My ex is not on my lease but he is the co-signer.Can I legally kick him out?

Yes. If he is only a co-signer, then his duties would be to pick up the rent if you shouldn't pay it. If his name is not on the actual leasing agreement with the property management company then yes he can be kicked out. I would just double check this with the property management group to CYA. :) Good Luck!!