fire the bike up and grab a can of carb clean... spray around the carb boots, the base gaskets and the crank seal behind the stator..... if there is an air leak you will hear the engine change tones.
I f I had to guess, it sounds like the crank seal behind the fly wheel was damaged when you advanced the timing..... did you have to heat the flywheel up to get it off? did you use the correct puller to remove the flywheel?