Go look at Tammi's blog and watch her video.
https://www.youtube.com/watch?v=kzFX...AyBQ2l-Mzkw7ew she has some good info on that type tension. Clean the center pin and post hole...
I wish a tension was all that is wrong with my 301. I have one with a frozen needle bar. Everything else at least rocks - top and bottom. It is in time out and soaking... That bad boy better work - no bobbin case in it... I think I might have enough parts to build one though. I already rebuilt the tension while it is in time out... it might some day sew.