It does sound like he is too lean. He went through 10 plugs inside a week!! That's way too lean or he is running the wrong plug for that motor. Take the whole unit to your local hobby store and let the guys there tune it for you. Once you get an good tune on the motor think of it as a starting point. Everyday and sometimes more than once a day you will have to make small changes to the High Speed Needle to compensate for the relative humidity or outside air temp.

Just stick with it and it will all make sense soon. Your at the right spot for getting information / help in this hobby .
And forget about trying to compare these motors to full size 4 stroke gasoline engines.