On the back of the quilt my stitches often are loopy especially when I am doing curved lines. I suspect it is a tension problem but none of the adjustments I've tried has corrected the problem.
I'd appreciate any advice.
I find that when I quilt there is not a single, exact tension setting, but rather a small range in the settings that will produce good quality stitches.
When you see the thread on the bottom of your quilt sandwich, confirm that it is indeed the needle thread either being pulled to the bottom or never actually being pulled back to the top.
Most likely, your needle tension is on the low end of the 'range' of tension settings that will work nicely for your machine and current fabric, batting and thread choices.
So the first thing I'd do is increase the tension until just before it starts pulling the needle thread to the top. You'll need to tweak the tension, tweak and test, tweak and test, to determine the correct setting. Test on straight stitching because that needs to look good, too.
Then test on some curvy lines.
Especially when we're beginning to free motion quilt, we have the tendency to 'whip' around the curves...kind of like when we learn to drive.
Hey! It's fun! Why not?!!
Unfortunately, I think that the 'speeding up' around the curves affects the tension, pulls it out of whack...just enough to leave needle thread loops on the curves on the back.
These days, when I free motion quilt, I set my speed control to 60% for free motion quilting (my machine speed is set in 20% increments).
Once I'm warmed up, it feels a bit on the slow side, but I can always think faster than I stitch and seem to avoid having to rip out stitches where I lost track of the design.
With the foot control pushed to the floor, I can concentrate on creating a design (or following a drawn line) and keeping the quilt sandwich moving at an even speed. It's very Zen-like once you get the hang of it. (It definitely did take me some time to get used to going around curves at this slower, constant rate.)
The other benefit is that this reduced speed has cured needle thread loops on the back for curves...without tweaking the tension settings.
Hopefully one or both of these suggestions will work for you. Please let me know how it goes.
Readers, if you have suggestions or have solved this problem yourself, please share your experiences with the 'comment' link found below. Thank you!