Quousque

I just picked up a 301 on craigslist. It's in fairly good condition, but hasn't seen maintenance in a while. I oiled it up and gave it a test run. It makes a clicking sound once per stitch. I think it's coming from the bobbin area, but it's hard to tell. When I turn the handwheel, I encounter resistance at a certain point in the turn, right as the thread lever is coming back up. It's easy to push past it, but there is a slight "grinding" feel. The click doesn't happen when I turn the handwheel by hand, so I don't know if the resistance and the click happen at the same time.

The stitch formation is not good, I was getting big clumps of thread on the bottom of the fabric. I don't want to try and fix that by adjusting the tension, since I'm reluctant to sew on it in case the clicking and grinding feel could damage something.

I know I have the correct threading/needle/bobbin etc., since I grew up sewing on 301s and am familiar with how to use it.

Any ideas what's going on? I'd like to try and fix it myself before paying someone else to do it.