you should not do it... it could kill you... if your a kid and blow up dads new mower, he'll kill you, if your married and blow up a new mower (and void the warranty) your wife will kill you...
seriously though, stare at it, when its running, if you don't get how a carb works then don't mess with it, it really will void your warranty. if you blow it you'll be paying out about half what you paid for the mower just to get the motor (plus installation fees).
(with a formula, thats a fairly new engine according to the guy at my local authorized stealership, cuz I have one too)
have you improved the brakes? steering?
oh yah, and welcome to the forums