Help!

I have a 04crf150f and I have been having a little problem...
I have had the bike for a week now, and everything has been running fine..The other day I took 1 or 2 pretty good spills, however, the bike came out running fine..This morning I went for a ride and I noticed that when I ez off the clutch (i.e., in first gear) and I roll foward, I not only roll foward, but the bike runs as if I am giving the bike gas and revving the throttle (Even though I am not touching anything) On top of that, when I try to give the bike gas, the engine just chops and I don't gain any acceleration whatsoever... I have fiddled with the choke, but see no difference besides the speed (when my hand is off the throttle) I don't have too much experiance with dirt bike maitenance, but I called my dealer and they said that the spark plug tip could be chipped but it was hard to tell and I would have to bring it in next week.
So, sorry if this is hard to follow, but I can't figure it out! If anyone has any solution, or have experianced this problem please post as soon as possible, b/c as of now I can't ride! Thanks for you help, I appreciate it.

I will pick up a new plug and see what happens....About the lean condition, can you please explain yourself a little more thoroughly because I am unfamiliar with the whole "float" and "sticking" deal.. Thanks! Any additional info. is aprreciated.

Also, it has been in the low 30's around where I live and I keep my bike in the garage (low 40's) and for the first week I didn't have any problems, but as of late it has been pretty cold.. Can the temperature have anything to do with this condition?
In addition, I let my brother ride my bike the other day, and APPARENTLY

he messed with the fuel screw or something, could adjusting this have an affect on the condition of the bike? Thanks

I screwed the fuel screw out a turn or so and I noticed a slight improvment in acceleration, but the engine still bogs and throttle dies from almost 1/4 to WOT... But just not as bad... Should I give the screw a few more turns and see what happens?

I was out this morning and after a couple minutes of just cruising around (without throttle input :) ) My pipe started to smoke and everything seemed to be not working correctly.. I am very concerned, but it might just be my plug i dono.

well i dont know if black smoke is what you mean:)