Originally Posted by surfer_kris
You might have to much nitro in the fuel, mine does +17000rpm on that prop and 10% nitro. Check the number of shims and optimize for top top revs, staying on the side of slightly too low compression.
Another thing to look for is the throttle barrel, it is important that it lines up with the carburator bore at full throttle. It can be off sideways, as it rotates on it's threads, or it might not open fully if you have the throttle stop screw still installed (just remove it, it is not needed).
A cox babe bee will do more that 12000rpm on a 6x3, there is certainly something seriously wrong...
Take off the engine from the plane and run it in on bench before you put it in a plane.
I can certainly drop down in nitro to see if it makes a difference, but I don't think that's the problem. First reason is that the engine needles beautifully-engines that are high on nitro tend to have a very narrow needle range where they are happy to run at peak power. The second is that Norvels are typically very undercompressed from the factory, or at least the .049 and .061's are so it follows that the .074 is too given the target of being a milder tuned sport motor.
Makes me wish Norvel had made an AME version available.....