I was asked to look at a lawn mower for a friend because he couldn't figure it out. I have since pulled the carb bowl off, it is the carb with the plastic bow and plastic jet. The mower starts up quick BUT it chugs, pops, snorts and bangs as soon as it starts. However if you back the throttle way down it smooths out, and if you slowly lift the throttle lever it will go full speed, but if you just pull it up it starts the same thing, blowing black smoke chugging and has no power. When you do get it full speed, you can slowly engage the pto until a certain point where it will start acting up again. To me the black smoke is meaning way too much fuel, but I dont know how it would be getting so much. When it is chugging, it spits gas out of the intake side of the carb. Any help would be great, I'm stumped on it, I have looked at a picture series of the carb being broken down and mine is missing a spring at the bottom of the main plastic jet.. could that do it? Thanks in advance!