Janome, the manufacturer of New Home sewing machines, recommends trying to adjust the upper tension by turning the tension regulator dial before changing anything on the bobbin tension. However, if adjusting the upper tension does not correct the problem, Janome recommends removing the bobbin case and pulling on the thread end. The thread should not come out too quickly and you should feel a slight, smooth tension when you pull the thread. When the thread comes out of the bobbin case too quickly or not at all, you need to adjust the bobbin tension.
Remove the bobbin case by raising the needle to its highest position, then lift the hinged latch on the bobbin case and pull straight out.
Locate the thread tension regulator screw. It will be the screw located closest to the thread slot.
To tighten, or strengthen, the bobbin thread tension, hold the case so you can see the bottom of the bobbin, and turn the tension regulator screw clockwise with the precision screwdriver.
To loosen, or weaken, the bobbin thread tension, turn the tension regulator screw counterclockwise with the precision screwdriver.
Check to see if the adjustment is correct first by pulling on the thread end. If the thread pulls out with a smooth, even tension, test again by sewing a few inches on a fabric scrap.
To determine whether the bobbin tension needs to be tightened or loosened, sew a few inches on a piece of fabric, then look at the stitches. If the loops are sticking up through the fabric from the bottom, tighten the bobbin tension. If the top thread is pulled down through the fabric and the bobbin thread resembles a piece of thread laying on the fabric instead of stitches, loosen the bobbin tension.