How many miles on your bike? Are you using considerable amounts of oil? Valves being out of adjustment shouldn't cause you to burn oil.. Maybe if the exhaust is excessively tight creating more crankcase pressure.
Most likely you just overfilled it with oil. Causing an increase in crankcase pressure, pushing the oil into your airbox.
Otherwise the most common places for oil bypass is valve stem seals (smokes at cold start) Or around the piston ring. Both will get consistently worse over time.
Just check your oil religiously. If your burning a little bit its not the end of the world. A little extra lube wont hurt.