Anyone know what the optimum needle setting is for the OS 55 AX? The manual recommends 2-2.5 turns for starting which is more than what is recommended for the 46AX or 61FX. Thanks.

G'day Mate,
Follow the instructions, that's what they are for, as it runs in, you can lean it out a bit at a time.

Ran the first 2 tanks of fuel through my new 55AX today. The 2 - 2.5 rounds out will work just fine as mine started right up at 2.5 rounds. Was somewhat rich there and very soon I had tweaked it in to 2 rounds. Towards the end of the second tank was just over 1.5 rounds out and it was still rich. It would go lean at a little less than 1 round out.

I think its going to be a nice running and powerful engine.

Hi!
You must listen to the engine and set the high speed needle accordingly!
Knowing the exact turns is just meaningless knowledge (isn't exact enough).
You can hear when the engine reach it's peak rpm???

Yes, I know when an engine is peaking, I use a tachometer for that. However, I thought that this engine would be close to the OS 46FX/AX in terms of needle settings since it is almost the same size. Thats not the case though, the high speed needle on the 46FX is at 3/4 for peak rpm while its probably at 1 1/3 for the 55AX.

I guess this illustrates just how different the 46FX/AX is to the 55AX. The power on 55AX is amazing.

Every engine is slightly different, even when they are of the same manufacturer and model. Even your engine is slightly different from the last time that you tuned it due to wear. Engines change a bit throughout their life time.

There is no way that anyone can recommend an optimum needle setting for you. Get that type of thinking out of your head. It is guaranteed to fry an engine.

Check the needle setting on the first flight of every flying session, whether two-stroke or four-stroke. That means turn the needle valve and find the best setting for that day and then add some clicks toward the rich side. You will find that in a short period of time, you will have learned how to tune your engine. The more you adjust it, the more you will learn. Your mind will memorize things even when you are unsure or shy of turning the needle valve. The only way to learn how to tune an engine is to tune an engine. They aren't that delicate. <G>

Folks that tell you that you don't need to do this do not know what they are doing. I don't mean to be rude or insulting, but it is the truth. Good luck, not that you need it.


Ed Cregger

Nicely put, Ed.


I will add something a bit more categorical...

The right settings for both needles in any engine are the settings that work.
There is no such thing as a "don't touch anything" initial setting and any setting is judged as good, or bad, by the way the engine runs with it.

Any initial setting that allows the engine to keep running, even if it is burping, wheezing and farting, like a mad squirrel with hiccups, is a good place to start, as long as you can determine it is is too rich, or too lean, so corrections can be made accordingly.