Not strange, they loosen up slowly until you notice something is different. As the engine breaks in it's also going to want to be leaned out and set in a correct tune. If it's still set fat it's going to be blowing snot out of the carb too and be building up in some odd places.
Saito is a fat running snot blowing pig compared to my other four strokes until I tune it correctly. Even then it blows more crud then the others but it is what it is and it is a pretty good running engine.
There may be nothing loose at all, it could just want to be leaned and is just mentioning it to you in it's own way!! It's just a machine and it's talking to you in it's own language, just up to us to try to understand and listen.
As 8 mentioned, it's getting plenty of oil!!