I second what Linda said. When I got my Featherweight, it sewed fine, till I cleaned and oiled it. I took off the needle plate and did all the normal cleaning stuff. Put it back together and it was a mess. It is a miracle I did not break something in there.
I looked at the online guides and thought I was putting it back together correctly. But it still would not sew. It was so exasperating. I finally just happened to go to a little quilt shop in Vegas. I noticed they had several FW's there and got to talking to the gal in the store. She showed me exactly how to put the bobbin case back in the machine. A light bulb went off and I knew what I had to do.
So, ok, here is what you do. Take off the needle plate and look at the bottom of it. See the two little box type looking things that are on the bottom? They stick down a bit, maybe a quarter of an inch. Now look at the bobbin thing that comes out when you oil it. Not the bobbin case, but the part the bobbin goes into. I forget what it is called, but it has a pointy part and a boxy part, and is round. When you put this in you need to make sure the little box part on that goes into the space between the two on the needle plate, which would be at the top. It is tricky, but you have to hold this all together, bobbin thingy and needle plate and screw it down. Make sure it stays before you put the bobbin in.
Clear as mud, right? Hopefully this is all that is wrong with the machine.
Mine sews, but I hear a little clink so I plan to take her in and have her looked at. The husband of the owner of the little quilt shop I go to is a Featherweight specialist. So I think I will have him look at it. I have heard other FW's running and they should hum like a sweet child, no clinks, tinks or grumbling. Or so I have been told.