401A tension problem in reverse
 

The machine seems to sew a nice stitch forward but in reverse it has loops on the top? What can I check I am giving this machine to my niece today. Thanks for any help!!

Were you able to figure it out? I'm surprised no one responded before now. Loops on top generally indicate problems with the bottom tension. Is it threaded correctly? Do you have a manual for your machine? You can download a free one at Singerco.com under "Resources".
There's a screw and spring on the side of where you drop the bobbin in to adjust the bottom tension. It works just like the tension on a vertical bobbin case, it's just built in. If you still have trouble after making sure it's threaded correctly and that the tension is adjusted you may need to take the bottom tension apart to clean it. It could have some lint or gunk built up preventing it from working properly.
I hope this helps,
Rodney