Jim, I am going by the info in the manual that says "Needle thread lies straight along tip side of material, caused by too heavy tension on needle thread or too light tension on bobbin thread..." That's why I have tried both reducing needle thread tension and tightening bobbin tension (in about 1/8 turn increments each time and then doing a test sew). The leaf spring appears to be undamaged. Has no buildup and seems to work correctly when the adjusting screw is is loosened/tightened. Yo yo tested and bobbin only barely drops. Both top and bottom thread are brand new spools of Gutermann 100% cotton.
Candace, the bobbin case is threaded exactly as the book shows. When I hold the bobbin in my right hand, the thread comes over the top toward me. The bobbin case latches securely when put on the stud. And the position finger is in place in the notch of the position plate.
Keep the ideas coming. I'm taking the time to look at the manual's illustrations and double checking everything before I answer your questions.
SewButch, I have the user's manual and even found and printed out the adjuster's manual. Okay, I'm off to disassemble the needle thread tension assembly. Wish me luck!
Dorothy in Denver