Carbuertor problem

Need some ideas please. Disassembled the carburetor and cleaned, changed needle valve and seat. Sometimes it will start and idle for a while then die. Sometimes runs long enough to go a few hundred feet down the road then will die. It seems as starved for fuel, but then will start again and do the same. Float does not seem to be stuck, because it will start again after it dies. Petcock and tubing is clean as well.