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 FS40C-E FS50C-E FSE81 FS45C-E FS36 FS40 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 6-2 head fit my Stihl FS45C-E, or is it only for the older FS45 models?
Yes, this replacement is listed to fit both the FS45 and FS45C-E, along with models like the FS38, FS40C-E, FS50C-E, and FSE81. The safest check is to compare your original part number to 4006 710 2126 and confirm your trimmer uses the AutoCut 6-2 style head setup.
Q: Does this AutoCut 6-2 trimmer head come preloaded with line, and what line size should I use on an FS50C-E?
Most AutoCut 6-2 heads are designed to be loaded with your own trimmer line, so it’s a good idea to verify before installation if line is included. For the FS50C-E and the other compatible lightweight Stihl trimmers, use the line size recommended in your owner’s manual so the head feeds properly and doesn’t strain the drive system.
Q: I’m replacing the bearing housing on an FS38—do I need any special steps when installing this part with the new trimmer head?
When installing the 4144 640 5900 bearing housing, clean the shaft area first and inspect for worn splines or debris before fitting the new housing. After mounting the AutoCut 6-2 head, spin it by hand to make sure it turns smoothly and seats correctly, then recheck tightness after the first few minutes of use.
