Hi - you might have a dirty bobbin case, or need a new one. IAfter awhile, little teeny dust bunnies can collect in your bobbin case and cause your bobbin tension to go wonky, especially if you use cotton thread. If you happen to have an extra bobbin case, try using the new bobbin case to see if that solves the problem. Otherwise.....
In general, you should oil your machine as indicated in your manual as often as directed. You should change your needle every 10 hours of sewing - or each time you start a new project, and you should take your machine in for service every one or two years - even if you only use it once and awhile.
- Remove your bobbin case and take out the bobbin. Find a small, stiff brush like the one that came with your machine and stand in very good light. Brush out the inside of your bobbin case, and push one or two bristles of your brush into any opening you can see. If you see any trace of dust but you can't get it out, use tweezers to gently pull the dust out. Now look at the outside of your bobbin case. In the small opening where you insert your bobbin thread into the bobbin case, there is a small piece of metal with screws in it the lays over the bobbin case. Brush that area carefully, and again, insert one or two bristles under than piece of metal and into any other small opening where the bristles will fit. Try sewing again. If you are still getting loops, take out your bobbin case with the bobbin thread still inserted and grab the bobbin thread with two fingers. Let go of the bobbin case - sort of like you are holding a yo-yo. If the bobbin case starts to drop as soon as you let go, your bobbin tension is loose. If the the case doesn't move, gently snap the bobbin thread you are holding and see how far the bobbin case moves down toward the floor (you might need to try this a couple of times, the bobbin has a nasty habit of flying out). When you do the snap, the bobbin case should move down about two inches and stop. If do not know how to adjust the bobbin tension, either check your manual or take the machine in for service.
- If you haven't already, it's a good idea to remove the thread plate that sits under the needle and clean that area out with your brush. Also, get a really good flashlight and check the area where you insert your bobbin case. Gently turn your fly wheel and look inside the hook area - remove any dust or bits of thread.
Hope this helps, Ginny