Small Engines (Lawn Mowers, etc.): Engine Wont Stay Running, starter cord, spark test

Question
I nave a new Troybilt 5500 generator and the engine (10hp B&S) runs perfectly for about 30 minutes to several hours then suddenly stops like it runs out of gas.  It starts right back up, usually with one pull of the starter cord, but will stop again after 30 minutes to several hours.  The fuel lines and gas tank are alway full.  We have cleaned the gas tank and added fuel additive but nothing has changed.  

Answer
Well joe it sounds to me like you have one of 2 problems. My first guess would be that you simply have a bad vent in your gas cap. This can be found out by running the generator with the cap loose. If the problem doesn't return, replace your cap. The second guess would be that your ignition coil on the engine is bad. When it stalls out do a spark test, and remember you have to have the plug grounded. Hope this helps you.