Hi!
First of all a 14oz tank is way way to large for a .46 Engine!!
Why!
Because our glow engines cannot cope with the vast difference in fuel pressure that a large tank develops. This is noticed in that the engine runs leaner and leaner the more fuel that is consumed and finnaly the engine stops! A remedy to this is to use a tank that has enough volume and still makes the plane fly at least 10-12minutes.
So in your case a 8-10oz tank is the way to go!

So...if you only can fly for 4-5 minuts ,you either have a leak in your tank/ fuel line or running your engine exstreamly rich.
What prop and rpm are you running?