ORIGINAL: oldtyme
OOPS..............forgot to mention that the 15% nitro (Powermaster) fuel that I use has
18% lubricant
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If your engine isn't broken-in yet, you will be running both needles a little fat, leading to the rich midrange. Just don't expect this engine to be super crisp going through the midrange. When the engines were designed, most people flew using the throttle like a toggle switch for idle and full throttle. So it didn't really matter much if the midrange was rich, as long as the engine succeeded in throttle-up.
I've never flown glow engines with R/C throttles at much higher than sea level, so compensating for altitude by adding nitro is an unknown for me. The locals should know.
Ed Cregger