2003 Honda XR 125 L "stroke backfires carburator" Questions

stroke will pop and backfire under decelleration when it is lean, or not enough fuel. (Jetting too small in the carburator) But, look at the spark plug for color, white is too lean, black is too rich,

...backfires a 'chuff' sound out of the pipe when kicking it over normally when giving it a bit too much gas. I'm thinking it's timing related and have had a small mess around with it before. I've ...