Thead tension or space is too loose - Euro-Pro 534DX Mechanical Sewing Machine

If you have your manual for this machine, look on pages 13-16, and check the troubleshooting guide on pg 20. Both explain quite clearly in pictures and words, with suggestions on what starting tensions to use for your project, and how to fine-tune your machine for the best outcome for your fabric..

If you don't have a manual, try this: set all four tensions to four, grab some fabric scraps similar in weight to what you're trying to sew, and test. Serge about 3 inches, check the front and back. If there are not two nice straight rows of what looks like straight stitching clearly placed away from the cut edge, then raise the dial on tensions 1 and two slightly and test until you find the correct setting. BE SURE TO WRITE IT DOWN as a calibrated starting tension for your machine. If the serger track is loose on top and there are not clearly defined, uniform loops on the cut edge, where the upper looper (tension 3) and the lower looper (tension four) threads meet AT the cut edge, then you'll need to loosen tension 3 or tighten tension four, or both.

I've scanned my manual and I'm trying to upload it tonight - it clearly explains, with illustrations, just how to fix the issue. I strongly recommend any time you start a new project, save some scraps of fabric to set your tensions with. I always do this, and I get great results. Let me know if you need more info.