Small Engines (Lawn Mowers, etc.): rough running mtd, briggs and stratton, needle valve

Question
I have a 13.5 horse MTD with a briggs and stratton engine,, it will sit and idle fine , when i try to throttle up it starts running rough. I have pulled the carb off , disassembled it, reinstalled , the same, new plug by the way, i have pulled flywheel , seems ok, key is not broke.  it will on occasion throttle up and run fine, as soon as i put a load on it , it starts running rough again, it also smokes, very black, it seems to be flooding out, which would tell me its the carb. needle , float,  etc. seems fine, The second i drop the deck to engage the blades it runs rough,, please help if possible,,, thankyou

Answer
Hi Bob
You are correct. Black smoke indicates too much fuel. Try replacing the needle valve and seat and make sure all jets and ports are open. Also check the magnet on the flywheel and both arms on the magneto for rust and trash buildup which can cause a weak spark. Hope this helps.