G'day Carl and others.

A couple of comments -

Your method of tuning is pretty spot on. If I am tuning an unknown engine, I always start by making sure it is in a rich setting and then work to lean from there. Once you get it to the point where it is on the "two stroke/four stroke" boundary - ie it is missing some of the time, then you are close. With new engines, I usually lean a little more but don't go to the extreme lean limit.

And secondly, as you add nitro, you need to tune richer. Nitro is essentially "liquid supercharging". It adds Oxygen so you can burn more fuel so you need to open the needles. You also use fuel faster which is the down side. The upsides of nitro are broader tuning tolerances and a bit more power. I once tried 100% nitro by accident. It really makes a lot more power but it needs a VERY rich mixture and it threw the blades off the prop. The nylon blades stretched! The engine survived. It is not a recommended way to get more power but it was interesting.

Generally speaking, if the weather is the same, the temperature about the same, the prop the same, the plane the same and the fuel the same, you don't need to tune each flying day. My four strokes go for months on the same tune.

Also remember the old car racer's advice - "cold and wet - bigger jet" or in other words, you need to tune richer if it is cold and leaner if it is hot.

Cheers

Mike in Oz