The engine requires a sufficient air and fuel mixture along with spark to ignite this mixture to start.
A Honda string trimmer won’t start due to a plugged air filter, bad spark plug, plugged fuel filter, clogged fuel line, dirty carburetor, faulty recoil starter, plugged spark arrestor, plugged fuel tank vent, or old fuel.
Keep reading for more items that can cause your starting problems including a flooded engine.
Before repairing your string trimmer, remove the spark plug wire and wait for all parts to stop moving. You can find safety precautions for your string trimmer in your Honda operator’s manual.
Reasons a Honda string trimmer has starting problems:
- Clogged air filter
- Bad spark plug
- Plugged fuel filter
- Wrong gas
- Wrong or Insufficient engine oil
- Old gas
- Bad primer bulb
- Blocked fuel line
- Plugged fuel tank
- Dirty carburetor
- Bad recoil starter
- Plugged spark arrestor
- Flooded engine
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
Reasons Your Honda String Trimmer Will Not Start
When you are dealing with a starting problem, replace the fuel filter, air filter, and spark plug if you haven’t recently replaced them. This will rule out these standard maintenance items as being part of the problem.
Replacing these maintenance items should be part of the routine maintenance completed annually on your Honda.
1. Plugged Air Filter in a Honda String Trimmer
An air filter is used on your Honda string trimmer to protect the engine from dirt and other contaminants that can damage it.
Using a string trimmer creates dirty dusty conditions. The air filter can become plugged when it isn’t regularly cleaned or replaced.
The engine is starved of air and will not start. If you find this is your problem, never run your string trimmer without an air filter to get the job done.
This can be a costly mistake. Dirt can enter the air intake and cause engine wear and damage. It may cause so much damage, the string trimmer will have to be replaced.
SOLUTION: Remove the air filter and wipe out any remaining dirt from the air filter housing. Replace a dirty air filter with a new air filter. If the filter is in good condition and just a little dirty, you can clean it using the steps below.
Clean a Honda string trimmer primary FOAM air filter:
- Remove the air filter cover and air filter.
- Clean the foam air filter using warm water and mild detergent.
- Rinse the filter until the water runs clear and allow it to air dry.
- Once dry, lightly saturate the filter with filter oil. Squeeze excess oil from the filter.
- Reinstall the filter.
- Reattach the air filter cover.
2. Bad Spark Plug in a Honda String Trimmer
The spark plug will become dirty over time with a buildup of carbon. This can cause the plug to misfire having intermittent starting problems.
Other items to look for is cracked porcelain or burnt electrode, a loose spark plug wire, and an incorrect spark plug gap. These items can also cause a starting issue with your Honda.
SOLUTION: You can attempt to clean a dirty spark plug with a wire brush and reuse it. I prefer to replace it. It is an inexpensive part and one of the primary items responsible keep your string trimmer running.
Make sure your spark plug is gapped to the manufacturer’s specification and the spark plug wire (boot) is securely attached.
3. Plugged Fuel Filter in a Honda String Trimmer
You will find a small filter in the fuel tank attached to the fuel line. This filter is used to keep dirt and other contaminants in the fuel from getting into the fuel system.
When the Honda fuel filter becomes plugged because it isn’t being changed regularly, the amount of fuel getting to the carburetor may be reduced causing starting issues.
SOLUTION: Locate the fuel filter inside the fuel tank and replace it.
- Wipe around the fuel cap to remove dirt, and then remove it.
- Empty the fuel tank into a clean fuel container.
- Set the trimmer on a flat surface.
- Pull the fuel filter out of the tank using a clean bent wire to hook the fuel line. Needle nose pliers may also work.
- Securely holding the fuel line, securely grab the filter and pull it out of the fuel line.
- Install a new fuel filter at the end of the fuel line.
- Place the filter back inside the fuel tank.
- Fill with fresh gas
- Place the fuel cap onto the fuel tank.
4. Wrong Gas in a Honda String Trimmer
Honda string trimmers with 4-cycle models require straight gas. Use an unleaded gas with a minimum 87-octane rating and maximum 10% ethanol.
Stay away from fuels with high ethanol contents. Using an ethanol-free fuel is best.
SOLUTION: Drain the fuel tank and fill it with the correct gas.
5. Incorrect or Insufficient Engine Oil in a Honda String Trimmer
A Honda string trimmer with a 4-cycle engine will have separate fill ports for the engine oil and fuel.
You will not mix oil and fuel together for this type of engine. It’s important to use the correct engine oil and the right amount of oil.
Never use 2-cycle engine oil in a 4-cycle Honda string trimmer. Honda recommends using 10W-30 engine oil in the string trimmer. This engine oil from Kawasaki works well.
Oil is required to keep the engine components lubricated. When the wrong type or not enough oil is used, friction can build in the engine and overheat causing your string trimmer not to start and possibly damage the engine.
SOLUTION: Drain the engine oil and fill it with the correct oil grade. When running your trimmer in very cold or very hot temperatures, you may have to adjust the viscosity to your ambient temperature.
If you continue to have problems, have a small engine mechanic diagnose the problem and determine whether a cost-effective repair can be made.
Honda 4-Cycle String Trimmer Engine Oil
6. Old Fuel in a Honda String Trimmer
Old fuel left in a Honda string trimmer won’t only cause fuel restrictions, but it can also damage the carburetor and engine. Gasoline can begin to break down as quickly as 30 days after purchase.
