Hears the deal.....I have a 1969 gas engine with a Zenith Carb. Tractor starts fine but will not idle smooth. Seems like the engine is gasping for Air? Under throttle the motor boggs down and will die. Have rebuilt the carb twice now and still no better. No obstructions in the air intake. Replaced the fuel filter, ignition and oil. Voltage regulator is showing ranges from 7 to 12 as the engine rpms changes irregularly. Checked the distributer shaft bushing and all seems well with that. Any ideas to whether or not this is a air, gas or electrical problem?