Choke sticking? Something is making it dump to much fuel into the cylinder. You might want to just replace the entire carb. After you do that make sure you change the oil and spark plug. Posted via Mobile Device
Pull your carb off.
Reattache your fuel line.
Open the fuel line shut off.
If fuel starts running out of the carb your float is staying open.
If you have a fuel solenoid it may be stuck open. Remove it from the bottom of the fuel bowl (1/2" wrench). Run a jumper wire from the hot side and the other to ground. If it doesn't pull in, it is bad.
I have had this and soaked them in brake cleaner. Dug around with a strand of wire. Blew it out with air and all was well. Just be careful, don't let the brake cleaner stay on any seals for too long. It can and will eat them up.
That is usually what I find wrong with the ones at work. 9 times out of 10 the fuel shutoff was left open and gravity took over.