Have a craftsman 917.379470 with B&S 6.5 hp motor , with primer bulb. Primes great, can see plenty of fuel when I prime it. Starts on first pull, then dies in about 2 seconds. Cleaned carb in ultrasonic cleaner, fresh gas, new spark plug. Had a new chinese carb I put on and it does the same thing. When I take the carb bowl off, it is full of gas. Looks like it has a new primer bulb also. Any ideas?