Miriam is correct - the 301 threads right to left so the needle is inserted with the flat side to the left. The first thing I would do is take the bobbin assembly apart and clean it. Remove the two screws in the bed of the machine from the top, then the bottom parts will come out. When reassembling, the little finger has to be upright to fit into the slot in the plate or the machine won't sew. I found my manual free online.