I was in belfast as a kid. I haven't taken route one north in a long time though...I think it picks up on the north side heading north out of portland.
We did go south on route one all the way to new hampshire on the kymco's. Portland to Portsmouth, it was a great ride and almost nobody gave us trouble by driving poorly.
It would be nice riding and great views...taking route one north, but I think it would be smaller than southbound, maybe only two lanes without much shoulder. (never done it though, not sure..)
I actually live on a street connecting to route 1. Our neighborhood, the only access is route 1, main street, south portland. Before we got our house our apartment was located right on route 1.
I often thought about going "as far south" as I could make it using only Route One. I just might make that trip on a small bike someday