Hey, i am having the almost the same problem with my old childhood toy 2000 DS80. This is not funny, i was just going to post this problem. Well, my problem is that it is running way too rich. Like crazy rich. I had to take off the air filter box cover in order to make it drive a lot better. It is still running like crap, but much much better. That leaned it out. I don't know why i have to do that. There must be a problem somewhere. I cleaned the carb and jets like 10 times, and cleaned every up like the air filter. Everything is stock on bike including jetting. I might be considering a rebuild. If there is anyone to help me with this problem, i would greatly appreciate it.
As for your problem, when was the last time you driven it. Like for me, i stored it for like a year. Then, i started it up a year later and all these problems happened. So i cleaned the carb and everything good. But every since after i stored it has been running like garbage. Remember make sure to have fresh fuel, good spark plug, and a clean air filter. As for the float, you have to like bend the tap on the float to adjust it. It is different than most dirt bike carbs.