If you take the spring off you will need to reset the tension. resetting the bobbin tension may go a long ways to fixing your problem. Tammi has some good info here:
http://www.archaicarcane.com/bobbin-...obbin-tension/
she explains it much better than I can. It is easy to do. It would be where I would start. I didn't mean to insult you - the pics just look kind of dried oil colored. I know some times a light coating of dried up oil will keep things from moving correctly. I would also wind a new thread on a new bobbin to make sure everything is in good order. Then I would put in a new needle. Make sure the needle in in the right direction. The flat side goes away from the machine - grooved side toward the machine. Then thread from right to left. Use a good spool of thread. I had fits one day when I used an old spool of thread and the thread caught on a rough place. Tammi also has good info on the upper tension on her same web page. Check that out as well. Keep posting and we will see what will work for you.