Is the choke working? (visual check)
If so is there fuel getting to the carb?
If so I would say to pull the carb off, give it a real good inspection(easy to do on that bike) and clean her out real good.
Get a nice clean surface a couple cans of carb cleaner some compressed air is nice to blow parts off as you take it apart.
I had mine off my big bear several times and they are a breeze to take apart and clean.
Me:'07 Grizzly Camo edition
Warn 2500lb winch
powermadd handguards
Yamaha rear hard box
SS108 ITP polished wheels wrapped in ITP 25" terracross tires
Stadium Shocks w/rezzy all 4 corners
Power Commander Unit
Airbox kit
EPI sport utility clutch kit
2R racing exhaust tip
2R racing foot pegs and siderails
heated grips and heated thumb throttle
My boys: '05 TRX300ex, '05 Robbs racing TRX115, '03 TTR-125, '06 DRZ-125