[Gearhead999]

Backfire, through the carb means LEAN.

If the carb is NEW, first I would check the float levels. If they are set wrong, high or low, you'll have a problem. Low would cause lean, not enough fuel, backfire and shut off.

Next, check for vacumn leak. Carb base, old hoses, etc.

Then check fuel filter, you are running one, clogged..no good

Check fuel pump for pressure and volumn.

Hope that helps...