Can a rich mixture cause backfires thru the carb

[Under Dog]

I'm still fighting an occasional backfire through my left carb, usually as I ease the throttle up to about 1800rpm. I know a lean mixture can cause a backfire, but I've checked everything for air leaks and it all seems sealed up tight. I've got my mix screws out about 4 turns, which I would think would be on the rich side.

Can too rich a mixture cause a backfire?

 

[Sandrew]

Sync the bastards.

Also, adjust mixture screws individually to get equal plug colors, my right one was backfiring, too, at first, when they screws were both 3 turns out, I added 1/2 turn to right one, problem solved.

 

[willem]

yes too rich a mixture can cause backfires If you have too little oxygen in the cylinder, not all the fuel vapors burn up when sparked. Once the valves open again, there is air available over there so the flame goes where the air is: backfire!

what are your plugs telling you? No air leaks and 4 turns out on your mix doesn't necessarily mean you're running rich