I have a 35cc MVVS gas engine that's only had about 4 hrs running in total and is still slighlty rich. I'm using a 1:40 oil/petrol ratio and the engine appears to be running well but the exhaust residue is thick, black, and has a sticky consistency. I am I right in assuming the residue is caused by the slightly rich settings still? The plug is a nice 'sand' color with no significant oily coloration and I'm using a high quality spec 2stroke oil.

Thanks Bob V