kz305 won't rev past 7k!

So I was riding home last week from work and had to make a hard brake just before I got to my house and immediately my 81 kz305 began running strange. It was barely stumbling along for the last few hundred feet to my driveway and when I pulled up I noticed that I was leaking fuel from my left float bowl. The next day I evaluated the situation and found that it was leaking through the overflow pipe because there was too much fuel in the floats. So I readjusted the float levels to the level specified in my shop manual and no more leaky fuel (which is strange that I had to do because I already fixed them not too long ago), but now the bike will only rev to about 6-7k and when it hits it the bike will slowly decel and pop like it's running too rich. The plugs are also stained black and there's a terrible white smoke coming from the right exhaust pipe.
Since then I've changed the plugs, played with the float levels, cleaned the carbs, adjusted the pilot screws, and gone over the entire electrical system and I still can't figure out the problem. Any thoughts guys?
Thanks!