yamaha EF3000iEB

Generator has 28 hrs run time. Engine has started to rev up and fall back all the time while in econ mode. Same thing under load, however not as severe. You can watch the movement on the carb. linkage. Generator is under warranty, however nearest shop is 100 mi away. Tank is clean, fuel is fresh. Saw a blog where another owner, same machine same problem. Is this a common problem with this machine? Need some direction with this if some one can.  thanks B  Note: Machine is brand new and never been abused.