ORIGINAL: bigedmustafa
I'd recommend that you read through Frank Granelli's excellent article "Engines 101 - Part Two" about setting up and tuning .40-sized 2-stroke engines at the AMA's Sport Aviator web site:
http://www.masportaviator.com/ah.asp?CatID=8&ID=47
This information should help you check your engine setup and needle settings to help with tuning. Finding a fellow glow flyer who's good with engines would be even better. Good luck and feel free to post any additional questions as they come up.
Wow, nice article, but whoever did the technical review missed a minor slip through that's actually pretty significant. Near the end it says "After about 10 flights for ABC engines, 20 flights for ringed engines, the high-speed mixture can be
leaned to 500 rpm less than peak. Never run leaner than this." The word I maked with bold should be richend, not leaned.
I also wasn't crazy that he covered setting the low speed needle before he ever got around to talking about the high speed needle. Typically, the low speed needle is pretty close to the factory, but if it's not, the high speed needle should always be set before any changes to the low speed settings.
Anyway, here's how I set my high speed needle.
Tuning – High speed needle
The following method is designed for sport flying where one wants reliable engine performance (minimum deadsticks) and long engine life (part of which comes from avoiding lean runs).
I’ll start off with a reminder that all needle adjustments should be done from behind the engine and that the plane should be firmly anchored or held. Never attempt to adjust the needle while holding the plane in the air. A small engine blip or wind gust could result in fingers in the prop.
Begin by gradually leaning the engine until you find the peak RPM. Once you find this, turn it several clicks rich. Once you’ve found this slightly rich setting, with a firm two handed grip on the plane, point the nose straight up. While you are doing this, remember to keep the propeller arc out of anyone’s face. When you raise the plane’s nose, one of three things will happen to the engine RPMs.
If the engine speeds up slightly and holds that speed for 10 to 15 seconds, pat yourself on the back (after you put the plane down), you’ve got the needle set pretty well.
If the engine slows down, or does not speed up a bit, it’s too lean. Lower it immediately, turn it a few clicks richer and try again.
If the engine speeds up significantly, it could probably be a bit leaner. Put it back down, set it a bit richer and try again.
That’s it, no magic…