Spark plug and piston after 8 hours

[Wypipo]

I know it?s pretty early but I just put an RK tek head in so had everything apart so I figured I?d take some pictures and get opinions...I don?t have a ton of experience. I broke the bike in proper for the first 5 hours. About the 6 hours in I was riding through a recent forest fire and was in about of foot of thick wet ash for a good hour. The bike started to overheat so i let it cool down and everything was good after that. I did lose a little bit of coolant from overheating, maybe 4 ounces or so. Here is a picture of the top of the piston and the spark plug.
Picture of the piston before and after cleaning with a rag and the underside of the head

 

[Wypipo]

And the spark plug before and after cleaning

 

[(F5)]

I could conclude all sorts of things from those pictures but I'd be fooling myself.
The only way to do it is a very long straight flat out in top sustained then pull the clutch cut engine coast to stop then open it up. That will tell you about the mainjet size.

Not a hugely useful tuning method on a dirt bike. Essential on roadrace bike until egt meters made that redundant mostly.