The FA80 is one of Saito's earlier engines. It does not have enough power for the UCD.

The Evo 46 sounds like the low end is rich. Try this: remove the glow driver and let the engine idle until the RPM start to drop, but before the engine dies, pinch the fuel line with a pair of long-nose pliers.

If the RPM slowly increase and the engine continues to run for several seconds, it is too rich on the low end. Remove the blue collar next to the carb and turn the low end screw clockwise about 1/8 turn. Start the engine and see how it idles. Each time you do this, bring the engine to wide open and readjust the high-end needle. Repeat until it idles properly.

Props: a longer prop with a smaller pitch will act like a lower gear in a car. You will get less speed, but more power.