what would be a good starting point for 20-40F degree weather 400ft elevation cpi oofs on a 421 serval i am using a single mikuni 38tm flat slide. i have never ran the motor on gas, in winter, and with a single carb. i am using a single because its my only gas carb that i have. i know 20-40F degrees is a jump in temp but i am hoping to have it jetted damn near good for 20F and a little rich for 40F.