What %nitro are you running? You should be running a minimum of 15% preferrably 20% with 20% oil. Do you have an OS type F plug in it? If not, get one of those and install it. I have ran quite a few NCs and one of them I had to install an extra head gasket. I don't care what I did, it would kick the prop off. I lowered the compression and it stopped. Remember these are supercharged engines. High compression plus the boost can be bad! NC's had alot of carb problems. It could be that the hole in the butterfly is too small, but this mainly affects idle. There is not really and idle adjustment on these engines, and I have found that in hot weather, they tend to load up at idle and nothing will fix it. The large brass weight that is in the regulator housing is not needed either. That can be taken out and left out.