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I'm having an issue with my street legal 04crf450r, where the bike likes to stutter and misfire quite a bit when held steady at around 40-60mph, 4500-6000rpm. Below or beyond that it runs smooth. Not noticeable in the dirt or at the track, powerband is smooth and pulls hard all the way through. Just at cruising speed on the street it becomes pretty uncomfortable and shaky. Anyone know how to cure this? And tune the bike for a more street comfortable ride?

Is this something new or always been a problem?

Open up your idle mixture screw slightly. You will be surprised when cruising along even at high speeds how the idle mixture affects things at small throttle openings. If it ends up to rich at idle then a move of clip position may help. Assume you have serviced it recently because an old plug etc can cause problems.