Popping generally indicates a lean condition. Close the choke and crank the engine a dozen times, make sure fuel is being drawn to carb. Turn off ignition and pull the plugs. Are they wet or dry? I'm guessing dry and if so make sure the choke is fully closed. If plug is wet, check the gap. If OK try a new plug. All above assumes the ignition and fuel are OK and the battery supply for ignition is good. Good luck, red