BREAKING NEEDLES? Make sure your needles are correctly offset?
Flat back of needle parallel to back of machine?
Schmetz 90/14 size Universal needles come loaded in the serger from the factory, other sizes of needles work, but not larger 90/14, and have you verified that both left and right are same exact size? (don't laugh, people do all kinds of things)
Do not attempt to use Jeans or Denim needles in the serger.
Use the right needle for the right type and weight of fabric:
Universal Needles are for use with woven fabrics like quilting cottons, etc.
Stretch needles and jersey needles are used with knit fabrics.
You can download the Schmetz Needle app for handy use in your Android phone or tablet https://play.google.com/store/apps/details?id=com.schmetz.needle
Bulk needles can be purchased via Amazon.com, Wawak.com and HomeSew.com