Hedge Trimmer: Engine Will Idle But Dies At Full Throttle

A fouled or poorly adjusted carburetor can cause your hedge trimmer’s engine to idle, but die when power is increased. You will find the carburetor underneath the air filter, and once you have located it you can remove the air cleaner cap. At this point you will want to look for any obstructions in the way that could block air flow, and ultimately starve the engine of oxygen. Next, check for any adjustment screws that the carburetor may have. Sometimes the adjustment screws are improperly adjusted and therefore the engine is not getting enough air. Adjusting these settings to lean out the fuel flow will solve the problem. You will also want to locate both idle screws on the carburetor. One should be marked L (low) and one marked H (high). Turn both screws in to shut off fuel then turn them the opposite direction 2 turns and start the engine. It may run a little rough at first, but it should start at these settings. Once the engine is running again, allow it to idle for about a minute. Then, start by turning the L screw clockwise to add more fuel and set the idle. Next, at full throttle, turn the H screw clockwise to set the high idle. When you have the engine running at its best, the problem will be solved (note: this does require some experience and may take a few times to get it right). Some carburetors are fixed, meaning they have no adjustments. If this is the case, you may need to clean out a clogged or gummed up carburetor or replace some of the smaller parts by purchasing a carb kit. See the “Carburetor Kit” section for instructions here.

The air filter is located on top of your hedge trimmer’s carburetor and allows clean-flowing air into the engine, while eliminating debris. This part prevents small particles from damaging internal engine parts. As your trimmer ages, the air filter can become clogged, which will starve your engine of the air it requires. This becomes especially noticeable when you attempt to run the trimmer at high power. To inspect the filter, first remove the cover. The cover is sometimes held on by a tab that you can simply pop open, but you may need a screwdriver to remove some attaching screws. Once off, you should remove the damaged or clogged filter, and simply replace it with a new one, then close the cover. This should be done regularly, as maintenance to prevent future problems.

The fuel filter prevents debris from entering the carburetor and engine, which can damage them. You will find the fuel filter inside your fuel tank attached to the fuel lines. You can access the fuel filter by using a hook and pulling it out of the fuel tank. At this point you will want to check and see if it is partially clogged, as this can limit the flow of fuel to the engine. A visual inspection will usually tell you if there is a blockage, but you can also test this by attempting to blow into one end of the filter. If the filter is clogged, it will need to be replaced, and this should allow your trimmer to run properly at full power.

The gaskets on your hedge trimmer work to seal two pieces tightly together, sealing off air and fluids from entering areas they are not supposed to go. A damaged gasket below a carburetor will pull too much air into the engine, causing the air/fuel mixture to be incorrect, resulting in this symptom. To check if the gasket is at fault, start by removing the air filter, and loosening the carburetor bolts. Next, you will want to check the condition of the gasket. Things to look for are tears and rips, or any indications of leaks. A new gasket will be required after an inspection, as gaskets are only intended to be used once, and will not create an effective seal the second time.

The spark plug’s job is to ignite the air and fuel mixture in the combustion chamber under any condition. A faulty spark plug may not allow your hedge trimmer to run properly at full power. To check the plug for damage/corrosion, first remove the wire and connecting harness from the spark plug. Be careful doing so, as the plugs can be fragile. Next, remove the spark plug and check its condition. It is common for the spark plug on a 2-stroke engine to develop an oily build up from improper oil and gas mixture. Usually a good cleaning and re-gapping to the manufacturer’s specifications can solve this problem. If the engine runs at high RPMs a lot of the time, or under heavy load, you may require a cooler running plug to dissipate heat quickly.

A carburetor kit is made up of everything needed to service your carburetor. A carb kit will not be the direct cause of this symptom, but a new carb kit is a great way to restore your carburetor to new condition. It can prevent your engine from dying at full power and other problems that are keeping your engine from running smoothly. Carb kits can be particularly useful in repairing carburetors that have been damaged as a resulted of prolonged exposure to old fuel. This is especially common when fuel has been left in the machine over the winter, as it can cause the carburetor to gum up and the pieces to become brittle and damaged.

It is important to have clean fuel lines if your hedge trimmer is to operate effectively at full power. Cracked or clogged fuel lines will deprive the carburetor and the engine of fuel, causing it to die when the trimmer reaches full power. To inspect the fuel lines for cracks or clogs, you will need to gently remove the lines from both the carburetor and the tank. Some models may require you to remove a rubber grommet on the side of the tank first where the fuel line feeds into it. To test for a clog, simply blow through the lines, observing any blockages. If you see anything unusual coming out, or hear a blockage, your best course of action would be to replace the line. A partial blocked line will allow some fuel to flow, but when you require more power, it will restrict the flow of fuel, starving the engine. Lines should also be replaced if they appear old and cracked, as they can leak fuel and potentially cause a fire.