ORIGINAL: Not24
If you really want the engine to run well on 5% nitro, then I would say a carburetor change is in order. You need a smaller intake to keep the need for too much fuel down. When you load the engine up with enough 5% to get it to balance the amount of air it gets, it's just too much fuel for it to burn. It's like putting a cam in an engine that doesn't have the right heads and exhaust system to match it. Power actually improves with the smaller carb because you can get a better needle setting, and fuel draw is also improved. I think Mr Cregger will agree with me on this one.
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Yep, I sure do - to a point.
However, it doesn't have much to do with the nitro, or this engine specifically. I'm of the opinion that any engine that NEEDS muffler pressure to run the best that it can with the carb it comes with, actually has too large of a carburetor and would benefit from a better carb installation.
Super Tigre and other brands used to run smaller carbs, i.e., less air flow capability, many years ago without truly needing muffler pressure due to their "smaller" carbs. Fuel suction was much better and the engines were much easier to "needle".
With all of that said, for non 3D usage and with a fuel tank that is appropriately centered in relation to the carb spraybar, most of today's carbs are servicable. This does not mean that the owner/operator will have the cleanest transition from low to high throttle, but it will be flyable in the basest sense.
Ed Cregger