Overview
This aftermarket trimmer head kit includes the components needed to restore proper line feeding to your string trimmer. A malfunctioning bump knob or worn spring causes the line to stick or feed too freely, both of which reduce trimming efficiency. Replacing the head assembly is a quick fix that keeps your trimmer cutting cleanly.
Key specifications
- Replacement bump-feed trimmer head assembly
- Includes 4 piece(s)
- Tap-to-advance line feed mechanism
- Includes bump knob and internal spring
- Compatible with standard trimmer line diameters
Compatibility
This trimmer head is designed for Husqvarna string trimmers as listed above. Confirm the thread size and direction match your trimmer’s drive shaft before ordering.
Installation notes
With the trimmer off, lock the drive shaft and unscrew the existing head. Attach the new trimmer head, making sure the thread engagement is smooth and complete. Load the spool with the correct diameter trimmer line and confirm the bump-feed mechanism advances line properly before starting work.
Common questions
Q: Will this 537338701 bump knob fit my Husqvarna 128LDx trimmer head, or is it only for the 128L and 125L models?
Yes, this bump knob is compatible with the Husqvarna 128LDx as well as the 124L, 125L, 128L, 128LD, 128R, 223L, 223R, 322C, 323C, 325C, and 326Cx string trimmers. It is made to replace the trimmer head bump knob on those listed models, so if your original part number matches 537338701, it should fit correctly.
Q: How do I install this bump knob on my Husqvarna 223R trimmer head?
First, remove the trimmer head spool cover and take out any remaining line so you can access the worn bump knob. Thread or snap the new 537338701 bump knob into place the same way the original came off, then reassemble the spool and test the bump-feed function before use to make sure it advances line smoothly.
Q: My 128L bump knob wears down quickly from tapping on concrete edges. Will replacing it with this part restore normal line feed, and how can I make it last longer?
If the original knob is rounded off or cracked, replacing it with this 537338701 bump knob usually restores proper bump-feed operation as long as the spring and spool inside the head are still in good shape. To extend its life, avoid bumping on hard pavement when possible, keep the trimmer head clean, and inspect the spool for debris or line binding that can make you hit the knob harder than necessary.
