Mower quits, will run with choke closed

I have a Simplicity Broadmoor with a 16hp B&S engine (model 303777). Once in a while I'll be out cutting and the engine will die. It happened over the weekend (only the 2nd cutting this year). If I close the choke it will start up again, no problem, but as soon as I start to open the choke again it will quit. If I let it sit for an hour or two it seems to start right back up and I can open the choke and mow normally.



I've done an ok job of maintenance. I change the oil and filter, fuel filter, plugs, and air filter every spring. I haven't always done the best job of draining all of the gas at the end of the season or getting stabilizer in it right away. Any suggestions? I really appreciate any help.



Thanks,

Nick