The tension dial over above the needle looks pretty dirty, and not too complicated. The dial in your picture looks like the stitch length regulator? Over by the pillar on the bed of the machine, but I've never seen a 101 in person.

That is a picture of the the feed regulating shaft and associated parts. It is what most of us call the stitch length assembly. It is located on the right side of the bed of the machine near the pillar.

It looks like you have already taken the tension apart as seen at https://www.quiltingboard.com/attach...37-singer1.jpg

Janey - Neat people never make the exciting discoveries I do.

This is a correction to my original post.

The stitch length is what i was talking about. I really need to proof read my post before I submit.