How do I get my motor bike back?

Over this past summer an acquaintance of mine from work offered to work on my bike motor. I had seen some if the work he had done and figured it'd be my cheapest option. I gave him the motor to work on, bought the parts for it and so on and he ended up quitting and getting another job somewhere else and I have not seen nor heard from him since August. I've tried contacting him on numerous accounts to no avail but people I know have contacted him and he gets in touch with them. I was just wondering what my options are here to get my property back.