How to Replace a Toro 88616 Pre-Wound Spool (51831 / 51831T Flex-Force 60V)

The Toro 88616 is a 3-pack of pre-wound spools (88615 is the single) with 2 mm (0.080 in.) line for the Flex-Force 60V 13”/15” string trimmers. This is a dual-line bump-feed head: the cover and spool come off together, and the two line ends leave through two holes in the cover.

Toro’s manual (“Replacing the String”, pages 16–17) is written for rewinding bulk string. With a pre-wound 88616 spool, the winding steps (4–7) aren’t needed — you go from removing the old spool straight to fitting the new one. That shortcut is our reading of the manual; Toro doesn’t spell it out.

Steps from Toro’s manual (for a pre-wound spool)

1. Remove the battery pack and clean any debris from the trimmer head.
2. Press the tabs on the side of the trimmer head at the same time and remove the cover and spool.
3. Remove the spool from the cover.
4. Install the new spool into the cover and route the ends of the string through the holes in the cover.
5. Fit the spool and cover assembly back onto the trimmer head and push until the cover tabs snap into place.

Toro’s own numbering is 1–3 and 8–9; its steps 4–7 cover winding bulk string (below).

Line and parts

Toro says to use only 2 mm (0.080 inch) monofilament string — its part 88201 — or the pre-wound spools 88615 (single) and 88616 (3-pack), and warns that any other gauge or type can damage the trimmer. Toro’s parts lookup lists the 88616 for the 51831, 51831T and 51834T, but only for some serial-number ranges — check your trimmer’s serial number there before ordering.

To feed line in use, tap the bump button on the ground.

Refilling with bulk string instead

Cut one piece of 2 mm (0.080 inch) string about 3 m (10 ft) long, bend it at the midpoint and push the bend into the starter slot in the center rim of the spool until it snaps in. Wrap both halves evenly and firmly — clockwise when you look at the bottom of the spool — leave just enough to reach the swath blade, and snap the ends into the guide slots on the spool. Then carry on with step 4 above.

Sources: Toro Flex-Force Power System 13in/15in 60V MAX String Trimmer operator’s manual, models 51831 and 51831T (Serial No. 320000001 and up), Form No. 3440-153 Rev D, “Replacing the String”, pp. 16–17, and line-feed note, p. 14 (PDF from toro.com); Toro parts lookup for the 88616. Checked September 25, 2026.