This was explained long ago, and I'll reiterate what I remember, because I went through it, myself.
Running full synthetic oil doesn't *cause* leaks, it exposes them. The oil will more readily dissolve gunk, grime, and sludge left behind by the conventionals. If you replace all of your gaskets (side covers, o-rings, etc), then replace your conventional oil with synthetic, there should be no leak. If there is, you have a messed up mating surface, or you damaged the gasket during installation, don't have the bolts torqued evenly / appropriately, etc.
However, if you just change the oil from conventional -> synthetic on a 15 year old bike without doing anything else, you may find yourself leak-hunting. I did this on my 97, the first change I did when I bought the bike was to a full synthetic, and the leak chase started about 500 miles later. At this point, I've replaced all the old dried up gaskets and o-rings, and am not dealing with leaks, even though I continue to run the same synthetic oil.
Enjoy, and don't be discouraged: its good oil, but you may pay a small price in gasket maintenance over time. You probably should do that, anyway