My first bike was a '78 Yamaha DT175. Fun but slow 70 MPH was top end.
I have a CB400F cafe'd out, and it is about the most fun you can have with your clothes on. You would think a bike that will only do 80 would suck, but that is not the case. It is impossible not to ride at its limits. I have been cordially invited never to ride it on base ever again.