It originally had some sort of screen. I have found that they are very fragile so if you try to clean one, you'll be jury rigging a replacement. On my 109 SW the original one is a very nice, long tapered piece of ultra fine mesh soldered to the tube. I've always wondered how a big chain saw fuel filter might work on a section of hose so it could roll to the lowest point in the tank when you are running out of fuel on a hill.
The three dimentional mesh screen stops little crud getting in the pump but it ALSO stops big pieces of crud stopping the end of the pickup tube like a strawberry does to a straw in a milkshake. If a big flat chunk wants to get sucked in, the fuel simply goes around to a differnt part of the screen.
