Backfire? ops...........If it keeps backfiring...... timing chain. Check with timing light ASAP. If not, as said, vacuum. If not, as said, plugged fuel delivery system....filters, lines, tank screen, carb (accelerator pump), bad gas, gas cap/tank vent, FUEL PUMP.
Does not sound like electrics (now that makes it electrics).
First: see if dripping, squirting, dribbling gas down throat keeps it from dying. (in other words: manual fuel injection). and we always say check to see if carb squirts with motor off.
Don't start too early tomorrow, you will scare off Santa Claus.
