K, just a quick one before I go to bed, then I'll think on it a little more:
1. Here's bobbin case dis-assembly, on a FW case, so it's identical. Bonus
http://www.archaicarcane.com/tear-it...e-maintenance/
2. I like Jamie Wallen's troubleshooting for bobbin cases and tension problems as well, it goes a step further than my blog does, and if you use the pin like he does, you might get away with not disassembling. It's for longarms, but works perfectly fine for domestics as well:
http://www.youtube.com/watch?v=Q1mRhcquZTM
3. I have noticed that there are a lot of things not mentioned in upper tension rebuild instructions. Try these videos (mine) that I did last week. It's a 201, but the internals and operation should be identical. The first 2 videos cover some slightly different things (I expand more on some things than on others in each) which makes them both worth watching.
http://www.youtube.com/watch?v=guYToL6Gegs - ON Machine
http://www.youtube.com/watch?v=kzFXRdNE_1s - Off machine assembly
http://www.youtube.com/watch?v=WxtQO2XSB4s - Fast tension test (This is a visual of what I describe on my blog)
4. Try changing the bobbin you're using. Wind another one and make sure the bobbin case snaps into place. Something about that bobbin is bothering me, but I can't put my finger on it. Does it sit flush in the case when it's installed into the bobbin case?
After this, I will wait for your responses and think of where we need to go from here.