How to Fix Continuous Spinning of the Weed Eater String

A weed eater does not come with any blade or sharp cutting tool. Instead, it uses a flexible string line that spins around at a high speed. Almost every weed eater comes with a throttle for adjusting the strength of the spin higher or lower.

When you push or pull on the throttle, the string spin and the speed will increase by an equivalent amount. Once you release the throttle, the string stops spinning entirely. The clutch system of a weed eater is similar to the clutch system of a chainsaw for those who are familiar with how chainsaws operate.

However, at times the system will become faulty and the string will continue to spin even when you release the throttle. It is risky to make use of such a weed eater as it can cause injury to the user or even damage something perhaps wrecking the lawn. It is therefore imperative that you find out the cause and correct it before you start using it again.

This guide refers only to gasoline weed eaters as electric weed eaters do not use the same system of operation and will not run across the same kinds of issues.

trimmer head keeps spinning

Possible Causes

When the string of your weed eater continues to spin after you have released the throttle, there are two possible causes of such a problem. It might be that the engine is idling too quickly or the clutch is not functioning well and requires servicing. Any of the causes can be corrected easily without requiring any expert attention.

  • Engine Idling Too Quickly

The first thing you should check if you are experiencing a problem with idling speed is the engine of your weed eater. Do this to find out whether or not it is idling as quickly as you think. If it is idling too quickly, the clutch shoes may not be able to retract and this will cause the string trimmer to continue spinning after you have released the throttle.

You can solve this problem by tweaking the speed of the idle. This can easily be done. Find the adjustment screw on the carburetor. You can identify it with the mark “I”. Turn the screw counterclockwise while the engine is still running. This will cause the engine to slow down so that the head will be able to stop the string from spinning. If this does not work out or if the head does not stop before the engine dies, you should consider servicing the clutch.

A benefit you can get from adjusting the engine is that it will stand to enhance performance and reduce fuel consumption.

  • Understanding the Working of the Clutch System

Weed eaters normally come with a centrifugal clutch through which its drive shaft connects to the flywheel of the engine. The centrifugal clutch is located at the engine housing’s front. The clutch has two components: a shoe assembly (connects to the engine) and a housing or drum (connects to the shaft of the trimmer).

The shoes are held together and compressed by the string until they are separated by the force of the engine as it spins fast enough. As they separate, they contact with the drum to turn it on. When the engine slows down, the string trimmer will pull the shoes back again and the drum is turned off.

weed eater spins at idle

Possible Malfunctions

There are two different ways through which the clutch can fail.

  • First, the friction coating on the shoes can become worn out as a result of usage. This can cause the shoes to slip against the drum. When this happens, the string head can either stop spinning or spin intermittently. The shoes can also be contaminated by oil if it gets into the clutch.
  • The second cause of the clutch malfunctioning is when the shoes do not retract and maintain steady contact with the drum. This results when there is a broken string trimmer. Corrosion can also cause it. A broken string trimmer can be replaced. Alternatively, the entire clutch system can be replaced if necessary.

Gaining Access to the Clutch

Empty the fuel tank of your weed eater. Remove the drive shaft, which should be secured to the engine housing with a screw. Some models may require that you remove the throttle cable as well as the ignition wires. Then, unscrew the single screw that keeps the clutch drum secure. You should ensure that the pistol does not make any movement.

You can prevent the pistol from moving by closing the spark plug hole with a nylon rope. The drum will come out when you remove the screw. The removal of the drum will make it possible for you to unscrew the shoe assembly. You either replace it if it has too much damage or repair it. If you are replacing it, you should consider replacing the drum as well.

If none of these troubleshooting solutions solve the problem of the string spinning when the throttle is off, you may need to take the weed eater to a professional and have them look at it.