rryder

It's the dial to the left of the area where you put your thread spool. Don't change it too much at once, or you may have a problem with your top thread breaking. On my PC420 I usually had to lower my top thread tension a little from the normal setting of 3 or 4, but since you are having the problem on the back side it looks to me like you need to raise your top thread tension. Try raising it just one or two small clicks at a time until you've got the worst of the eye lashing gone. Then you will want to practice speeding up the machine but slowing down your hands as you go around curves.

Rob