Very High Idle

[teufel_hunden_rider]

Hello everyone. I'm new to the site and new to riding motorcycles. I have only had my 2000 Suzuki gz250 for a few months. But ever since I got it it has been idling very fast once it warms up. Typically it runs well once I start it for the first time that day but after a matter of minutes it idles and runs very high. If I take it past 50mph it goes really high. I turned the black cylindrical, screw like, throttle adjustment that is right next to the throttle handle all the way to the low end as far as it went but that just lets me start it in a somewhat normal rpm but it creeps back up quick.

I've got a few months to fix up my bike before I go to boot camp for the marines and I want to leave a well running bike for my girlfriend to start learning how to ride on since I'm going to get a new bike when I get my first duty station. Any help you guys can give me would be very much appreciated. I would love to get it fixed before I go so I can teach her a bit myself before she does STARS.