How did you clean the carbs without cleaning that filter? The internal carb filters are behind the fuel pump. Have to take carb(s) off to open it up. Its about 1/2" in diameter. Look at the service manual blow up of the carb. I remove it with a pair of long nose pliers and clean with carb cleaner.
Do you have the old grey fuel lines. If so they need to be replaced, clean out tank, external fuel filter under dash, and fuel RES/ON selector. Do a search for fuel lines and you will find lots of info.