Why is gas in the oil on a 2001 big bear ATV?

I ASSUME YOUR ATV IS CARBURETED. CHECK FLOAT NEEDLE AND SEAT. POSSIBLE DEBRIS NOT ALLOWING VALVE TO SEAT, OVER FLOWING CARB BOWL. WORN NEEDLE.DOES FUEL TANK HAVE A MANUAL SHUT OFF VALVE OR VACUUM OPERATED PETCOCK. IF MANUAL PETCOCK IS LEFT ON ALL THE TIME CARB CAN OVERFILL , EVEN WITH A WORKING FLOAT NEEDLE ASSY. IF VACUUM OPERATED PETCOCK POSS DIAPHRAGM SHUTOFF VALVE STICKING. DIASSEMBLE CARB AND CLEAN,CHECK FLOAT LEVEL.