How to start a gas string trimmer

Fuelling a Gas Trimmer

Gas trimmers have engines that utilize oil or gasoline to operate. Needless to say, it won’t work with an empty fuel tank, so, of course, this means that you will need to top up the fuel system with gasoline before you can use it.

However, fuel system preparation is not as easy as just pouring in gasoline in the tank. There are different conditions depending on the type of engine your gas trimmer has.

These engines are categorized into two:

  1. Two-stroke or Two-cycle Engines
  2. Four-stroke or Four-cycle Engines

Now, these two categories have their distinct characteristics, but the most important distinction between them is their fuel requirement. Let us take a closer look at each engine’s fuel requirement below.

Two-Stroke or Two-Cycle Engines

Two-stroke engines require a mixture of gasoline and lubricating oil to properly function.

Mixing Fuel for Two-Stroke Engines

For two-stroke engines, the general oil to gas ratio is 1:50. This is equivalent to 20 ml of oil per liter of gas. To guide you better, we have provided a conversion table for an equipment with a 1:50 ratio.

Fuel Mixture Oil Gasoline
1 liter 20 ml 1 liter
5 liters 100 ml 5 liters


Sometimes, manufacturers recommend different measurements for their equipment. Other oil to gas ratio that is commonly used in mixing fuel for two-stroke engines are 1:25, 1:30, and 1:40. This is why, it’s better to consult the manufacturer’s manual before doing any actual mixing.

Friendly Tip: Bottles of pre-mixed fuel for 2-stroke engines are available in the market. You can opt to purchase one if you are having a hard time mixing gas and oil.

Four-Stroke or Four-Cycle Engines

Four-stroke engines, on the other hand, already have a lubricating system installed, so you won’t need to mix oil in the gas to fuel it up.  They are mainly powered by gasoline alone, so filling them up require less effort and time.

Note: Never attempt to use 4-stroke motor oil in a 2-stroke engine. It contains additives that can possibly contaminate the cylinder and tar up the piston of your engine.

Starting a Gas String Trimmer

Step 1: Place the gas string trimmer on the ground.

Make sure the gas tank is sealed before attempting to start your trimmer. Place it gently on the ground. Remove any obstructions or objects that might get caught in the spinning line of the cutting head.


Step 2: Flip the kill switch on.

The kill switch serves as the on/off switch. Its location usually depends on the the model and type of your “best gas string trimmer 2019“. But generally, it is located somewhere along the shaft.


Step 3: Switch the choke to the “closed” position.

This is done when cold starting you string trimmer. A cold start refers to starting the engine when its temperature in cooler than the temperature it usually runs at. By repositioning the choke, airflow will be restricted, making it easier to start the engine.


Step 4: Press the purge valve 5 to 6 times.

The purge valve is also referred to as the primer bulb. It is a bulbous piece of rubber that is similar in shape and size to an outer glass shell of a light bulb. By pressing it, fresh gas is able to flow to the carburetor.


Step 5: Firmly grip on the trimmer’s throttle lock and pull the cord.

Most gas string trimmers have a pull start-up mechanism. In this case, make sure that you are holding on the throttle lock. It is a small lever that is strategically placed on top of the trimmer’s shaft. Pull the cord as many times as you need until the engine starts to run.

Note: Make sure that you do not squeeze the trigger while you are pulling the cord.


Step 6: Stop pulling the cord once it starts to run.

If this is executed properly, you will hear the engine stop running. The goal of this step is to make the engine burp as preparation for the actual start-up. Do not pull the cord immediately after the engine stops running.


Step 7: Switch the choke to the run position.

Generally, the choke aids in making it easier to start the engine. However, since you were already able to make the engine run, you will no longer need the assistance of the choke.

Switch the choke to the run position to encourage proper air flow in the engine to keep it efficient. Although the choke allows a cold engine to be started, it will actually result to higher fuel consumption if kept on while operating the equipment.


Step 8: Place your hand on the throttle lock and pull the cord again.

Squeeze the throttle control, then pull the cord until you hear the engine starts to run. This time, the engine should continue running.

Note: Make sure that you do not squeeze the trigger while you are pulling the cord.


Step 9: You’re ready to go!

Now that you’ve successfully started the engine, the string trimmer is ready to go.

Note: This step-by-step guide is intended for starting a cold engine. If you have recently just used the string trimmer, the engine should still be considerably warm. Hence, you won’t need to use the choke and the primer. In starting a warm engine, skip steps 3 to 7. You only need to flip the kill switch and pull the cord to start it up.


Solving Common Start-up Issues

Are you having trouble starting your string trimmer?

Here are some troubleshoot guide in starting your trimmer effortlessly.


# 1 Did you prime the engine properly?

Oftentimes, a gas string trimmer needs more priming especially if it’s mostly left sitting around. Press and release the primer bulb, also known as purge valve,  10 times, then try starting it again.


# 2 Does the fuel in your tank seem stale or improperly mixed?

Sometimes, improper mixing of fuel or stale fuel can hinder the engine to start running. In this case, it is advisable that you empty the fuel tank and refill it with fresh fuel.


# 3 Is the engine flooded?

If the engine seems to be flooded, move the choke lever to position 3. Once ready, squeeze the throttle control and pull the cord to start the engine again.


# 4 Is the air filter of your string trimmer clean?

Sometimes, the air filter can also affect the start-up mechanism of your string trimmer. Check if there are problems with your air filter. You might need to clean it or replace it, depending on its condition.


# 5 Is the spark plug fouled?

Inspect the condition of your spark plug. If you see that it has blackened, corroded, or damaged, you might have to replace it.


# 6 Is the trimmer in the correct choke position?

T start the starting sequence on a cold engine, the choke lever should be in position 1 or the “closed” position.

Enjoy reading how to store a gas string trimmer or How does an automatic feed string trimmer work?


Leave a Comment