I have been trying to get this zenoah engine tuned so I can have a reliable idle, before I maiden. Not sure how new this engine is, but it looks pretty new. I got it on an CMP Beaver about 10 years ago. I replaced the ignition module with a new Rexcel. Turning a Graupner 16-8 on 91 octane 32 to 1 gas (zenoah oil). It will turn 8000 easy, has reasonably good transition...but it will idle down around 2200to 2400 for about 10 sec then falls off to 1200 or so and dies. Rebuilt carb (twice), set float needle exactly to walbro specs. ( yes, I have the walbro setting gauge).I have tried several methods mentioned here, but to no avail. Started with 2 turns on each needle, with radio, set rpm to 3500, leaned low needle till rpm stopped climbing, brought rpm back to 3500 via radio, and kept doing that until I got no rise in rpm. Then set high needle to max rpm (stopped leaning needle when rpm quit rising). Runs great, except the idle hangs around 2200 for about 10 seconds then it dropped to about 1000 to 1250 for a second or two then dies. If I'm quick with the throttle stick, I can save it. Not sure why. But it should be around 1500 to 1650. If it wasn't broken in would that hinder idle?
also tried the tune high needle first, then the low, but it would not transition, it would just bog down.
Any suggestions?