There could be several reasons why the upper thread keeps breaking.

• The upper thread could be installed incorrectly.
  Rethread the machine according to the instructions.

  For details, refer to "Upper threading".

  
   
• The upper thread tension could be set too tight.
  Set the tension to the best thread tension setting or less.
   
• Make sure the spool of thread is installed correctly using the correct size spool cap for the size of spool.

  For details, refer to "Place a spool of thread on a spool pin".

  
   
• Make sure the needle is correctly inserted with the flat side facing the back and pushed up into the machine as far as possible.
   
• The needle could have been damaged or bent.
  If so, replace with a new one.
   
• The lower thread tension is incorrect.
  The thread does not roll out of the bobbin case smoothly.
  Adjust the lower thread tension.
   
• The bobbin thread is not wound correctly.
  Check that the bobbin is wound so that it about 80% full and that the thread is evenly wound.
  If the bobbin is not correctly wound, rewind the bobbin.
   
• The thread density of the embroidery data is too fine.
  Three or more overlapping stitches are being sewn.
  Using a data design system, correct the thread density and overstitching settings in the embroidery data.
   
• The embroidery data contains stitches with a pitch of zero.
  Delete all stitches with a zero pitch.
   
• The embroidery data contains many stitches with an extremely small pitch.
  Delete all stitches with a small pitch.
   
• The fabric is not taut.
  Firmly set the fabric in the embroidery frame so that it is taut.
   
• The thread is loose in the hook area or the hook does not rotate smoothly.
  Remove the loose thread.
   
• The thread quality is poor.
  The thread quality is too weak due to age of thread.
  Replace thread.
   

  Remove any knots or tangles.

  
   
• A bobbin designed specifically for this machine is not used.
  Be sure to use the correct bobbin.
• Needle and thread are incorrect.
  Be sure to use the correct thread and embroidery needle.

* In the cases shown below, consult nearest authorized Dealer or Service Center.
 

• The area around the hole in the needle plate is damaged.
   
• The needle hits/touches the needle plate.
   
• The presser foot is set too high and not correctly positioned. The needle hits/touches the presser foot.
   
• The area around the embroidery foot hole is damaged.
   
• Sliding surface on hook race is not smooth.
  There are scratches or burrs on it.
   
• The play between the hook and the race is too much.
   
• The space between the hook stopper and the hook cannot be adjusted.
   
• The automatic needle-threading mechanism is broken.