Changing Humanoid Position not working, Why?

Im making my own placement system for a game I am working on. While working on it I realized only the part I was stating to change the position was moving. Yes, they are all welded together as Motor6Ds. Here is my code:

    local X,Y,Z = Mouse.Hit.X,49.233,Mouse.Hit.Z
        Preview.Parent = game.Workspace.Previews
        Preview.HumanoidRootPart.Position = Vector3.new(X,Y,Z)