spark plug reading

Timing, heat range and A/F ratio all seen on the spark plug quite a few online articles about this, I thought I understood it but when I took My plug out I couldnt do it as accurately as I thought. Do we have any plug experts on board?

This is about 40 miles on new plugs, do they tell a story?

no expert, but mixture too rich

slightly black , means too rich , normal should b a grey/brown same as your tail pipe after a run. if its very white and glazed then thats valve timing or week mixture .

I managed to get a bit of colour on the insulator by changing heat range one step colder, it now has a bit of a tan
I need to get it hot to see if that has stopped the engine dieselling