If it sounds like a thrashing machine, it's crying for oil. I just tore my 301 down last night and oiled everything I could. It's only been two projects since I last did it.
The problems you are describing are tension related. Make sure there's no lint in the bobbin area and clean out the tension disks on the top with dental floss, then adjust the tensions slightly. If the top thread is the one that pulls out easily, then it is too tight and the bottom too loose. If the bobbin thread pulls out, then the top is too loose.