I have the answer!! When I took my tank off for paint, I was sanding it and herd something ratteling around inside, I tired to get it out to no avail. Well I pulled the fuel selector out and it was missing the Level tube, or what ever you wish to call it. Basicly it sticks up from the bottom of the tank to run outa fuel before you really are (obvious) well any rate, it just fell off... and was ratteling around the inside of the tank. Im gunna take a wild guess yours did to, and it doesnt matter if you have it on norm or reserve it just runs out. Simple answer! Just get a new one.