We're working on my flying buddy's G26 this afternoon and we have problems getting the correct idle setting. Seems like we are one click to fast and one click too slow. in other words, at the lowest setting the idle is too low, but only one click up results in an idle too high. We can't split the difference. Looking at the amount of servo throw, the difference is in the travel between the two clicks is so minute, it is almost not detectible to the naked eye. Could it be the idle is too lean? It has us stumped! Engine is mounted inverted on a Big Stik 1.20 (no cowl). Runs great at high motor.

Cajuncharley

Hi, My ZDZ 80 on its 1st run up was perfect idle. 2nd days run, It would idle down to approx. 1500, but slowly die out. I had to click it higher to keep it running, then it would be too fast. I then experimented with the low speed needle. I had to lean it out a bit. Now Im getting a consistant idle. I know these are two different types of engines, but could be your low speed is too rich. Not knowing your needle settings, thought Id add my 2 cents. Good luck!

Very probably your idle mixture is out of whack.
If it tends to speed up in rpm and rpm ar not stable, the mixture probably is too lean, but like cajuncharley said, there is a possibility of it being too rich. Adjust and find out which is which.
remark,
changing the idle needle also results in a needed high needle change.