I've got to sort out a Norvel 25. I got it used and put it on a GP combat Spitfire. It ran great on the maiden, but I didn't set the throws, talk about squirrelly!!!!!!
Anyway, second flight a week later, I couldn't get it running correctly, surging at full throttle no matter if rich or lean.
There was ht rtv around the carb when I got it, but I'm thinking air leak, although I could have sworn I saw the carb suck in some grass debris. Not sure
On the maiden, you didn't have to throw it, it would pretty much fly out of your hand.