My engine did the same thing on my airplane. Flew fine through a gallon. Then it would crank and runn for a few seconds. I changed all of the lines and nothing fixed it. I finally let it run for a few second enough times that it fired and has run fine for the past 2 gallons. You may have a different problem since breking engines in on a test stand does cause more heat buildup. But if you have an hour or so, keep cranking it. If it does run, then good. If not, then you needed to send it back to DA anyway.