check out http://wem.walbro.com/walbro/family2.asp , and find out all about your carb.
The inner screen filter is the carbs last defense to hamfisted users. It should be clean. If any dirt ever is found there, the tank setup is to blame.
Common errors:
t-line in carb suction line
no filter in carb suction line

The way to do it:
three line tank. One line for filling up, plugged when not in use.
one clunk line with felt filter clunk or sinered element, going directly to the carb.
One vent line, always open