If the needle & seat assemblies on your carbs are working as they should, leaving it in "PRI" wouldn't let gas into the engine. If one or more of them is stuck open, or if a float has sunk (has fuel inside it), fuel could slowly dribble its way into the crankcase. If your oil level has gone up, or it smells like gas when you remove the oil filler cap, you've got gas in the crankcase. If that's the case, change the oil and filter and life will be good - once you fix the float needle & seat or float problem.
More likely problem:
If you let the bike sit for more than a month with fuel in the carbs (and with it left in "PRI" fuel would be in them), you're problem is at a minimum stale gas. The next stage is the gas turning into a varnish like substance that clogs/restricts jets.