I think it is critical to use a really good oil in the fuel. A really good synthetic oil for air cooled engines. Do not use the inexpensive oils. I currently use Stihl HP Ultra. Red Line and some others would work too. Earlier I used Amsoil Saber oil, but it was leaving more carbon deposits than I liked to see. Also use 20:1 fuel to oil ratio maybe a little more for initial break in. The connecting rod needs all the oil it can get and it may be a little too tight initially as well. Don't try to go with the lean oil mixtures as the engine cannot handle lower oil ratios. The bushed rod is the weak link and will fail with lower oil ratios.

The Evolution engines work really well, plus they have needle bearings on the connecting rod too. Evo tested their engines much more rigorously than NGH did. OS of course did the same too. The Evolution 10cc gas engine is pretty awesome, it develops a lot more power than the NGH 9cc engine does.