Hi... New from Spokane WA

Just picked up my first Kawasaki.. Been looking for awhile for a bike, truth is I'm a new rider and new to working on bikes. The one i found is my profile pic. .. 1977 kz400D with 14k miles on it.. Haven't decided if i want to fully restore or MOD it and make it a custom job.. Like the idea of trying to keep vintage with a bit of updates.. Bike starts on first kick and the electronic start works, think need to replace battery.. Question is, the owner I bought it from would manipulate a n idle knob when he started it cld.. Choked it to get started and rolled idle up a bit to get it warmed up then rolled back idle once it was warm.. is this common? Is this something that manipulating the throttle can do as well until the bike is warmed up?? Any pointers and help would be appreciated..
Thanks !