If you put in 2.6L as per handbook then you must assume the oil quantity in the bike is correct.
two possible problem:
you are not checking it correctly or oil is leaking out of or inside the bike (god forbid!)
I check mine after a normal run. Try do yours after 3 mins.
Incidently I remember if the level is to the top of the stick then you should be able to see it though the plug hole (specially the oil foam)