Working with the machine on a thin jersey fabric the unreliable tension setting became untenable. Had previously diagnosed the issue. Last week I took apart the entire tension assembly. That's a nice thing about simple machines--it's easy to disassemble them! 

Dial, washers, springs, the groove wheel and screws were set aside in the order they were removed to streamline re-assembly. Replacing the lever that clicks into the grooves on the ratchet wheel (which compresses the springs as it moves along the tension axle) was baffling. (It's the wide white disk, photo right).

Left the machine overnight and today approached it anew. Figured it out! The tension is perfect now. I've been jury rigging it for ages. This is great!

Machine Fix

Green Arrow: Tension Dial; Blue Arrows: Screws
For awhile the tension on this machine has been out of commission. Winding the thread around the bobbin screw is an imperfect fix. Figured the spring that puts pressure on the tension disks might be the culprit. Today took the machine apart to find out.

After unscrewing four screws, removed the tension assemblyIt looked fine. The tension is as faulty as ever, but now I know what is wrong I think. Will take it apart once more and see...

Setting Tension: By turning the tension dial on a sewing machine the coils of the spring are compressed. (Ignore the number facing the camera; in actuality the highest tension corresponds to the highest number on the dial and the loosest tension is zero.)
Tension Assembly: Highest Tension
Tension Assembly: Lowest Tension,