RE: CRRC Back Fire
Of course , the hall sensor must be set around 28 degrees before TDC when the ignition fires.
I'm not talking about to change TO synthetic from mineral oil.
I've seen some times, engines and carbs clogged by change of syntethic oil of different brands . Before synthetic oil brand change is a good idea to clean the carburetor.
Check the woodroof key also ....
Regards