Have you tried tweaking your idle speed up a 1/4-turn, or opening the throttle just a crack while you crank?
My Trophy responds to a slight throttle opening after a couple of cranks, and the first indication of fire. The manual says to leave it alone. But I would prefer to have it start. My XS400 is the same as it gets colder. My SV1000 Suzuki also the same. The 79 Yamaha is the only one that fires right away, and does not require any throttle.
All have carbs except the Suzuki which is FI with a magic box. ECU I suppose.
We have come a long way from tickling the carbs and push starting.