Had a similar problem, engine started new out of box and ran great. Got 2 minutes into maiden flight and it quit dead at 75% throttle flying straight and level. No amount of work could get it to restart on the ground. Checked for spark and found it had none. Tried different plug and ignition, still no spark. Spent a lot of time futzing with batteries, switches, and VR, no luck. Finally just happened to notice that the magnet for the Hall sensor was gone! Never occurred to me to check for that. The engine apparently spat the magnet out and that was all she wrote. I know OP says he has spark, so it can't be this, but point is, sometimes it's something so basic you don't even think to check for it.