It's obviously a fuel delivery problem. The first thing I would check is to make sure that the bowl is full of gas. As soon as the engine dies, turn off the petcock and then open the bowl drain screw - does gas come out? If not, you may have a clogged fuel line or filter or your float level is set too low.
You could also have one of the carb passageways clogged. In order for the bowl to deliver gas thru the jet(s) and in to the Venturi you have to have a flow of outside air into the bowl. If not, the bowl will become a vacuum and stop delivering gas until something fills the space (ie. gas from the fuel tank) and then it lets you restart and it'll run for 15 more seconds.
Hope this helps
Posted on Nov 21, 2005, 8:14 PM from IP address 69.230.185.164