How much is my dirt bike worth?

hi i have a 1980 honda xr80 dirtbike and i am wondering how much i could sell it for. the back fender is missing and nothing else. it starts 2nd kick every time. it is a 4 stroke and has half tread left on the rear and brand new on the front tire. i dont know if it matters but i live in saskatoon, saskatchewan canada. any info would help. it would help if you could say how much you would pay and such. thanks alot