gas/carb problem with 97 Suzuki King Quad 300?

My KQ starts and runs fine until full throttle when it starts pop and spitting and soon cuts off. I can sit a few minutes, it will crank and run fine again until full throttle and under strain like going up a steap hill. Any ideas? There are no leaks, can't see cracks in the lines, have good high grade gas and changed gas, I've run clean (seafoam) and air filter and plugs are clean and good.