Clogged air filter? that's HUGE machine compared to what I normally work on. Fixed a friends Kioti 55hp tractor... it was working, but man was it smoking black like that. I shut it off, and took the air filter out - literally caked in mud! no idea how it ran. cleaned it up well, put it back in place, and the tractor was running correctly again.
Hope it's something simple for you too!