I disassembled the entire bobbin case and it actually was pretty clean, but I cleaned every last bit and oiled and reassembled. The bobbin tension could probably be a little looser, but it's hard to tell for sure since I can't get it to sew. I have the needle in with the flat side to the left and threaded right to left. The problem with stiffness in the wheel occurs even with the machine completely unthreaded.