i just bought a 04 450r I bought it with the carb off of it and after i put it toget her the bike would not idle unless the choke was on. i took the carb all apart and found nothing wrong, so i pulled the metering rod all the up and got to it idle with the choke off. i just rejetted it (the metering rod is still all the way up) and now it idles and starts fine, but if i throttle anything over idle it backfires out the exhaust. i have checked the valves and they are fine. i have never owned a 4 stroke and i am not sure what else to do.... also are is there any air fule adjustment screws on these bikes or just the idle screw?