RE: Zenoah G62 with a 24
22 x 10 will get you what you want most times.
1and a 1/4 turns on both needles to start and tune from there.
Once transition from idle to full rpm is achieved by tuning the low neddle (L) then focus on the high (H) needle.
I normally use a 30:1 oil mix a little extra never hurts for run in, after that I use 35:1 mineral based until you are happy with run in then go to a synthetic oil.
Remember these are agricultural engines for Chainsaw and Whipper Snipper use and are well suited to have the crap run out of them. Just keep an eye on the temp.
Suggestion here is to run it hard for a good 10 to 15 minutes air time and then rest it allowing to cool down, then go again. I would not worry about bench testing unless you wish to ensure everything runs well before mounting in your aircraft.
A regular check of the built in gauze filter in the carby is well worth doing and a rebuld kit ever few years helps too!
I have found this works well enough for me to use the G62 as an aircraft tug for gliding on a 22 x 10 or for Racing a 32 lbs model Spitfire 96in wingspan on a 19 x 14 prop and win the Adelaide Warbird class in 2003. and still place in 2005 and 2007.
Hope this helps.
Crash Carpenter
Adelaide
Australia