Personally, I would not sell the YZ either.
I have motocross bikes ranging from 73-77 and I wont sell them, they give you the biggest buzz when you ride them.
I'm still cranky about selling the TY175, in hindsight!!
I have a list of peoples names who say they will buy my 320 when I decide to sell it!!
They will have to talk to my eldest son, I have just started teaching him how to ride it and he loves it so its not going anywhere.