I always stuck with cb360's and CL/CB350's. I had a CL175 too. Personally, I wouldn't go less that a 250cc but would try to hover around the 350cc range. Why? You can hit highway speeds. Working on them to me, is much easier. One or two carb issues instead of 4. Lighter bikes too. I have my 79 KZ650 for sale mainly because I want to do another CB350/360 build. I built them to ride them. Not to show them.