+1 on running C12 since you can’t go wrong there. I ran “100” octane from a local 76 station pump which wrecked the piston and cylinder from detonation in only a few sessions. Turns out that fuel has a 95 motor octane. Recommended motor octane for these engines is at least 100 to prevent detonation.
I noticed I was having this issue this past weekend as well. I agree it may have something to do with the pilot circuit being rich, although it does sound like a lean bog. I’ve pretty much ruled out the main jet and needle since they’re common sizes and slightly on the rich side. The choke knob should only adjust idle, so I wouldn’t suspect that.
I’m in my early 20’s, so no masters for me. Now that you mention it, that does sound like a good way to shake the kart down, I’ll check out the schedule. How about this since shifter numbers are a little low in our area: post in this thread if youre considering an upcoming race. Maybe that will help us being scattered across different tracks. I know I’ll be at the first Sonoma race for sure. Will update if I decide to go to a Stockton race too. I have a stock moto 125 and an icc I can run.