I have B&S 3hp gas motor that has a dirty carb. The carb sits on top of the gas tank There is a pipe that sits in the gas tank with a screen on the bottom of it that acts like a filter that draws the gas up into the the carb. In the past I have tried to take the pipe off without any success. I don't like putting a hole in the screen, but I need to make sure that the opening into the throat of the carb is clean. Any suggestion. Thanks

Some of these pickup tubes are 6-sided on the bottom like you could put a socket on it and unscrew it. I've never had a need to remove them. If carb is exceptionally dirty I soak it in carb bath for 1/2-1 hr, then thoroughly blow out with compressed air, or, sometimes can just blow out pickup tube with carb spray can nozzle both from bottom and from top in carb throat. If screen filter is clean after this, it should be ok.
thanks,

You can clean the screen by spraying carb & choke cleaner with the straw through one of the fuel pump diaphragm holes once the diaphragm is removed. Follow with compressed air if available.

BTW, The fuel pump pulls the fuel up toward the carb through this pipe then delivers it into a little cup in the top of the fuel tank. It is from there that the carb pulls the fuel in through the main jet in the center that is submerged in this cup of fuel, Make sure this main jet is open as well.