Black and Decker LSTE525 Weed Whacker Repair

 Recently, while using my weed whacker, a loud squealing sound and vibrations started from the motor. My initial thought was that a bearing or gear broke. The Instructables’ “Fix It Contest” is active, so it is a perfect time to repair it.

While this repair is for a specific model, the construction of most weed whackers is similar.  

Supplies

Tools

T15 Torex bit driver

#2 Philips screw driver

Materials

Machine Oil

PTFE grease

Step 1: Disassembly

 Using a T15 Torex driver, remove the 8 screws on the right side of the motor case. The is also one screw on the left side of the case.

Step 2: Disassembly Step 2

 The product label straddles the two halves of the case. Use a knife edge to cut the label along the joint of the two halves.  

Step 3: Disassembly Step 3

 The guard is held in place by a Philips screw and a plastic latch. After removing the screw, depress the latch and remove the guard.  

Step 4: Disassembly Step 3

 Removing the guard exposes three additional T15 screws to be removed.

Step 5: Disassembly Step 4

 Separate the two halves of the motor case to expose the motor and gear assembly. The pictures show a lot of debris inside the motor case.  

Step 6: Finding the Problem

 The motor and gears were cleaned as well as the inside of the case. An inspection of the gears showed no damage or excessive wear. Manually rotating the spool holder reveled the upper motor bearing and shaft squeaking.

Applying machine oil to both sides of the top motor bearing stopped the squeaking. Several cycles of applying oil to both sides of the top motor bearing and running the motor eliminated the squealing and vibration. Additional oil was applied to the various shaft and bearing locations.

During this cycling the motor was held in place by a strip of tape wrapped around the motor and the left half of the case.

Step 7: Reassembly

 The motor and gear assembly was positioned in the left half of the case. A layer of PTFE grease was applied to the gear teeth. The case halves are reconnected with the screws.

Step 8: Testing the Repair

 The repaired weed whacker was used for about 20 minutes confirming the problem was the top motor bearing.

I suspect that longer term the top motor bearing will fail completely because of the damage cause by the problem described above. Additionally, the weed whacker’s case has side and top vents that allow debris, dirt, and dust to enter. The motor’s body has side vents, which exposes the brushes and bearings to dust. The dust migrates into the sleeve bearings causing accelerated wear.