Like the above posts point out, it's either a tank plumbing problem, a wrong choice of glow plug, bad fuel, or improper needle valve settings. ALL modern glow engines can be flown reliably from the very first tank of fuel.

It's an old wive's tale in this hobby that engines require extensive break-in before you can get a reliable idle or a good running engine. Best break-in is in the air with a slightly rich setting. Ringed engines can run richer, but ABC motors are always run 2-cycling.