Using Zenoah oil with 93 oct. runs ok.

Not sure what the max rpm is.

Screws set right at stock recommend

It's got about 2 gallons through it.

16x6 prop.

No offense but______Stock recommend means exactly nothing, just set to get the engine running...Do a search on setting carb needles...Been saying this for at least 15 years, maybe day it might sink in...
You are the only one that can properly set your carb...different prop sizes, altitude, fuel mixture all have an effect...

When running a richer mix you will get some black oil.. Run in slowly.. It will pay off in the long run..
But do tune yourself once it's running..

I use zenoah or evolution oil ( the blue stuf ) and have very little oil residue. As BigK said if you are running it at rich oil like 25:1 it will spit out a lot of oil. You do also have to tune your engine as Antique said. You want it to run just a hair richer than its max lean setting. You will find that the zenoah oil will not build up carbon deposit like lawnboy and many other mineral and other synthetic oils. I believe that on the bottle it says to run at 32:1 or 40:1, you should probably run it at 32:1 if you use this synthetic oil for breakin. It will probably take a long time to break this engine in. I have never had a G-23 or 26 but I know that a G-62 just gets better with age and that is pretty much the consensus across the board. You should invest in a suitable tach it is kind of a neccesity for gassers.

I have tuned the needles ________. No change. Running at 40:1 currently. Did notice the spark plug was black with some build up. Not the brown that is ideal for 2s Can zenoah oil go bad? I ran a little Stihl premium in it at 50:1. Still spitting black, but spark plug color much better.

I run 3oz Amsoil to 1 gallon premium (43:1) in both my DLE 55 and my Zenoah G26ei. Both engines have more than 4 gallons through them. I broke in both of them with 2 gallons of 30:1 dino oil. My DLE 55 burns the 43:1 Amsoil great with only a small amount of oil spatter however the G26 spatters a lot of oil. I would like to see less oil coming out ot the G26 and am would like recommendations on what mixure to change to. Thanks.

I don't know if zenoah oil can go bad but I had a bottle once that turned completely clear but it was blue. Black is not an indicator of oil burned oil is white so black soot can build up from the gas. I run my engines just rich of max lean and the plug is always a little black. I never had experience with a g23 or 26 but I would think that if you were looking for a perfect rust colored plug it would be too lean.

Tune it and run it. After 4 or 5 gallons of fuel it'll clean up. That is assuming that the engine is brand new and not run in yet. It will just get better with time.