Carb problem.

I have a TV... (motor with plastic carb). it wont stay running. prime and it starts. I took off the carb and cleaned everything out so that is is spotless. This is the second one that i came across that acted this way. The first one I tried rebuilding with same results so i dont want to buy and get the same result with this one.
Am i missing something?
TIA

Start the engine and see if you can keep it running by continually giving the primer a pump . If so the carb needs cleaning.
DO NOT USE SPRAY ON CARB CLEANER Ultra sound and simple green works well.
Replace the needle & seat

If priming won't keep the engine running try squirting some shots of starter fluid down the carb, If you can keep it running also clean the carb but clens out the fuel tank & fuel lines as well.