I have a Cub Cadet LT1024 with a 24 hp briggs and stratton motor model 446777-0302/E1. I have rebuilt the carb and now it runs really rough and blows out black smoke. If i hold the trottle a fration of an inch open (at the carb) it will finally even out and run smooth, but if i crank the throttle handel all the way open it goes back to running rough again. I have changed and replaced everything that i can think of and nothing seems to help.