom and clean the stale gasoline deposits from the filter’s jets with a metal wire. After cleaning, attach it back to the gasoline tank.

– Carburetor:

Get a carburetor repair kit before you begin clearing the blocked jets. A carb cleaner spray is an excellent tool for eliminating sticky deposits from your jets and reviving your carburetor.

  • Step 1: Remove the air filter: Remove the air filter to begin cleaning the carburetor. The air filter is often found at the rear of your chainsaw.
  • Step 2: Remove and clean the bowl: Take the bowl nut and bowl out of the carburetor. Old gasoline and its impurities are typically found in the bowl. Any remains or old fuel should be removed thoroughly.
  • Step 3: Use the carb cleaner: Sprinkle the carb cleaner liquid inside the carburetor and on its components. Always clean the bowl nut, a jet that is likely to get clogged. When spray exits from the other end of a jet, it means that any debris that had become stuck has been cleared.

3. Examine the Spark Plug:

Finally, if all previous procedures fail to provide results, the ignition may be at issue. The ignition system is essentially a spark plug. Even if you are a novice chainsaw operator, these spark plugs should be updated at least once a year.

Because of continuous firing, the spark plug’s electrodes become damaged or acquire carbon deposits, reducing spark quality. If this is the case, the only alternative is to replace the spark plug.

4. Other Causes:

– Vapor Lock:

Vapor lock occurs when the fuel vapor pressure builds up considerably in the fuel tank and isn’t allowed to escape from the tank vents. As a result, the fuel drawn by the carburetor reduces, causing the engine to stop running. To check if there’s a vapor lock, unscrew the tank’s cap and put it back on again. The engine should start by now. As a preventative measure, always keep your tank vents clean.

– Air Leakage:

This may be one of the least anticipated causes of the problem, but it occurs in several cases. The engine and its associated delivery system need to be airtight to maintain adequate temperature and pressure. After considerable usage, specific engine components like the crank seals and the head gaskets wear out and develop leakages.

The effect of air leakage is that it upsets the composition of the air-fuel mixture. As a result, the engine runs at too high or too low RPMs. To identify air leakage, you will need to perform a pressure test on your chainsaw. Once the faulty seal or gasket is identified, it needs to be replaced, and the engine should be up and running.

Why does my Chainsaw Start and then Stop?

If your chainsaw doesn’t start, adjust the carburetor screws till it doesn’t bog down. If the problem persists, inspect the fuel lines and ignition system.

There are three adjustment screws on the carburetor: low-speed (L), high-speed (H), and idling (I). The L screw controls how much fuel enters the carburetor at low speed, whereas the H screw controls how much gasoline flows into the carb at high speed. The idling (I) screw regulates the mass flow rate of the air-fuel combination entering the engine at idle.

It’s worth noting that loosening a screw improves the fuel flow rate and enriches the mixture while tightening the screw has the reverse effect. If the idle screw is too loose, the mixture will be too rich, and the chainsaw will not run at all, even at idling.

Tighten the idle screw with a screwdriver to fix this and see whether the engine RPMs rise. Similarly, adjust the other screws, namely the L and H screws, until the RPMs are at an optimal level that prevents the saw from burning out.

Most engine problems can be solved with the previously mentioned adjusting procedure. If the problems remain, examine the fuel lines and carburetor. Remove the carburetor and check it for damage, cleaning it if necessary. Check the spark plug as well to examine the ignition system. Replace it if the quality has deteriorated.