Well,

For me, it's always been more of a 'feel' or 'sound' than a number. The problem is that those engines are so very easy to screw up (with a quickness) if you do it wrong. That's why I was never willing to buy them used (even "bench run only").

I start with 1-3/4 turns out from closed on the high end, and close the low-end needle down 1/4 from the factory setting. The book says the low end is factory tuned, but that's BS. It's way too fat out of the box on a Dynamax.

I prime it and start it at about 1/4 throttle and slowly run it up to full. It should be so fat (rich) that it barely stays running. I pinch the line briefly and it should jump way up in RPMs. I close the high-end needle a couple clicks at a time, pinching it in between to see where in the high-to-low 'spectrum' I am. I keep doing that until the engine is screaming, but still briefly jumps up about 5% in RPMs with a brief pinch. If it holds steady RPMs or bogs down (AT ALL), it's too lean.

Once I have the high-end RPMs at what sound like about 95% of potential, I throttle down and set the low-end. At an idle setting, the engine should only cycle up in RPMs about 15% before quitting with the low-end needle set right. If it dies right away at the pinch, it's too lean. If it runs forever, or cycles up in RPM dramatically, it's probably too fat. Once it sounds right and can run reliably for at least a minute, I test the transition. If the low-end is set up properly, the engine should go from idle to full speed instantly if it hasn't been idling for more than 10 seconds or so. If it's been idling for a while, it may hesitate briefly before going on the pipe. Funny thing is, cutting out when you try to throttle up quickly can be an indication of a too-fat or too-lean low-end setting. You have to play with it.

Once it's sounding right, fly it. It doesn't need to run rich or at idle for a long time like some other types of engines. If you land and the head is significantly discolored, richen it up. Some people will tell you that carmelization is normal or just a matter of what kind of oil is in your fuel, but the most longeve engine I had was on O.S. .91 that ended up with about 300 run cycles on it before it went to the Lord, and it was bright silver. Not black--not brown or whatever. And believe me, it flew those Starfires around such that you couldn't have accused it of being too rich.

Hope this helps.