Im a member of another yorkie forum and I know a woman whos yorkie male didnt stop hiking even after we was fixed.Infact,he was getting so bad that recently she had to find him another home.
His new owner is also a memebr of the same board and she is now having the same problem...so fixing doesnt always solve the problem.I hope in your case that it does help..if not,you may have to get a supply of beely bands