Newbie yz400 questions

2 replies to this topic
  • wykyd450r

Posted April 25, 2012 - 07:33 AM


Recently picked up an 98 400f. Its been sitting in the barn for quite awhile before I bought it. After bringing it home, the fuel was changed and the bike cleaned up. Anyways, I notice that there seems to be issues with it. It has a miss, sometimes a backfire when you try to idle it. If you begin to open the throttle up a little, it is fine from there to high end RPM's. It almost seems as if its ideling too low, so I tried to raise it a little with the black knob, but no amount of adjustments in either direction seem to make any change in RPM. Upon inspection, I believe the little black "arm" or "linkage" on the right side of the carb ( I guess operates the diaphram ) wasnt functioning right. It seemed to been frozen. I moved it with a screw driver until it free'd up. I am wondering if the pilot jet may be clogged from sitting, or a simple adjustment of the air/fuel mixture screw would be a fix. I am new to the FCR, so I dont know a whole lot about it. I been riding quads the past several years, and none had the FCR. Sorry to be such a newb, but hopefully someone is wiling to help me out. Any help is greatly appreciated. Thanks.


I also noticed that when you "push" the throttle forward to close it all the way, it dies.

Edited by wykyd450r, April 25, 2012 - 07:34 AM.

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  • banda

Posted April 25, 2012 - 01:37 PM


I suggest a complete carb cleaning and new jets. The accelerator pump and the pilot circuit are the first things to gunk up when this carb sits. If you are not riding at least once a month, get used to pulling the carb off and cleaning it.

  • Slow and Jerky

Posted April 26, 2012 - 04:15 AM


Most likely you will need to pull it and clean the jets, but you try running some Sea Foam through it first.

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