Replace the cutting-line spool
Fit a factory-wound AF-100, route its single line through the eyelet and record the cap check before use.
Version 2.0.0. Required observations are marked *. Your answers stay in this browser.
1. Match the model and parts
Remove the battery. Find LST300 and the adjacent type number on the tool label. Compare the guard, cap, spool and assembly figures with the linked LST300 manual. Use ServiceNet for your exact type if they differ. LST300 is not a bump-feed head.
Region: US
Parts: Automatic-feed head with AF-100 spool; match model and tool type to manual
Not covered: LST420 / LSTE525; GH corded models; Dual-line heads; Metal line or blades; Nonmatching tool type or modified head; Unknown tool type or missing exact-type manual; Bump-feed conversion.
Choose the versions you can confirm.
Compare versions →2. Prepare
Keep the battery removed if the exact type/manual match is unknown or parts differ from the figures. Stop for a damaged battery, exposed wiring, a faulty switch, cracked guard, broken spool/hub, damaged cap tabs or housing slots. Use an authorized service center. Never open the battery, motor housing or charger.
Consumables and fit
| Item | Specification & fit | Do not substitute |
|---|---|---|
| Factory-wound replacement spool | BLACK+DECKER AF-100; 0.065 inch (1.65 mm) round nylon monofilament Original LST300 automatic single-line head, after exact tool-type/manual match | Bump-feed or dual-line heads; metal, serrated or heavier line; unverified replacement headsEnglish p9 Cutting line / Line feeding; Replacement accessories |
| Replacement spool cap | BLACK+DECKER RC-100, confirmed against the exact tool-type parts list Original compatible AF-100 housing with undamaged slots | Damaged housing; caps with different tabs; forcing an apparently similar partEnglish p9 Cutting line / Line feeding; Replacement accessories |
3. Follow your checks
Match the model and preparation to start.
Read all possible routes
Is the battery removed, the trigger released and the cutting head stopped, with no battery damage, exposed wiring or faulty switch?
- Yes — Keep the battery removed for every hands-on step.
- No — Stop using the tool for electrical, battery or switch damage. If you have only omitted battery removal, make the tool safe before restarting.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Have you matched the label LST300 AND its exact tool type to the official lookup manual and its figures, with the original AF-100 automatic single-line head?
- Yes — Record the label type and matching manual reference in the first step.
- No — An unknown type, unavailable type manual, different figures, bump-feed head or dual-line conversion blocks this procedure. Use manufacturer support to identify the correct instructions.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Does the replacement package identify AF-100 and 0.065 inch round nylon line?
- Yes — Use the factory-wound spool after confirming the type match.
- No — Use Check the replacement line specification before opening the head.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Are the guard, cap tabs, housing slots and visible feed lever intact?
- Yes — Work with the removed battery beside the tool.
- No — A replacement spool cannot repair damaged retaining parts.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
4. Follow and record
Complete the checks before recording physical work. Follow steps in order.
Record the exact tool and make it safe
Release the trigger, let the head stop, engage the lock-off and remove the battery. Leave it removed throughout hands-on care. Keep fingers away from the sharp cutter on the guard. Read LST300 and the tool type from the label. Open the official model/type lookup and compare its manual and parts figures with your actual guard, single-line head and AF-100 spool. A readable model name alone does not establish the type. If the exact type manual cannot be obtained, or any figure differs, save a preparation record and stop.
Look for: The battery is physically separate from the tool; your label type and matching manual reference are written below.
Manual: Official model/type lookup instructions; type is beside or below the model numberRelease the cap and lift out the spool
Squeeze both cap tabs and lift the cap from the housing. Hold the housing with one hand and draw the old spool out with the other. Keep the parts together; avoid pulling on the feed lever.
Look for: The cap and spool separate without a pry tool; both tabs remain intact.
Manual: English pp9–10 Replacing the spool; figs M–OClear and check the empty housing
Remove loose grass and dirt from the spool and housing. Find the central boss and the lever shown in fig N. If the lever has moved, refit it only when its pictured position is clear; otherwise stop for help.
Look for: The boss is clear and the lever matches fig N without being forced.
Manual: English pp9–10 Replacing the spool; figs M–OThread the one line exit
Release the new spool line from its transport hold and pass that end through the housing eyelet shown in fig O. Keep the line outside the rim where it exits; do not trap it beneath the spool.
Look for: One nylon line passes through the eyelet, with no second outlet or doubled strand.
Manual: English pp9–10 Replacing the spool; figs M–OSeat the spool on its boss
Push the spool onto the central boss and turn it slightly until it settles. Arrange approximately 5-3/8 inches (136 mm) of line outside the housing. Keep the lever in its documented position.
Look for: The spool sits down in the housing; it does not rock above its seat.
Manual: English pp9–10 Replacing the spool; figs M–OLatch the cap and limit the line
Align both cap tabs with the housing slots and push until securely snapped in. Check that both sides hold. If nylon extends past the guard cutter, use scissors to shorten it so it only reaches the blade; keep hands away from the blade.
Look for: Both tabs retain the cap and no line is trapped under its rim or extends beyond the cutter.
Manual: English pp9–10 Replacing the spool; figs M–ORecord the refit before returning to use
Keep the battery out while you record the spool identity and cap result. Finish Verify the trimmer after maintenance before any normal-use test. A cap that lifts or a spool that will not settle needs the cap-latch check or service.
Look for: The record describes the fitted part and a secure cap; operating performance is still untested.
Manual: English pp9–10 Replacing the spool; figs M–O
5. Keep your result
Record what you observed. A completed checklist does not certify that equipment is repaired.
When to check again
Spool empty or insufficient usable line remains
Inspect when the stated condition occurs. The manual gives no fixed day or month interval.
Manufacturer guidance · English pp9–10 Replacing the spool; figs M–OSources & fit
- BLACK+DECKER LST300 instruction manual (manufacturer document, retailer-hosted)English pp9–10 Replacing the spool; figs M–O · Checked 2026-10-13
- BLACK+DECKER: locate a manual using model and type numberOfficial model/type lookup instructions; type is beside or below the model number · Checked 2026-10-13
- BLACK+DECKER LST300 product and supportLST300 model identity; Automatic Feed Spool; Includes AF-100 · Checked 2026-10-13
Independent, AI-assisted guidance. No physical repair trial is claimed. Manufacturer instructions for your exact version take priority.