Hey guys:

I've setup an OS90 in an Xcell 99SE with 8.18 gear ratio and have been breaking the engine in. I'm still working on optimizing the needles, but, I have noticed that the engine will have a tendance to sound like its kicking or not smooth if the mixture is lean.

I originally had the main needle open 2 turns out, but that was too rich and since then I have been leaning it. The other day I tested more power as I lean it more, and found that at 1.25 turn out the engine was still getting stronger the more I closed the needle. I did leave it richer for another 1/2 gallon, but last night I put it back at 1.25 turns out (didnt test any leaner if there was more power, but certainly the rpms were still going up at full power climbouts as I leaned from 1.33 to 1.25 turns or so).

At 1.25 turns out, it seems to kick sometimes in a hover, so I richened the low end. Last night I richened the low end to what seemed to be the max (screw was vertical from original horizontal position) and it still kicked some as I descended from fff back to a hover.

Now I can richen the high end, but, doing so I know will reduce the top end power at full climbouts though it will probably stop the kicking sound in a hover. Its hard to explain the kicking sound, but, if you heard it you will know what I mean. Also, even though it sounds kicky, the tail is still smooth and its unlike what you see in a gasser with the tail wagging with every kick.

Just want to hear your opinions about it if you can help. As an FYI, its running 700mm blades at 180grams each, and the top end pitch is set to 10 degrees at 1700 rpms, 10.5 degrees at 1600 rpms, and 11 degrees at 1500 rpms. With the needle at 1.25 turns out, it can maintain those rpms at full power climbouts, otherwise it starts losing rpms due to richness.

Open to thoughts and ideas guys...!

-=>Raja.