If I purchased a bike used first thing to do is a compression check and lead down test. If your intake manifolds have air leaks your going to be chasing jetting problems with larger jets. 1211, hondabond, or Yama bond on the intake gaskets seals them up nicely. The single carb requires a much smaller pilot and needle taper is critical. Your main will depend on porting. Could be anywhere from 165 to 205 depending on what's done or not done to cylinders.