- which you've no doubt seen and know already (so no revelations here).

Yes, three quarters of a turn open sounds like a whole lot, and very rich compared to what you guys are used to running.
But the OS manual has a diagram w/steps (or needle valve positions) numbered 1. thru 7.

It shows a "rich" needle setting for starting the engine at position number 1).
1.)that is almost 360 degrees for open - or a full turn (from the closed position, which is what I called a 3:00 O'clock position).
2.)begin "leaning" with a clockwise turn of the needle to a point that looks like a 75% or 3/4 turn from the closed (or 3:00 O'clock) position at which the
3.) ....the exhaust note changes.
4.)dissconnect glow starter
5.)advance clockwise (until you hear an intermittent 2 stroke note superimposed on low 4 stroke sound at a point that looks like a half turn open at 9:00 o'lock - from the 3:00 O'clock closed position.
6.)clockwise turn from this point gets a clear high pitched 2 stroke exhaust note, with a practical best optimum needle setting w/in a 20 to 45 degree setting around the 12:00 O'clock position


Anything leaner than that last needle setting is called "maximum rpm setting" - or "Lean".

So, I agree w/you, - I'm obviously running a pretty rich needle setting at a 3/4 of a full 360 degree neeedle turn, BUT that's what the manual says to do.

In fact, it says to do the first three or four flights this way at the 3/4 or 75% neeedle setting in number 2.)above....where the sound breaks into 2 stroke from 4 stroke.

I'd like to "lean it up" for more rpm - but it wouldn't stay running after I advanced the throttle past 1/3 power.

I don't think I want to do dead sticks w/ the instructor for the first three or four flights, which (based on my ground tests) is likely to happen if I set the needle any leaner than 3/4.

The manual says after ten to fifteen flights, the engine should run continously at optimum setting w/o loss of power.

I'm concerned that based on what some of you say, the ABC type engines should be "broken in" hotter (leaner) than ring engines - so I'm not sure how long I should be running it rich like this.