> I have checked for cleft palate and can see no sign of it.
If there's no visible sign of cleft palate, then maybe he is just not coping with the flow of milk at the moment. Often this will improve as they mature.
Or he might have a very small hole in which case it may well close up as he grows.
If he continues to grow OK then just keep an eye on him and wipe his milky face as necessary. If you're really worried then get your vet to have a good look with their bright light and special glasses.