I have a YZ400F and I'm having a hell of a time setting the carb up. The bike starts easy with the choke on. As it warms up the idle climbs. It doesn't matter where the idle screw is set because the only way it will idle with the choke off is with the idle screw all the way in as far as it will go. I know this is not correct but all attempts have failed. There is also a bog off of idle with a small amount of backfire. I'm at 900Ft, stock exhaust, open air box, and use 93 octane. The carb has been cleaned with a fine tooth comb as well. Any help would be greatly appreciated.