today i started my bike adn let it run on choke for 5 mins. i get on it adn give it full throthle and it pops off choke like its suposed to and it go about 20 feet then bogs down adn stalls. so i rode it on almost all the way choke but every time i let off the choke it would go for 20 feet and bog then lt would loose power.i ran it for a good 20 mins and still had the same prob. i think the carm might be dirty but it just started doing this. what do you think?