I had an NGH 17cc when they first came out.
I had some issues with it from the beginning and the factory sent me the carb spacer which improved things somewhat but i eventually got tired of how inconsistent it was and removed it from the plane.
I'm now using an OS GT15 gas engine in the same sized planes and that is the best engine i have ever owned when i consider things such as ease of starting, consistent running and ease of tuning. The OS is more expensive but the lack of fuss adds up to more enjoyment and more flights which for me is exactly what i'm looking for.