I'm looking at my 301 at the moment, and I'm just not seeing what Jim described.
Turn the machine so you can see the back of the machine. Now look directly behind the take up lever and you will see a set screw. Loosen it and with your finger move the take up lever connection to the right and then tighten the screw.
It's me, I know it, because I'm having a highly non-technically minded day. I just don't see the set screw for some reason.
Assuming that the machine is well oiled and greased, the one thing I've found with the 301 is that it's not got the strongest motor. If your tension is too tight, it will labor quickly, long before say a 401 would with the same "tight" tension. The upper motor bearing being somewhat seized will also affect its piercing power, but the tension is really easy to check before you take it to the Singer lady. There's not a lot on this machine that you can't fix yourself (Assuming no bent or broken parts)
Make sure that the tensioner is set correctly - try this post:
http://www.archaicarcane.com/fragile...-equal-stress/
One of my 301s was set really wrong (way too tight) and it howled if I tried to sew with it without helping it get started. I set the tension correctly, and it's much easier to get along with. If it's making a good stitch with the upper tension dial at a "normal" number but the test above shows you that it's way too tight, then there's a chance that the bobbin tension is also too tight, hence "balancing" the stitch.
Does the thread get caught with the bobbin case in? What if you hold the thread tails? If it's just with the case out, it's normal. Per your question on the SSS list: I don't think it's a lemon, I think it's been in need of some proper attention for a bit, and possibly someone was tinkering where they shouldn't have been before you got it.
I would still step through the service manual, I think it would do both of you a lot of good. You'd know that the machine was ready to sew, and it would have less to complain about
