Start lean at idle, adding fuel till it will not hesitate when you crack the throttle below the temp you want to race at.
I lean my motor out for warmup till the exhaust temps get up to 950/1000 degrees. That won't happen till the motor starts to warm up a little, I see about 500 leaned out on a cold start and keep leaning it out as it warms. After a run I make sure the motor is hot enough to clear water and fuel out of the oil, somewhere over 180 to 210.