I've got a CR250 99', when I start up from cold,choke on. She revs really hard, and I have to use the kill switch to keep the revs down, once the revs have settled (about 10 secs), it will start perfectly fine,and not rev. If i pull the choke on after it has settled the revs only rise slightly and it richens as you would expect.
The only other sympton i might have, is that i have to keep blipping the throttle at idle to keep it running (every 10-15 secs) but am not sure if this is a trait of competition bikes as this is the 1st crosser i have owned.