[beachbum]

I was having a fuel flow problem on my 150cc at long durations of high speeds, but I haven't heard of this happening to a 50cc. It does seem like that is what your dealing with. You can try what Qwertydude suggested or get a high flow fuel pump.

Just curious, did you perhaps overfill your tank just before this happened? Sometimes if the fuel tank vent gets filled with gas you'll run into the same problem.