Rub off the chunky stuff with a piece of wood or plastic and then sand it with something like 100grit paper. Do NOT sand the sides or round the corners. Just polish the black off the top. If you cut back on the oil and use synthetic the chamber will not soot up:
Many many highway miles on that right hand cylinder, 40:1 Ipone synthetic with a lean fuel mixture.
This is a well worn Blaster 2 stroke, jetted rich but still 40:1 Ipone Synthetic.
Shiny glob is a bit of oil dropped on during disassemble.
4 shiny lines at corners are mixture wash blank areas from edge of ports.
As you can see, soot wipes off with a finger or rag even after a year of running.
This is what the head looks like:
My point? Use synthetic at 32:1 to 40:1 and jet proper for less carbon.