Stihl Trimmer Head is Stuck (5 Reasons+ Solutions)

Who doesn’t love the smell of freshly cut grass and a beautiful lawn in the summer? Well, to groom the grass, Stihl Trimmers is an environmentally-friendly choice. 

It may come with many advantages. But one of the disadvantages is that the head of the trimmer doesn’t spin. 

So, what to do if stihl trimmer head stuck? 

If the trimmer’s engine is running but the head is stuck, you need to troubleshoot it. Check your trimmer’s clutch, gearbox, shaft, throttle cable, and housing. Identify your problem and solve it accordingly. 

To identify your trimmer’s problem, we curated a general guide for you. So what are you waiting for? Let’s start!

How To Troubleshoot the Stuck Trimmer Head?

Here we’ll describe how the trimmer’s different parts can be responsible for the head not spinning. And what you can do to solve this problem. So, let’s get started- 

1. Damaged Clutch

The clutch may be damaged if the trimmer head does not spin. But the trimmer engine operates when the throttle is pressed. 

The clutch causes the driveshaft to begin moving whenever a specific rotational speed is reached. This allows the engine to run without the drive shaft rotating constantly. 

The clutch may not engage at all if it’s damaged or the springs are improperly tensioned. 

Solution

To obtain access to the clutch, disassemble the engine case and inspect it for damage. Detach the spark plug and insert a piece of scrap starting rope into the combustion chamber. This is to keep the piston from moving while the clutch is uninstalled to secure the trimmer. 

If your clutch is broken, it has to be replaced. Consult your user handbook for the correct part number.

Here are some of our suggested clutches, take a look and see if they match yours-

2. Damaged Drive Shaft

The shaft links the engine’s crankshaft to the trimmer head. The crankshaft is connected to the driving shaft and a gearbox. It enables the trimmer’s head to spin. 

The trimmer head will not spin if the drive shaft is damaged or disconnected. 

Solution

Remove the engine assembly from the driveshaft and check to verify if it’s an inappropriate location. If the shaft has fallen out of place, reinstall it. 

The shaft must be replaced if it is badly damaged. Disconnect the engine housing from the drive shaft housing. 

On some models, the ignition wires and throttle cable may need to be separated. Detach the drive shaft with needle-nose pliers once the shaft housing has been removed from the unit. 

You can get needle-nose pliers form our suggestions below-

Re-install the shaft into the housing after lubricating it from top to bottom with grease. Rotate the shaft in the trimmer head coupler until you feel it lock into place. 

This is a time-consuming process of trial and error. 

The end of the shaft should be flush with the shaft housing once it is locked into position. Return the engine and driveshaft assembly to their original positions. Reconnect the ignition and throttle wires.

3. Gearbox Failure

The failure of the teeth on the gearing is the most prevalent problem with gearboxes. This might happen gradually over time as a result of natural wear. Also if the trimmer is overworked or misused fast. 

Lack of lubrication might be a problem as well. The absence of lubrication will not cause the gearbox to seize. But, damage to the gears caused by the lack of lube would. 

Solution

It needs to be replaced. Remove any coverings on the head that prevent debris from flying. Especially if they are in the way before removing the gearbox. 

Insert a screwdriver into the hole on the gearbox immediately above the trimmer head. Rotate the trimmer head until the screwdriver is securely fastened. And remove it by spinning it counterclockwise. The threading on the trimmer heads is reversed. 

Now remove the gearbox by unbolting it. Tighten the bolts after installing the new gearbox and rotating the spindle until it lines up with the inner shaft. Replace the flange and trimmer head, taking in mind that the threads are in the wrong order. 

4. Damaged Throttle Cable 

The throttle cable links the carburetor to the throttle trigger. When the cable is pulled, the carburetor’s throttle opens, allowing the engine to accelerate. 

The engine will not accelerate if the throttle wire is damaged, and the trimmer head won’t spin. 

Solution

Replace the throttle cable if it is broken. There is no other fix to this.

5. Broken Shaft Housing

The driveshaft can be stopped from spinning if the shaft housing is broken. And also if it exerts pressure on the drive shaft inside the housing. 

Solution

The quickest and most basic solution is to replace the drive shaft unit. 

Remove the screws that connect the driveshaft to the engine and detach it from the engine. Pull separate the throttle and ignition cables if necessary. 

Reattach the replacement drive shaft housing assembly to both ends, tightening the nuts and screws as needed. Then reconnect the ignition wires and throttle cable.

For your convenience, we’ve suggested some good quality drive shafts for you-

So, these are the 5 parts of the trimmer you need to look into. Test one by one of the parts of the trimmer when the head doesn’t spin. And make sure to keep your trimmer under proper maintenance.

Frequently Asked Questions

Question: How do you remove a stuck bump knob?

Answer: Grab some pliers, squeeze the axle tightly, twist the cap and it’ll do the work. 

Question: How do you remove the head of Stihl FS-55R? 

Answer: Rotate the head clockwise with one hand until the stop pin prevents it from rotating. The shaft has now been stopped, causing the head to lock into place and not revolve. To remove the metal nut on the top of the head, use a pair of adjustable pliers to spin it clockwise.

Question: Why does my trimmer line keep coming out? 

Answer: The spring may come out of the head due to excessive usage or a faulty attachment. If this is the case, your trimmer head is no longer spring-loaded. The trimmer line will continue to come out without the spring. As a result, double-check that the trimmer head has its spring. 

Conclusion

So, which part of your Stihl trimmer is the reason your stihl trimmer head stuck? I hope our suggestions helped you to figure it out. 

Let us know if you could solve your problem and how you did it. Take care!