98 zr 600 idle issue

I've owned many sleds that have always idled up when started cold. They all idled down after warming up. I have a 98 zr 600 that does not idle up at cold start. I cleaned the carbs, and all passages in carbs. The jets are cleaned and are also crrect for the sled. The sled runs great otherwise. What would cause this?

98 zr 600 idle issue