I guess this has been covered many many times here..One more time..
Carb needles are set by the manufacturer of the carb when they are assembled..They are all set pretty much the same...There is no way anyone can predict what prop size will be used on an engine, so the carb is probably set on the safe (rich) side...If they weren't made to be adjusted they would have no needles at all, just like the new environmentally friendly weedies..
No needles, you run it like it is, rich or not...
I have converted and am converting a BUNCH of G26 engines...I run each one to check it out...I would not think of sending out an engine that was not test run and set fairly close to where it should be...I run the same 18-6 Mejzlik prop on each one..The normal setting is AROUND 1 1/2 on each, but this is not the perfect setting...I start out with each needle open 2 turns..Peak out the high speed, which is around 8800 rpm with my Abell muffler, than back of a few hundred rpm...then set the idle speed about 2000 rpm and slowly lean out the low needle..the engine will speed up...re set the idle speed needle and lean out some more..When it stops picking up speed the setting is close..Re set the idle speed to about 1800 and open the throttle..If the engine dies it needs more fuel, open the low speed needle about 1/8 and try again..Repeat until the transition is good and the idle is smooth...go back and re check the high speed needle...You should be able to get a good idle at 16-1800 rpm with good transition...If you change prop sizes you will have to re set the needles..