Check your throttle linkage! When I did my first start-up last week, my idle shot up like that after the fourth or fifth time starting. I had to use the kill switch to shut my cb down. I found the set screws for the throttle cables had worked loose from vibration, and the fact that I had never tightened them down. You mentioned that the throttle was difficult to twist when on vs. off. That's weird. If it was difficult to twist irregardless of the bike being on or off, I'd say it was definitely the cable/linkage.