1991 LT4WD Quadrunner gas in oil

[rangerguy]

Hi all. Having a weird thing go on here. I'm filling up the oil pan with gas. I'm guessing its flowing through the carb somehow. I have rebuilt the carb, three times, used new kit. It runs fine on start up, then becomes increasingly difficult to start once it dies - have to give full throttle until it clears itself. And then, I remove the oil fill plug and its full of gas/oil mix.

Any ideas what's going on? Carb cleaned up nice, new parts in it from kit.
What, is it dumping down the intake and through the valves or something???

By the way, I have two of these quads and I swaped the carbs and the same thing happens to the other quad.

Thanks for any ideas. I'm almost to the point I will have to take it to a dealer - dreaded idea.