Needing some help and hoping the experts here can help. My 544 is overheating and I've done everything I can think of. I've flushed the cooling system, replaced the thermostat and radiator cap, burped it and added an electric cooling fan. I verified the gauge is accurate with a separate temp gauge (reads in the 200s when it starts to overheat). I know the Coolant is flowing when I pulled a host to the heater. I checked the timing and rebuilt the carburetors. It takes 30 minutes to overheat usually. I think its running too lean but have the nuts on both carbs nearly 3 full turns and it still bogs down when I lift the piston for the setting test. Short of rebuilding the motor, what could I be missing?