Yes, the tank fits fine. I have a K2 tank on my K8. The problems you run into are the seat and the fuel valve. The seat won't match up to the tank the way the stock K8 seat and tank fit, and the older seats can't be mounted to the K8 frame. Also the fuel valve may be in a different place (right side vs. left side) and it might have two fuel outlets vs. only one outlet on your carbs.