i tried cleaning the carb and made sure the jets were clear, ive adjusted the air screw several times and it does nothing. the only way the bike stays running is if i have the throttle wide open and then it still barley runs. it is blowwing solid white smoke out the exhaust constantly and 10 minutes prior it was running like a champ. the oil level was pretty low but i put more in and it effected nothing. please help!