The LST300 is the trimmer many small-yard owners leave hanging in a shed until the line snaps at the worst possible moment. The AFS head is convenient when it is clean and loaded correctly. It is frustrating when old debris, brittle line, or a tired cap make the feed inconsistent.
Before you open the head
Remove the battery and set the trimmer on a patio table or bench where the head is easy to reach. Brush packed grass away from the cap tabs before you squeeze them. Many broken caps start with forcing the latch over dried clippings.
If the spool cavity is dirty enough to keep the spool from sitting flat, clean that before you install fresh line.
What to match
For this class of trimmer, check:
- The spool shape and hub fit.
- The line diameter the head expects.
- The feed direction molded into the spool.
- The condition of the spring and cap tabs.
An almost-right spool is still wrong if it sits high or wobbles in the head.
Reload or replace
If you are using a pre-wound spool, route the line through the eyelet before snapping the cap on. If you are winding fresh line, keep the wraps tight and even so the AFS mechanism can release it cleanly.
First-yard test
Run the trimmer over open grass first, not along a fence or curb. Listen for smooth feed and even motor note. If the line dumps too quickly or binds immediately, reopen the head before the fresh line is shredded by hard edges.