I've got a Gammill longarm, but the guy who came and set it up and taught me how to use it talked to me about the tension on it. For the bobbin, he showed me how to check it by putting the bobbin of thread in the bobbin case and then holding the end of the thread in one hand and let the case go -- he said the bobbin case should descend like a spider going down -- not too fast, and not too slow, but like you would think a spider would. Once you get the bobbin tension right then it's a matter of getting the top tension correct. Loops on the back means the top thread is too loose. Thread breaking means the top thread tension is too tight. Good luck!