you might be running out of fuel, but its not because the carb. bowl ant holding enough fuel, its gonna be because, the floats are to low, the pressure reg. hooked up wrong, fuel pump problem or fuel line sucking togother, but we cant see all of that. you seem to know a lot about those carb. yourself, its only so much we can tell you without looking at it. im not so sure your not floating the valves. can you run it just on the primaries, cut the secondaries off. and see what happens.