Husky rider w/20hp Kohler Magnum (1995ish). Spec #57528.

For a long time it ran rough. Surges a lot. Throttles up slowly. Blows
black smoke when throttling up. I'm told this is carb problem.

The other day I'm mowing and its running rough and surging. When the
rpm's are on the way up it blows black smoke. But after a while it
starts to stall out. I shut off mowers and it gradually gains rpm's.
Mowers on...dies. Mowers off...slow recovery. I drove back to the
house and it died. Wouldn't restart.

Checked spark. None sometimes or very weak. Found that the spark plug
wire connector is rusted and starting to crumble. Ah hah! Could the
slow deterioration of the connection cause a bad spark which caused
the rough running and black smoking? Soooo, I replaced spark plug
ends. It started up. Ran rough. Sooo, I took the carb off and tore it
apart and soaked it in cleaner. Reassembled. Started immediatelly.
Still gains rpm's slowly. Turned mowers on. Engine immediately dies
just like if the key is turned off. Turn the mowers off and engine
gains back it rpm's.

Any ideas? I'm stumped.