Craftsman Lawn Tractor Fuel Prolem

[01xtreme]

My dad's lawn mower has started running really weird, and naturally I move back home, and automatically Im in charge of fixing it. It starts and runs fine for about 10 minutes, then it will start to sputter, and eventually stall. Once it stalls it's nearly impossible to start again. I pulled off all the engine covers, and started the engine. Once it starts to sputter, I put my hand over the intake to limit the air coming it, and flood more fuel in to it, and it will start to run fine again for another few minutes, then repeat the whole process all over again. I pulled off the fuel lines, and they all flow perfectly, so the gas is getting to the carb. I checked the float at the bottom of the carb and it's working fine, all the fuel passages seem to be clear and flowing fine. What could the problem be? I've never seen a carb like this before, so I dont know how to adjust the mix ratio. Any help or experience you guys can provide would me very appreciated. I will try to get some pics of the carb, Im going to pull it off again, and check it over once more before we call the sears repair guy and spend money we shouldn't.