Did you buy the bike new? These bikes are often improved by previous owners with stage 1 jet kits that have titanium adjustable needles, that will wear out you´r needle jets in as little as 5000 miles. Take a look at you´r fuel mixture screws. If they have a brass plug over them they have probably not been messed with. If you can see the screw, chances are that someone has previously installed a jet kit.