Strange cold start and idle

:huh: Got the 83 KZ750 Spectre out for a spin. It usually cold starts best with no choke and lots of juice. Then after a 5 minute warm up I have to put aobut 1/4 to 1/2 choke on her to get smooth above 4-5,000 RPM. Then I have to leave the choke in that position. It seems to be lean at cold start and then rich at warm up. But really I'm just guessing.
Any ideas?

Dirty jets, improper float height, choke malfunctioning, etc...

If your starting it without a choke when cold, it is rich not lean, if you have to up the choke when hot then it is lean. I can only guess as to why you get a rich mixture when you open the throttle as it should supply the correct fuel/air mixture for the throttle position.

Is this something new or has this been the problem since you've had the bike? What happens when you use the choke when cold/