Engine spudder?

Ive knoticed that the engine runs a lil weird when it cold/hasnt started in a week or so. When i first fire it up and give it gas the engine dosent respond to throttle very well. My suzuki vinson would do the same thing. Once its been idoling for a minuit or so its fine. I washed the bike last sunday after riding. I fired it up and gave it a few blips of throttle in nuetral and it was doing the same thing. So i throttled it up till the point where the engine didnt respond to more throttle n held it there for about a second, then it made a weird pop noise and reved up and didnt do it again after that. What is the reason for this. My vinson was carb with jetting and other work done so i could understand y it was cold natured but this fuel injected bike shouldnt do. Keep in mind im in florida. Ambiant temp was about 84 on sunday