Overview
This replacement trimmer head brings your string trimmer back to full functionality when the bump-feed mechanism wears out or the housing cracks. It is an aftermarket unit manufactured to the same dimensions as the original, so it threads right onto your trimmer’s output shaft. No adapters or modifications needed.
Key specifications
- Type: bump-feed trimmer head
- Material: reinforced nylon housing
- Thread: matches OEM output shaft
Compatibility
Compatible with Stihl FS38 FS40 FS40CE FS50CE FS45 FS46 FS50 and related models. Always verify the OEM part number in your owner’s manual against the compatibility list to ensure this replacement will work on your specific machine.
Installation notes
Immobilize the gear-head shaft with the locking hole and pin or a shaft-holding tool. Unthread the worn head and clean any debris from the shaft threads. Screw the new head on hand-tight, then snug it. Load the spool with the correct diameter line, snap the cover closed, and test the bump-feed mechanism before trimming.
Common questions
Q: Will this 4144 640 5900 bearing housing and AutoCut 5-2 head fit my Stihl FS40 C-E, or is it only for the older FS38/FS45 models?
Yes, this replacement is listed to fit the Stihl FS40 C-E along with FS38, FS45, FS46, FS50, FS50 C-E, FS51, FSA60R, FSA86R, FSE60, FSE71, and FSE81 models. As long as your trimmer matches one of those model numbers and uses the 4144 640 5900 bearing housing style, it should be the correct replacement.
Q: Do I need to grease the bearing housing when installing it on my FS50CE, and should the AutoCut 5-2 head be installed at the same time?
It’s a good idea to inspect and lightly grease the gearbox/bearing area if your unit’s service procedure calls for it, especially if the old housing failed from heat or wear. Replacing the AutoCut 5-2 head at the same time makes sense if the old head is wobbling, cracked, or feeding line poorly, since both parts affect smooth cutting performance.
Q: My Stihl FSA86R has vibration at the cutting head—will replacing the bearing housing and AutoCut 5-2 fix that, or should I check something else first?
Worn bearing housings and damaged trimmer heads are common causes of vibration, so replacing both can often solve the problem. Before installation, also check that the drive shaft, mounting surfaces, and guard area are clean and not bent, because a damaged shaft or debris buildup can cause the same symptoms.
