We recently took out a loan with both names on the title the money used for the down payment, registration and all other up front cost I paid and he was supposed to re pay his share to me later. We've now broken up he took the motorcycle and isn't making any payment I don't know where he's living or where the bike is. I don't want to Have my credit ruined what can I do

If you are married, you file for divorce and make it part of the settlement agreement.
If not, you are stuck being equally liable, no matter who has the bike.
You can report a theft to the police if you want a record of the attempts you are making to do something, but don't expect them to do anything. Be upfront with all this with the loan company.
You can sue in Small Claims for half the bike (each state has different maximums, however) and hope he can be found. If not, you win by default, but that doesn't get you anything more than a judgment. The Court can't collect the bike or the money.
If this is over 10K, I might consider taking the credit hit. It all depends on your own situation and plans for the future, such as getting a mortgage.

This is what happens when you enter into financial agreements with someone!