Small Engines (Lawn Mowers, etc.): Engine sputters and shuts down, briggs stratton engine, preventing vapor lock

Question
Re: Briggs & Stratton engine 14.5 Overhead Valve, Model 287707, Type 1259-E1, Code 020319ZE.  In Poulan Riding Mower.  Problem:  Running great until yesterday.  When I start it and engage mower deck, runs great for a few minutes, then begins sputtering and dies.  (As if vapor locking.)  Immediately disengage mower deck, and within a few seconds engine will immediately start and run great.  Re-engage mower deck, sputters and dies.  When running and restarting, runs great with no engine miss.  My attempted solutions:  1) changed fuel filter, checked lines and gas tank to assure no blockages.  2) Changed spark plug.  3)  Thoroughly cleaned engine to assure no overheating from debris.

If this makes a difference, we've had unusually hot days here (in Arkansas.)

Any suggestions?

Thanks.  -Mark

Answer
I think your on the right track with the things you have tried already, but I would go one step further... Drain your fuel tank and replace with fresh fuel from the gas pump, not your gas can you have in your garage.  It sounds like you have water in your gas.  also loosen the bowl nut on the bottom of your carb to let that drain out as well

If thats not it, there are two other things I would suggest:

1 after you drain your fuel tank and fill with fresh fuel, get some premium gas with a higher octane rating.  higher octane means higher boiling point thus preventing vapor lock.  When i worked for a large engine manufacturer, we would often go to the airport and buy 110 octane av gas.  (this was pre 9-11 time.  Go to the airport now with a 5 gallon gas can to buy airplane gas, be prepared to do lots of explaining!)

2  The only other option is a malfunction ignition coil, although I don't think that is the problem.