Skipping stitches at higher speeds
I picked up this Singer 15-90 and wanted to make it a hand crank, which I just finished setting up, because the only real sewing I do is small repairs, things like that. It's easier to put this machine on a table than set up a machine in a cabinet, move it to an outlet with good light... Anyway, when I tested this it worked fine at slow speeds, but if I cranked it pretty fast (not as fast as a motor would turn the machine) it skipped stitches completely and the top thread ran from the last stitch to wherever I stopped, as did the bobbin thread.
Is this a bobbin tension issue? Top tension issue? I didn't take either tension mechanism apart. Something else?