I have this engine in a Tai-ji 60, obviously running it inverted. I can't get it to run right in the plane. Yes, I have checked the tank pressure, leaks and all the common things that happen to YS engines. Here's the weird part. When I pull the engine out and run it on the bench right side up it runs perfectly. I have 2 YS91FZ they both exhibit the same behavior. Is there some secret to running YS inverted that I don't know about. I really tired of fiddling with it. I just want to fly. The same engine was in a GP Giles 202 running on it's side. Pulled like crazy. Go figure.

TIA, Brian.........