FWIW:
This morning I decided to check my 2014 carb. settings.

60-65* F  4000' elevation,  900RPM idle, on tach., mixture screw 2 turns out  = highest idle speed.  According to Suzuki 1 and 1/8 is standard. Pilot jet 52.5, needle raised .035" by shaving the plastic washer. I get no backfiring during operation and the plug looks good to me. I don't run on the main jet much but the jet is 145. Sometimes if I shutdown carelessly it will after-fire but since I run the carb dry this doesn't happen of course. I like to run the idle at about 1800 RPM because the engine seems to like it. " it speaks to me" Also, I get close to 60 MPG.

My observations as strictly an amateur.