Janome AirThread 2000D Professional Service Bulletin page 65

Adjusting the Tension
When either upper looper tension is too loose or the lower looper
tension is too tight, or both, the upper looper thread is pulled to

the bottom of the fabric. To correct this, turn the upper looper
tension dial to a higher number or turn the lower tension dial to a
lower number, or both.
When the right needle tension is
loose, you will notice these loops

on the bottom of the fabric. To
correct loose right needle tension,
turn the right needle tension to a
higher number.
65