Are you gaining any information about where you are at by checking? Why wouldnt you bet AK here flopping top 2 pair on a well cordinated board isnt exactly a monster flop for you. Sure you are probably 95% to have the best hand but I wouldnt dare give a free card with 2 pair or any ace here and im certianly not giving it with my underpair. If he has the guts to move over me when I raised preflop on this board he can have the pot he deserves it.