You are going to have to take the carb apart and clean it wit compressed air to make sure every fine particle of dirt is out. I worked on one all afternoon tearing it apart 4 times before I got it to work right. As for it accelerating when you close the choke means it is sucking air from somewhere and then stalling out. Make sure you are not missing any parts when you put it back together. Try to get a manual if you can.