My YS 63 FZ is rich on the bottom end but runs lean on the top end. It seems to get a bit leaner as the flight goes on. I'm not sure what to try to correct this situation. I am using the 63 to power a Pheonix Models Extra 300 and when the engine runs well, I am pleased with this combination. Any suggestions on what to try to fix this condition?

Thanks in advance for any suggestions.

Heli-NuBee (Roger)