RE: Zenoah G62 with a 24 " prop???
Just as a tuning tip.....beginning with pretty much rich needle settings.
Tweak the high needle for maximum RPM.
Then, go back and lean out the low needle until you begin to lose the quick transition from low rpm to high rpm....that loss of transition indicates that your low needle is just a bit too lean....go back and open it up a bit more. I generally make 1/4 turn adjustments on the high needle and 1/8 turn on the low needle. It may take longer to tune, but that way I dont miss the sweet spot.
The needles may interact a bit so after you have sorted it all out this way, you may want to go through the process again...rechecking the high, and then the low...especially if the needle changes were substantial.
It is a pain if the needles are facing the prop. I dont generally like to tweak a needle that close to the prop when it is running...however, I have done it...from behind of course, and only when there is no cowl and very good access and room for a relatively secure body position.
Be very careful, and best of luck.
jim