Small Engines (Lawn Mowers, etc.): MTD/18hp B&S Twin wont keep running, tank fuel, fuel flow

Question
I have a MTD 18HP B&S Twin - riding mower.  The engine will start fine with the choke all the way out.  After warming up for 20min (longest I had it warming) I push the choke in and the engine dies.  Moving the throttle doesn't help at all.  Just dies unless I pull the choke out right away.  Can't mow like this either - once gears (F/R) are engaged, the engine dies.  Replaced battery and plugs to start.  At my wits end here.  Please advise.  

Answer
Hi Roy,

First, check the fuel flow from the fuel tank fuel line at the carb inlet.  If good, the carb most likely has dirt, debris or gummed fuel inside.  You will need to remove the carb, disassemble it, clean all the small internal openings and blow it out with compressed air.   Probe each and every hole with a small wire.   A carb rebuild kit wouldn't hurt either.  

Let me know how you make out.
Michael