This is about longarm tension, but I found some of it helpful even though I don't have a longarm. However, prodding around in the tension mechanism with a pin seems risky to me. You don't need a scratch or burr there! A lot of machines don't have the separate bobbin case, but still the ideas about how to tell if the tension is balanced and not too tight seems useful. Your manual should have specific information for your machine.
http://www.youtube.com/watch?v=Q1mRhcquZTM
FroggyinTexas, your comment reminds me of something my DH mentioned from his childhood in the 1950's in the Panama Canal Zone. A man with a push cart would walk through their neighborhood shouting "Fix! Sawn Msheens!", and it was a long time before he figured out what the man was saying. Where's the "Fix Sewing Machines" guy when we need him around here!