Troybilt TB22 String Trimmer and the Flying Bump Knobs

unit91

Member
Joined
Aug 11, 2019
Threads
2
Messages
27
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
Here's mine. 20190819_190416.jpg20190819_190327.jpg
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,867
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
Outer housing looks like it is in good shape. String spool looks like it is getting chewed up,
 

unit91

Member
Joined
Aug 11, 2019
Threads
2
Messages
27
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
Ordered a new spool. We'll see what happens. Thanks.
 

unit91

Member
Joined
Aug 11, 2019
Threads
2
Messages
27
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
Outer housing looks like it is in good shape. String spool looks like it is getting chewed up,

Installed new string spool with string, and new bump knob. Bump knob flew off after about 10 seconds, just like before. Is the bolt in the bump knob supposed to turn freely inside the knob or remain fixed?
 
Last edited:

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,867
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
It should be a square headed bolt inside the bump knob, and if it turned you couldn't screw it on.
 

unit91

Member
Joined
Aug 11, 2019
Threads
2
Messages
27
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
It's as you described it. Bolt doesn't turn. Any chance it could be the string?
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,867
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
I don't think it is the string. The only other thing I could think is could be is the threads in the shaft where the bump knob screws into is worn, and loosing friction preventing the knob from properly tightening down. Something else to look at is make sure the internal thread cavity is clean. Maybe grass built up or something else causing a bottoming out effect.
 

unit91

Member
Joined
Aug 11, 2019
Threads
2
Messages
27
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
Thanks, I'll check.
 

Jake8131

Active Member
Joined
Nov 17, 2017
Threads
6
Messages
52
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
Sounds like the threads on the shaft that the bump knob screws into are stripped.
 

unit91

Member
Joined
Aug 11, 2019
Threads
2
Messages
27
  • / Troybilt TB22 String Trimmer and the Flying Bump Knobs
If I take the string spool off and run it with just the bump knob installed, the knob stays on at all speeds.
 
Top