Having issues with my neighbors 110cc kid ATV?

I have a couple questions I hope someone can help me out with. My neighbor bought a little 110cc quad for his daughters for Christmas. Christmas morning they had it out and were riding around on it in the snow (which was nothing more than a slight dusting). As the snow started aculating, the quad sat. Finally last week I coaxed him into trying to get it running for his kids. Obviously, it didn't start. (I asked him if he put any Sta-bil in the gas and ran it through the carb, which he hadn't). So the battery was put on the charger and I came back the next day so we could disemble the carb. The float was completely stuck and I freed that up, cleaned it, then put everything back in in reverse order, making sure the float valve moved freely. Then I took apart the pilot jet and main jet, cleaned everything, then reembled. I checked the condition of the throttle slide (everything was in working order. The carb looked perfect! No gunk or crap was left in it anywhere. So back on it went, all the hoses were attached in the same way they came off. We fired it up and the engine lit with a little choke and held its idle pretty well. So of course now we gotta try it out! So the both of us are riding around on this little baby quad trading off every couple minutes running around the yard, up the road, through my yard and whatnot. Here's where it started acting funny. Once the engine started getting hot, it seemed like there was a fuel starvation issue. We would go to punch the throttle, and it would just completely bog out and die, like someone had kinked the fuel line and it wasn't getting enough gas anymore. Mind you, all this started happening about 10 minutes after we had been riding on it. Once it would cool down, we could go back, fire it up, and it would hold its idle and accelerate with either of us on it until the engine started getting hot again, then run rough or cut out completely. My question is: is it possible the carb is going into a vapor-lock kind of situation from the heat of the engine? The carb is directly above the engine because the engine cylinder is laid out in almost a near horizontal way. Both I and my neighbor are stuck at this point. Any help is appreciated.