sdeaaz

I used a machine at our quilting group one day that did this... the bobbin was upside down.... try that....

shelrox

Thread not threaded correctly, bobbin in backwards, need a new needle, wrong bobbin, humm what else? But those are the main reasons this usually happens. And dont forget always when in a hurry and a time line is approaching it has to happen.

margecam52

All of the suggestions so far are valid ones to keep in mind. Also remember to clean the bobbin hook area, bobbin case and anywhere else lint/stray thread may be hiding in. If this is the back of the quilt... then do make sure to put the hopping foot down...believe it or not...99.9% of all quilter's have left that foot up at one time or another. Most will tell you that you need to tighten the upper tension (hence check that the foot is down)...the usual rule of thumb is if you get loopies like this on the underside...it's the upper tension to loose...if they are on the top...the bobbin is too loose....but that is not always the rule.
I check my tension manually. I like to run all my threads fairly loose...for the top tension...I thread the machine, put the hopping foot down...and pull on the thread coming off the needle...the needle may hint at bending/flexing, then should straighten out and the thread should pull out straight and steady, no jerking and with some tension but no so much the thread breaks or the needle stays flexed.
Once I have that (and every thread is different, even color can make a difference) upper tension adjusted (righty tighty, lefty loosey)...I test the bobbin.
To check the bobbin manually, I lay the bobbin case (loaded with a full bobbin) upright (you can see the bobbin in the case) in the palm of one hand, and pull on the thread coming out of the case. The case will start to come off your hand, but will then stop and the thread will pull out straight and smooth...with just a hint of tension.

This bobbin test works the same as the one where you hold the loaded bobbin case above one hand and holding the thread, let the bobbin case go...it should slowly drop...like a spider on a web down to your hand.

I then test the stitches...I do this by stitching on a small scrap on the side of the loaded quilt. Couple of stars and circles...and the tension should look great..if loopies on the underside...you can tighten the upper half to one full turn and retest...if pokies...make sure they are pokies...run your fingernail over them...if you can't feel the pt pt pt of the pokies...they aren't pokies. If you can feel them...either loosen the bobbin 1/12 of a turn on the screw...or tighten the upper a half turn. If the upper thread breaks, back off a full turn and adjust the bobbin screw 1/12 of a turn (lefty to loosen).
Once you have a great stitch...you are good for that quilt/thread...you WILL have to make adjustments depending on the quilt fabric, batting, thread...it's normal to do so.
If you get a great stitch going & have the towa gauge for the bobbin...test the bobbin and jot that number down...then after that, no matter what size/type thread you put in that bobbin...you know the number you want that bobbin to test out at.

bmorawitz

That happens when the pressure foot is not down or the thread has come out of one of the loopers or tension on your machine..... if it is on the bottom of fabic it is the top trension... try rethreading your machine and if your going real fast the thread is looping around something it should not have... Mine does that when the thread loops around the tension because I am sewing tooo fast for the machine....try that and see if it helps.... loopy on top is your bobbin thread

quiltapillow

I was having a similar problem with my Janome and took it to a repairman. he said : look here you somehow inadvertedly moved your tension and showed me how to mark with a marker and watch my tension. He said it happens and you may not realize reaching over or someway or the other it just did get out of sink.

duckydo

Usually if you have loops on the back it is your top tension, if you are getting loops on the top it is your bobbin tension. I have a gammill and that is what it is with the longarm. Hope you get it figured out, tension can be a real headache.

Jingle

Forgetting to lower the presser foot is why mine looks like that. It is easy to forget.

0tis

Definitely tension issue - usually this is my top tension - I rethread and sometimes I have to clean out the tension discs on top - sometimes mine get lint buildup and I will carefully unscrew the discs and clean the fuzz out. Its frustruating but you will find it.