I have a new engine that only has a few tanks of fuel through it. I've had lots of help from some of the more experienced members of my club in getting it tuned and it seems to run fine while it's running. My problem is that I only get a 6-8 minute flight and then it deadsticks! I pulled the tank out to see if I had a clunk problem and I found that I still had 2/3 tank of fuel left! There is no problem with the clunk.

Engine: GMS .47
Tank: 9 oz (270 cc)
Plane: Avistar 40
Fuel: 15%

Any ideas???