Cause 1

Clutch

The clutch engages the clutch pads to spin the trimmer head. If the clutch assembly is defective, the clutch will not disengage the clutch pads, and the trimmer head will continue to spin, even at low speeds. If the clutch is defective, replace it. (Note: some string trimmers do not have a clutch. If your string trimmer does not have a clutch, the trimmer head will spin whenever the engine is running.)

Cause 1

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to stall. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 2

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to stall. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 3

Spark Arrestor

The spark arrestor is a small screen that prevents the engine from emitting sparks. Over time, the spark arrestor can become clogged with soot. If the spark arrestor is clogged, the engine may stall. To unclog the spark arrestor, remove it and clean it with a wire brush. You may also replace the spark arrestor.

Cause 1

Trimmer Housing

The trimmer housing might be cracked, chipped or broken. Inspect the trimmer housing for damage. If the trimmer housing is damaged, replace the trimmer head.

Cause 2

Trimmer Line

The trimmer line might be the wrong size. If the trimmer line is too thick or too thin for the trimmer head, the trimmer line won’t feed. Make sure you are using the correct trimmer line for your string trimmer.

Cause 3

Trimmer Head

Try removing the trimmer head and cleaning it thoroughly. If the trimmer head is worn out, replace it.

Cause 1

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 2

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 3

Spark Plug

Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.

Cause 1

Trimmer Head

If the threads on the drive shaft are stripped, the trimmer head will not stay on the shaft. If this happens, replace both the trimmer head and the drive shaft.

Cause 2

Drive Shaft

The drive shaft is a long, flexible shaft which connects the clutch to the trimmer head. The drive shaft engages the trimmer head. If the drive shaft is broken, the string trimmer head won’t spin. The drive shaft is not repairable—if the drive shaft is broken, you must replace it.

Cause 3

Clutch

The clutch engages one or more drive shafts which attach to the trimmer head. If the clutch assembly is worn out, it won’t be able to engage the drive shafts to rotate the trimmer head. You may be able to clean and repair the clutch assembly. However, since replacing the clutch is relatively easy and inexpensive, it may be easier to replace the clutch assembly.

Cause 1

Fuel Filter

The fuel filter might be clogged. A clogged fuel filter is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the fuel filter and cause the engine to run roughly. If old fuel was left in the string trimmer, drain the old fuel from the fuel tank and replace the fuel filter.

Cause 2

Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to run roughly. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Cause 3

Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to run roughly. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.