runs great till gets warm then back fires then shuts off .. but wait 2 minutes and restarts and runs then repeat...

 

Check the tank vent isn't blocked by unscrewing the cap slightly, you can hear the suck if it is, and change the spark plug, could be that failing.

I had a 660 Grizzly with a similar problem a while back and it turned out to be the "power coil" on the stator failing when hot, everything tested OK but as CDIs are expensive we "chanced" getting a re-winder to test the stator coils and they reported a faulty power coil. They replaced it and sent the stator back to us. Bike ran fine afterwards, but fault can be anything on the ignition, plug, coil, stator coils or CDI failing when hot. After plug, stator warms up fastest though so I suspected it would be that.

 

have you pulled the plug to see how the burn is?