My engine was a little tempermental to break in too, but once you break it in, it starts just about every time on the first try. Hang in there, you'll get there.
My problem was that the idle speed was set too low. You have to adjust the carb so it is open 1mm and then dial in the throttle trim on the radio. When you get the engine running, it's going to want to run away on you. I put it in front ofa wall and left it run for a tank after I adjusted the idle speed so it wasn't wearing on the clutch. After each tank you have to make minor adjustments. In the process you have to set the idle speed so the engine will still run when you brake but not run fast enough that it wears down the clutch.
Here are some guides that helped me along the way.
BTW, get the electric starter, it is a lot easier to start. You can get just the starter panel and the drill wand and use a drill to start it if you don't want to buy the whole kit.