hmmm... Check your diff internals, maybe something binding... Check for airleaks ,,, do you get dust build up around the base of your carb ? if so re seal it with some silicone, must be heat and fuel resistant.. Check the seal on your fuel tank,

Engines run at different temps all the time, it could be high temp , for a moment...

If its full speed you may be over leaning the engine ... sometimes engines will starve for fuel at WOT .. ive had that problem before. give it 1/8 turn rich, warm it up and see if it still happens..