Originally Posted by path49

Somewhere between the knob & where it connects to the feed dog mechanism (usually closer to the knob), there is probably an eccentric that controls the stitch length. It will look like a normal screw head & you'll more than likely have to loosen a nut to turn it. Loosen the nut just enough to turn it a little, tighten & check your stitches.

I just adjusted the stitch length on a Kenmore 158 series machine & that was the set up on it. I first turned the dial to the longest stitch (6 spi on mine)...moved the eccentric a bit at a time & kept checking the length. When I was getting a perfect 6 stitches, I turned the dial to 0 to make sure that the fabric wasn't moving. Actually, I was stitching on paper (without thread)....it was easier to check the holes to count the stitches & make sure it was stitching in the same hole on 0.