My personal feelings with synthetic are they keep their viscosity for a longer time so they are a superior lubricant, but with our wet clutch you have to make sure there are no friction modifiers in them. Although this is not your case, with new engines initial wear is important so that all parts wear into each other for better fit. Because of this I myself do not like using synthetic until a motor has at least 10,000 miles or more, however I will use a blended synthetic for longevity of the oil.
There are a couple of motorcycle specific synthetics out there but they tend to be a little pricy. I do like the Rotella synthetic 15W45 myself...