Craftsman DYT4000 mower with Briggs & Stratton 18.5hp OHV Intek engine started putting out some black smoke when starting last week. Today it started fine, put out a puff of black smoke, and seemed to run fine until I started to mow. It died as though it was fuel starved. Restarts easily but will only run at full choke. Runs smoothly though. When I try to take it off full choke it dies. Has reduced power -- if I try to mow, it will go a little way and then try to die. If I'm fast, and push in clutch/brake or turn off blades it will continue to run.

Mower is about 3 years old with 75hrs. Scheduled maint was done at 50 hrs at the start of this season. At start of season, had trouble starting, was diagnosed as water in gas. In the process of recovering from this, put in new filter and fuel pump.

Last year it purred like a kitten, this year it has always seemed a little rough but nothing I can identify or describe.

Where is the smoke coming from? Why must it be choked to run? How do I fix it?
Thanks

Did you take the bowl off the bottom of the carb? If you had water in the gas and this sat over the season you will have a bit of rust, take off the bowl and clean it, you will see the needle valve and float, make sure they are moveing freely just by lifting it up and down with your finger.Wont hurt to fun a bit of carb cleaner therw the gas after this is done. :)

What year is that Craftman, newer models do not have carb bowls. I would drain the fuel and start with known fresh gas. Add the recommended amount of Sea Foam, or any other good carb cleaner, and then run the engine for a hour or two to see if the carbs cleans up without disassembly. The carb is rebuildable or can be totally replaced for about $195