exhaust poping or backfire is due to lean, not rich, especially on throttle let off.


Poping thru the intake, with throttle on, is lean as well.

The other guys are right that say the mixture screw is between the slide and head, and the air screw is between the slide and air filter. Most 4 strokes are mixture screws, and most 2 strokes are air screws...and going by what they are called, when you turn them out, you get more(whether it is air or mixture).

If adjusting the mixture screw, from all in to all out, and there isnt much difference...look for intake leaks, this would also cause backfire (because it would lean out the mixture).