Good advice from Schwartzie! Check wheel size first. Syrians usually need an 11" or 12" wheel and dwarfs an 8" or it can be uncomfortable for them to run and can lead to serious back problems. The wheel should also have a solid base (no mesh, sore on feet) and turn freely.
Bar biting is usually boredom. Too-small cages is the number one culprit but you can also give them a bit more to do by giving them as much substrate/ bedding as you can fit into their cage. Even wired cages you can block off the gaps in the bars with a bit of cardboard and fill it right up so they can burrow into it.
Scatter feeding and using food puzzles is also a good way to keep them occupied but cage size is the number one, primo factor usually.
Agreed you should check out the pinned cages thread in Housing sub forum but if you post a pic of yours here we can give you some advice on making it a bit more stimulating
