Steady Rough Runner

4 replies to this topic
  • shotgunscott

Posted April 26, 2003 - 12:43 PM


First of all thanks to every one who takes the time to reply to the questions and share there knowlage and opinitions. I've been a member for about 6 months but this is my first post.
At a steady throttle position starting at aprox 2500 rpm's and above the bike starts runnng rough like a richly jetted two stroke,(daa-da-da-daa). The problem happens both under load and while sitting with the bike in gear so the rev limiter would not be a factor. I have been through the entire jetting spectrum from extremly lean (1 3/4 P.S,42 P.J,3rd clip position, 140 main) to way fat (3 1/2 P.S,50 P.J,5th clip position yz needle, 170main) i have tried different blends of fuel from 92 pump fuel to 114 canned fuel, different custom exhaust tips from varing degees of restriction, gray wire plugged in,un-plugged, air box baffle in,out. i have had the Yama band aid for the woodruff key performed(didn't need it, valves checked, TPS and coil checked and it still runs rough.
The bike is an 03 450 but if any of the previous years have had a problem like this or if any of you fellow TTrs see an area I may be over looking please reply. What little hair and patience that i still have i would like to save(I have teen age daughters).
Thanks in advance. [list]

  • captain_S

Posted April 27, 2003 - 11:17 AM


I know how you feel,i had a lot of trouble with my 426,but with all the guys on tt that really do seem to have so much experience behind them,i`m sure some one on tt can help you solve it!.Does it feel like a fuel or electrical prob!,take out the plug and give it a check,if it is black put in a fresh one and try again(most important to have a good plug when adjusting jet`s)check the carb is clean and all jets passage ways,blow it through with air,and blow in the breather pipes to check them too, plug cap incase it is loose,or any splits in the rubber cover(if you have been using something to lever it out!)try the kill switch incase it is faulty, maybe even take it out in the dark to see if you can spot a short in the electrics!.Good luck and don`t give up,it`s worth waiting for :)

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  • KiwiThumper

Posted April 27, 2003 - 12:50 PM


Also check the carb boots to make sure they are tight. Air leaking in at higher RPM is not a good thing.

  • Indy_WR450

Posted April 27, 2003 - 02:35 PM


I have heard of the CDI units going and causing this kind of rough in the mid and upper rpm running range. I would swap CDI units with a buddy and see if that is not the problem. I have heard of this happening on one a couple of YZ 450's :)

  • CowboyBob

Posted April 27, 2003 - 02:46 PM


Check to see if the fuel screw fell out


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