The ethanol found in most gasoline attracts moisture from the air. This moisture and ethanol mixture gums up the fuel system and corrodes components.
Because gasoline can begin to go bad as soon as 30 days after purchase, the fuel must be consumed within this time frame. If you are unable to use it in this amount of time, add a fuel additive to stabilize the fuel so it extends its shelf life.
Tips for selecting and storing gas for your Honda string trimmer:
- Always use unleaded gasoline with a minimum 87 octane rating (regular) and maximum ethanol content of 10% (E10).
- Never use E15 or E85 in the engine as this will damage the engine and most likely void manufacturer warranties.
- Use fresh gas and consume it within 30 days.
- Use a fuel additive to reduce moisture, clean the fuel system, and make gas stable a little longer when you are unable to consume fuel quickly.
- When using a fuel stabilizer, add it to fresh fuel. It cannot reverse the effects of old gas.
SOLUTION: Drain any old fuel remaining in your string trimmer. In a clean approved gas can, add fresh gas and a fuel stabilizer. With the cover on the gas can, gently shake the can to mix the gas and stabilizer. Add the mixture to the Honda gas tank.
I like fuel additives like Sea Foam Motor Treatment or STA-BIL to stabilize gas. I use it in each tank of fuel for all of my small engine equipment.
7. Bad Primer Bulb in a Honda String Trimmer
A cracked Honda primer bulb that won’t fill with fuel will not function correctly to get fuel to the carburetor for starting the string trimmer.
SOLUTION: Make sure the fuel line is securely attached to the primer bulb. Replace a cracked fuel bulb with a new primer bulb.
8. Fuel Line Blocked in a Honda String Trimmer
Old fuel sitting in your string trimmer can leave gummy deposits behind and restrict fuel flow. This can clog the fuel line keeping the engine from starting.
SOLUTION: Replace a fuel line on your Honda string trimmer when it is cracked, kinked, or clogged.
9. Plugged Fuel Tank Vent in a Honda String Trimmer
You may find the fuel tank vent on a Honda string trimmer is usually built into the fuel cap. The vent is designed to allow air to enter the fuel tank as fuel is consumed.
When the fuel tank is no longer able to vent, a vacuum will form keeping fuel from flowing out of the tank to the carburetor. When the carburetor doesn’t get fuel, the trimmer won’t start.
A good indication you may have a fuel tank vent problem is when your string trimmer won’t start until you remove or loosen the fuel cap to allow air into the fuel tank.
If it does start, confirm the fuel tank vent is the issue by allowing the trimmer to run with the fuel cap tightened. Wait to see if shuts down and won’t restart until you loosen the fuel cap.
SOLUTION: Replace the fuel tank cap so the air can flow into the fuel tank.
10. Dirty Carburetor on a Honda String Trimmer
The carburetor regulates the amount of fuel that is mixed with air to create combustion in the cylinder. It is common for old fuel sitting in your trimmer to gum up the carburetor clogging fuel passageways.
You will need to clean or replace the carburetor to get your Honda started again when this happens.
SOLUTION: If you are a little mechanical you should be able to handle cleaning your carburetor. Clean the carburetor by taking it apart and using carburetor cleaner to clean it.
If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.
Depending on the model string trimmer you run and the price of a carburetor, it may be best to invest in a new Honda string trimmer rather than put money towards replacing a carburetor on an old trimmer.
Consider the price, age, and model of your current Honda to a new Honda string trimmer.
11. Bad Recoil Starter on a Honda String Trimmer
Your Honda string trimmer uses a recoil to start the engine. A bad pulley; loose or missing spring; or broken clips can keep your recoil from working.
SOLUTION: You can attempt to replace the spring and restring the recoil.
If it does not work because other components in your recoil are damaged, such as the clips or the pulley, you are better off just replacing the recoil assembly.
12. Plugged Spark Arrestor in a Honda String Trimmer
You will find a spark arrestor in a Honda string trimmer with a catalytic converter. The spark arrestor is a small screen that is used to prevent hot exhaust material from shooting out of the Honda causing injury or a potential fire.
The screen can become plugged with soot and prevent hot exhaust air from leaving the trimmer. This can cause a Honda trimmer to not start.
SOLUTION: Disconnect the spark plug boot. Make sure your engine is not hot. Remove the engine cover and engine exhaust cover.
Remove the spark arrestor and clean it with a wire brush to remove the soot. If you are unable to sufficiently clean it or it has a hole in it or is damaged, you need to replace it with a new spark arrestor screen.
13. Flooded Honda String Trimmer
The engine may become flooded when attempting to start it and now it won’t start. This isn’t too serious of a problem and can easily be fixed.
The Honda engine can become flooded when the choke is in the closed position and the starter rope was pulled many times allowing too much gas into the carburetor.
It can also happen with the switch off and the starter rope being pulled multiple times or when the primer bulb is pushed too many times.
SOLUTION: Use the following procedure to “unflood” your string trimmer so the engine gets the correct fuel-to-air ratio required to start and run.
How to Fix a Flooded Engine on a Honda String Trimmer
- Move the stop switch to the run position.
- Place the choke lever in the open/run
- Press the throttle trigger while pulling the starter rope over and over. This can take anywhere between 5 and 15 pulls before it starts. Your string trimmer engine will sputter first. Continue to pull a few more times and it should start.