I am in the middle or near the end of my bankruptcy and the trustee has said they were not interested in the 4 wheeler and I have 6 months to pay back he 1900 dollar value of the vehicle is that legal ?

No, that isn't correct. The Trustee should have allotted money to approach the leinholder with so many cents on the dollar to pay the loan back. The leinholder has not accepted the offer, and they can do that.

There has to be money left over from this, and that is the amount that they should have accepted.

The trustee has not done his job; is it a court approved bankruptcy?

This is not correct, your attorney should discuss pay off at and make a pan. Or have it sold off perhaps