At the temperatures you are discribing the fuel doesn't evaporate so easily, so it just condenses to the surface of the intake manifold, by pressing the accelerator pedal 2 times, you activate the autochoke and pump extra fuel into the engine, so it will start better. Autochoke can be checked by removing the airfilter and, with a cold engine, pressing the accelerator pedal, in good condition, your autochoke should then engage wich can be observed as the top butterfly valve in your carb closes. Any adjustments can be made by loosening the autochoke housing and, with pressed accelerator pedal, rotating the housing so that the valve closes to a gap of +/- 6mm. For the adjustment i allways use a 6mm drill.

__________________