Hi Bethers - How long have you had your hamster before you cleaned out the cage? Did you rearrange anything?
Bar biting can be a reaction to changes or stress. Here is a link to some very good advice written by Vectis and you'll be able to get some ideas to try:-
Managing Bar Chewing by Vectis
If you did change the layout in the cage, you might want to put things back as they were before the clean out as that might help.