I am having the same problem that all around in this thread. My engine is mounted upside down, I guess that because of the size of the propeller I cannot reach the high pitch sound at high speed as with the .61 or .45, but it has being hard to adjust the low end. I am using 5% nitro gas, and OS A3 plug and an exhaust deflector. Any suggestion to this setting?

Given what I read in the thread, it looks that it would be a good idea to adjust the engine upside first. What I have seen in another model, is that when you turn the model upside-down to have the engine upside, the muffler line is located in the lower part of the tank, and therefore the muffler is flooded. The question is, I can strangle the muffler line to start the engine, but what I have to do after starting? If I keep the line closed there will be no entrance of air and the fuel will not flow for too long. If I release the line will the fuel flow towards the muffler??