Craftsman V20 Weed Wacker String Replacement

Craftsman V20 Weed Wacker String Replacement

If your Craftsman V20 weed wacker has stopped feeding line or the string is worn down to a nub, don’t sweat it. Replacing the string is quick once you’ve done it once or twice. I’ve been trimming edges and fence lines with the V20 platform for seasons now, and in this guide I’ll walk you through the exact process I use, along with pro tips to make the line last longer and feed reliably.

What You Need Before You Start

String trimmers are simple tools, but a few details matter. Gather these before you begin:

• Correct replacement line or pre-wound spool for your Craftsman V20 model
• Clean cloth to wipe dust and grass from the head
• Scissors or snips to cut line cleanly
• Safety glasses and gloves

Most Craftsman V20 string trimmers use either 0.065 in or 0.080 in line. Check your user manual, look at the label molded into the trimmer head, or reference your model number. Craftsman pre-wound spools are commonly labeled CMZST065 (0.065 in) and CMZST080 (0.080 in). When in doubt, match what came with your trimmer originally.

Gardener’s note: My 13-inch V20 trimmer handles 0.080 in line beautifully for thicker weeds, while smaller/light-duty models usually prefer 0.065 in for smoother feeding and longer runtime.

Safety First Every Time

• Remove the battery before touching the head. This is non-negotiable.
• Let the head cool if you’ve just been trimming — friction warms the spool.
• Work on a bench or a patch of lawn so small parts don’t disappear.

Two Ways to Replace the String

You can either pop in a pre-wound Craftsman spool or wind bulk line onto your existing spool. Pre-wound is faster; bulk line is cheaper and lets you choose premium materials.

Replacing with a Pre-Wound Craftsman Spool

This is the fastest option:

• Remove the battery.
• Flip the trimmer over and press the tabs on the spool cap to release it. Some caps twist off instead — follow the arrows on your head.
• Pull the empty spool straight out, noting how the old line exits through the eyelets.
• Seat the new pre-wound spool so the line ends feed through the eyelets in the trimmer head.
• Snap or twist the cap back on, ensuring it fully locks. Tug the line ends to confirm they’re secure.
• Reinstall the battery, tap the bump head on the ground, and run the trigger briefly to advance and even out the line length. Trim any excess to the line-cutting blade on the guard.

Quick win: Keep a spare pre-wound spool in your garage. When the first runs out mid-trim, swap in seconds and rewind the empty one later.

Refilling the Existing Spool with Bulk Line

If you want to save money or prefer a particular line, refill the spool yourself. Most V20 heads are dual-line with two channels on the spool and two exit eyelets.

• Remove the battery and release the spool cap.
• Clean out grass dust from the head and spool. Debris causes jams.
• Check the spool for arrows indicating winding direction. Follow them exactly.
• Cut your line to length. A safe starting range is 12–20 feet total for dual-line heads, or as printed on your spool. Too much line causes jams; too little runs out fast.
• Find the anchoring notch or hole(s) in the center of the spool. If it’s a dual-channel spool, cut two equal lengths or fold a single long length in half (if the design allows) to share both channels evenly.
• Anchor the line end(s) and wind the line tautly in neat, side-by-side rows, following the arrows. Don’t cross over itself or leave gaps. Leave 4–6 inches free on each end.
• Lock the loose ends in the holding notches on the spool rim to keep them from unraveling.
• Thread each line end through an eyelet in the trimmer head.
• Seat the spool back into the head, keeping tension so the wraps stay snug. Release the ends from the holding notches once in position.
• Reinstall the cap securely. Reinsert the battery and bump-feed to equalize line length to the cutter on the guard.

Pro tip: If your line is springy or kink-prone, soak it in water for 24 hours before winding. Hydrated nylon is more flexible and feeds more consistently.

Choosing the Right Line for Your V20

All trimmer line isn’t created equal. Here’s how I pick for my Craftsman V20:

• Diameter: 0.065 in for light grass, edges, and longer battery life. 0.080 in for thicker weeds and longevity on fences and curbs. Match what your head supports.
• Shape: Round line feeds most reliably. Twisted or star-shaped line cuts cleaner and quieter but can snag if poorly wound.
• Material: Copolymer or commercial-grade nylon lasts longer against concrete and chain-link. It’s worth the small premium.

My go-to: A quality 0.080 in copolymer twisted line for fence lines and driveway edges — it outlasts budget round line by a mile.

How the Bump Feed Should Work

The Craftsman V20 head typically uses a bump-feed system. With the trimmer at speed, gently tap the head on the ground and the spool releases a short length of line. A cutter on the guard trims it to the safe maximum. If bumping doesn’t release line, you’ve likely got a winding, cap, or debris issue — see troubleshooting below.

Common Mistakes I See (And How to Avoid Them)

• Overfilling the spool: Leads to jams and poor feed. Stick to the length molded into the spool.
• Ignoring winding direction: The arrows matter. Reverse-wound line won’t feed.
• Crossed or loose wraps: Keep the line snug and neatly layered. Crossovers weld under heat and friction.
• Mismatched diameter: Too thick for your head = jams; too thin for tough jobs = constant breakage.
• Running the line too short: The head needs enough free line to bump-feed. Keep 2–4 inches outside the eyelets before the first bump.

Troubleshooting Feed and Breakage

Line Won’t Advance When Bumped

• Open the head and check for grass dust packed inside. Clean thoroughly.
• Ensure the spool cap is snapped on fully — a loose cap locks the spool.
• Inspect the line for melted spots or kinks. Rewind neatly, or replace if fused.
• Verify the winding direction and that each end exits the correct eyelet.

Line Breaks Constantly

• Step up to a heavier line if your head allows (e.g., from 0.065 to 0.080 in).
• Reduce throttle near hard edges. High RPM against concrete chews line fast.
• Check the guard blade. A dull or bent cutter can nick the line.
• Use a tougher copolymer line for abrasive spots.

Head Vibrates or Feels Unbalanced

• Ensure both line ends are equal length after bumping.
• Rewind the spool evenly; a lopsided wrap causes wobble.
• Replace a cracked or warped spool. Heat and impacts can deform plastic over time.

Maintenance Habits That Pay Off

• Blow out the head after each session — dry debris is friction fuel.
• Store spare line in a sealed bag with a damp paper towel to keep nylon supple.
• Keep a fresh, pre-wound spool in your toolbox for mid-trim swaps.
• Inspect the bump knob and cap tabs each month; replace at the first sign of wear.

Quick FAQ

How often should I replace the string?

It depends on what you’re trimming. Light lawn edges might use a few feet per month; fence lines and gravel drives can eat a spool in a couple weekends. I reload as soon as bump-feed gets inconsistent.

Can I mix line types on the same spool?

It’s best not to. Mixing diameters or materials can feed unevenly. Finish one type, then load fresh matching line.

Is thicker always better?

Only if your head supports it. Thicker line resists breakage but can reduce runtime and strain the trimmer if oversized. Stick to what Craftsman specifies for your model.

Final Thoughts from the Yard

Once you’ve done a Craftsman V20 weed wacker string replacement a couple of times, it becomes a five-minute pit stop. Keep the head clean, wind the line snug in the right direction, and choose a quality line that matches your model and your yard’s challenges. Do that, and you’ll spend less time fiddling with the spool — and more time enjoying those crisp, clean edges that make the whole landscape pop.