Trimmer: Engine Lacks Power

The carburetor mixes air and fuel to the proper combustion ratio. Fuel that sits for a long period of time, especially in a 2-stroke engine, has the tendency to gum up the inside of a carburetor, which will restrict the flow of fuel. The procedure for cleaning the carburetor will vary slightly as all models differ. You can disassemble the carburetor and clean all the parts on the inside, or you can purchase a carburetor kit and replace all the internal parts. Remove the covers in order to access the air filter. Remove air filter housing and air filter, then remove the bolts holding down the carburetor and gasket. Next, gently remove the fuel lines by twisting them and pulling, then remove the carburetor linkage. Remove the carburetor. Next, remove the screws on the bottom of the carburetor and pull the bottom off. Remove the gasket and the diaphragm. Remove the primer bulb and the cover. On the bottom of the carburetor, take note of how the lever, spring, and hinge pin fit together inside the carburetor. It is a good idea to take photos to ensure proper reassembly. Remove the screw and pull these parts out of the carburetor. Clean the carburetor with carburetor cleaner, making sure to get inside all the ports. Use a soft-bristled brush if needed. If you notice any corrosion on the inside, you must install a new carburetor, as it is no longer salvageable. Install the needle and lever on the bottom of the carburetor and re-install the screw to secure them in place. Install the gasket, diaphragm, and cover. Make sure to install them in the correct order (referring to your photos). Install the top cover and primer bulb. Re-install the carburetor back onto the engine with a new gasket under the carburetor on the engine, and hook back up the linkages and fuel lines. Re-install the air filter housing and filter. Finally, reinstall any covers you removed to access the carburetor. To adjust the carburetor, start with both screws backed out two turns from the closed position. One should be idle mix and the other should be high speed. Start the engine and let it warm up for five minutes. You may have to keep the throttle open a bit. Slowly turn in the low speed jet until it starts to die, then back it out another 1/4 to 1/2 turn. Next, hold the throttle wide open and slowly turn in the high speed, until it really starts to smooth out and rev high, and start screaming, then back this out until it starts to run rough or slows down, then turn it back in to midway between these two positions. Keep playing with the low speed needle until you get rapid immediate response from the throttle, and good idle with the idle adjustment. Next, play with the high-speed needle, but always back it out from the setting about 1/4 turn or so, from where it runs the smoothest. This setting of backing it out will allow more fuel when under a load, and keep your 2-cycle motor from running too lean. Put a load on it and just tweak the settings a hair at a time. Also, make sure your oil/gas is mixed at the proper ratio. Most will start and run with both screws open two turns initially. Don't close the high speed off any more than necessary, no matter how well it runs.

You will find the air filter at the top of the carburetor. It allows clean flowing air into the engine and prevents small particles from damaging internal engine parts. Over time, the air filter will need to be replaced as it becomes clogged with small particles and debris, starving the engine of air and causing a loss in power. Locate the air filter cover and remove it. It may be attached by screws or just a tab. Once off, remove the filter, and check to see how heavily soiled it is. Replace as needed and re-assemble. This should be regular maintenance to prevent problems.

The fuel filter is located inside the tank. It prevents debris from entering the carburetor and engine, and causing damage. You can remove the fuel filter by inserting a hook inside the fuel tank to pull it out. Check to see if it is partially or fully clogged, as it can limit the flow of fuel to the engine. Fuel filters should be replaced as they are inexpensive and part of a regular maintenance routine.

The gasket seals two joining pieces tightly together, sealing off air and fluids from entering areas where they are not supposed to go as well as keeping them from leaking out. A damaged gasket below a carburetor will pull excess air into the engine, causing the air fuel mixture to be incorrect, resulting in a loss of power. To check the gasket, start by removing the air filter and then loosen carburetor bolts. Pinch off the fuel line to prevent a spill. Remove fuel line and linkage. Check the condition of the gasket; look for tears, rips, or any indications of leaks. Clean both surfaces where the gasket sits. The gasket will need to be replaced at this time regardless of condition as they can only be used once. Reinstall the carburetor, hooking the fuel line back up and reconnecting the linkage. Finally, reinstall the air filter housing and filter.

The spark plug ignites the air fuel mixture in the combustion chamber. An oily buildup on a spark plug will cause the spark plug to misfire or not fire at all, resulting in poor power output. Oily build ups are more common on 2-stroke engines if the oil/fuel mixture is wrong. To check this, remove the spark plug, inspect it, clean it off, gap and re-install. If the spark plug has deposits, corrosion, erosion, melting, or oxidization, then replace it. If the engine spends most of its time revving high, install a cooler running plug to dissipate heat more quickly.

The fuel vent allows air to enter the fuel tank as the fuel level drops during use. If blocked, it will create a vacuum and stop the flow of fuel. The fuel vent is located just off the fuel tank. It will be attached to a fuel line, entering the tank through a grommet along with the fuel delivery and return lines. Once located, simply pull off the clamp holding it onto the lines. You will need a pressure checker to check for a vacuum, which is not a tool most people own. You can also remove the gas cap, if you hear air entering when you remove it then you have a vacuum inside the tank and will need to replace the vent.