Mydragonfly has just developed a sputtering at near full throttle which sounds like the main motor is intermittently cutting out .This is very disconcerting when more than a foot or so off the ground.
Is this the sign of a motor on the way out. I probably have no more than about 1 hour of run time on it and about a half hour breakin at 3 volts. Battery is fully charged.

Any ideas?

It could be the motor or it could be the pinion is slipping. What pinion are you using?
It could also be a bad connection.
What electronic setup are you using? Stock?