I have a Loncin 196cc engine that powers one of our go karts. Within about 15 minutes of use the spark plugs look like this (this one was brand new) and as you would expect it cuts out: It’s not happening to our other engines, I wouldn’t say the other plugs look perfect, but nowhere near this bad. My first thought it slightly older petrol, but even then it’s being used in the other engines too. I’m all out of ideas. Thoughts?