Carb Woes

1 reply to this topic

Posted April 05, 2006 - 04:38 AM


:bonk: 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. :thumbsup: :confused: :thumbsup:

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  • shanedut

Posted April 05, 2006 - 07:07 PM


It sounds like you could be a little rich on the pilot jet. Is it a backfire or a popping. If you have a backfire i would say our too rich on the pilot jet or you need too adjust your fuel screw out. If its a popping you are probably too lean and need to do the opposite. If you have your fuel screw out more than 2.5 turns you need to go up one size on your pilot jet. If you have it in farther than .5 turns you need to go down one size on the pilot. As for the idling problem it could be an exhaust leak or from the jetting.

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