New Craftsman 29000 Riding Mower engine question

Sears just delivered my new Craftsman 30 inch riding mower Model 29000. Starts up fine and runs okay. Doesn't stall. However, the engine sound is not steady. Instead it has a rhythmic wah wah wah sound which is constant and at all speeds. Could this be something which fades as the engine breaks in or is this a carburetor/spark plug issue? Thanks for any help. Will call Sears to check it out if I can't find the answer on my own.

Post model number from under seat, thanks. Check engine oil level before every time you mow.