I am trying to figure out what is wrong with my little brothers 94 300 bayou, and I'm stumped. It runs fine at idle thru mid throttle, and at mid to full throttle it hits fine a couple of strokes then bogs extremely bad and then runs fine again and bogs again and on and on. I have cleaned the carb, adjusted valves, cleaned the air filter and spark plug, and regapped the plug. Anyone have any ideas of what it could be.

Sounds like the float needs adjusted or the needle valve is sticking.

new fuel filter??

Just giving a shot, myabe try the oil my old bayou 220 you to bogg real bad when it was hurtin for new oil.