Tunning nitro can be a bear it your engine is locked up its because you were lean not enough fuel in the winter we get good air nice and dence so you need to fatten up the engine add more fuel i generaly fined im one to two turns richer over the base line manufactures sugested settings ie. If main needle is suposed to be 2 1/2 turns out from closed i start at 3 1/2 - 4 turns and its opposite on real hot muggy days in july also when snow gets on the heat sink it can be a pain as engine dosent get to a good operating temp good luck on finding what you want