is this a new plane or did you buy it used?

If i remember correctly you should have one line from the tank going to the mufffler for pressure and another coming from the tank to the engine. I would try a new glowplug and make sure your ignitor is charged. If that does not fix the problem then i would trace the fuel lines and make sure they are not crossed. Like making sure your line with the clunk on it goes to the engine,and the line with the tube bent up in the tank goes to the muffler. once the engine is started the muffler pressure should keep fuel going to the engine. also check and make sure your fuel stopper is not leaking or sucking in air. If the plane was not new check the fuel tank placement it could have been changed from the previous owner, the center of the tank should be inline with the carb on the engine or pretty close to that. hope this helps you out take care mike