Sounds to me like he is running it too lean and it is getting too hot. That will make it do what you are saying. Richen it up a bit, and try it again. My webra engines need more break in than any other I have run, but I wouldn't take it out. Just richen both needles a tad, and if need be, tie the heli down and get it set right before you fly it. Have done that with many of them to get them set up right.