Could be too much carb as well.

With a carb thats too large, they will run up to about 1/3 or 1/2 throttle and then die suddenly when you advance throttle. As soon as the high speed starts to kick in and dump fuel it drowns the motor.

This is in extreme cases. But it's just something I learned along the way. Too much carb isn't any better than a stock carb. [8D]