Here is my limited experience with these engines. Mind you I am only a couple years into airplanes but have been flying helicopters and driving nitro trucks for over 5-7 years.

My JBA is a .46. I bought this from a guy at a fun fly. I Put it in my nexstar. I flew three flights with it with no issues and seemed pretty nice. But after that I can not get it to stay running pointed up in the air. It idles..sometimes when I throttle it to the max it stalls and wont run pointed up. Mind you we have not really given it a fair shake since then as I stopped by the hobby shop and picked up an OS so I could fly the next day as I needed the practice. So It sits on the shelf for now. Might be the carb swallowed something in the air...not sure.

I may look this engine over again tonight and see If I can find the issue. But the first 3 flight were fine. The engines look well made too.