Sorry, I posted this under 2 cycle by mistake.

I have an older Craftsman edger with a 3.0 Tecumseh motor. It starts and runs fine but when you shut it off gas drips out of the air cleaner (about a drop a second until the tank is dry). I replaced the diaphragm and needle and seat and no change. Any ideas????

Did you check to make sure that the float is not leaking? If the float has a hole in it, it will fill up with gas and sink, and let gas go through. You can tell if it has liquid in it by removing it and shaking it. You can hear if there is gas sloshing inside it. Also check for holes or cracks. Submerge it in water and check for bubbles.