/diy/ - Do It Yourself

Sup, /diy/. Anyone here got particular expertise with regard to old sewing machines? I picked one up at a flea market, after some extensive cleaning/reoiling and replacing a few moving parts, I've got it functioning great. Sewing forwards, it works like a motherfucker, really strong and a good stitch.

However, when I try to backtrack or sew backwards, it does >pic related. pulls the bottom thread all up in big loops, the top thread just runs flat on the surface. Its 100% unusable, and its really frustrating me.
I've tried fucking with the upper tension, making it both high and low, with no real effect. I don't know enough about the mechanics of these older machines (and the mechanics of it sewing in reverse) to do a whole lot of troubleshooting beyond that.

Anyone help me out?