You said that you used the tank that came with the kit. Did you also use the fuel tubing for the pickup tube that came with the kit? If you did, I would change that out with some good quality tubing. I used the kit stuff on one of my first planes and it acted like what your describing. Would run fine for a while, then would start to get air bubbles in the line to the carb and just shut off. One of the guys that I was flying with asked if I used the pickup tubing that came with the kit, and suggested I change it, after changing it, I have had no more problems. Everyone I talked to at the field afterwards said they just throw the stuff that comes with the kits away, as do I now.