MOPED ARMY

I just got a 77 Peugeot 103, It's in great shape. I cleaned the carb , put in a new spark plug, new fuel line. The problem is it doesn't seem to be sucking enough gas. It will start and run for about 3 seconds then die. I took the carb off and cleaned it again, but it still wont stay running. I know there is gas going into the carb, but not enough to keep it running.

any thoughts?

thanks russ