09 yz450f low throttle

4 replies to this topic
  • blakers213

Posted October 04, 2010 - 09:29 AM


I asked greyracer couple months back about my new 09 yz450f running rough at 1/4 throttle and he suggested unplugging the tps and this worked. I did order a new needle for the carb but after 3 months on back order I gave up. Since then I have ridden the bike and on a fire road and in 4th and 5th gear at 1/4 throttle it was horrible, very rough. I looked on JD jetting web site and on the FAQ section it descibed this exactly but about the Wr450's and he even mentioned unplugging the TPS. it went on tho say this is normal and this was to prevent the bike from over-heating and it is an ignition thing. Is this true because it is very annoying? I know these bikes are not made to be ridden at a steady 1/4 throttle but sometimes it happens and you would think it would affect the acceleration going through that point of the power.

  • redchief31

Posted October 04, 2010 - 06:38 PM


Did you have trouble with the throttle acceleration as far as it being very boggy till about quarter throttle? I have an 09 and i'm having an issue with that and am curios as if unplugging the tps will really work and not have any issues or cause harm to the bike?

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  • blakers213

Posted October 05, 2010 - 05:30 AM


As far as I know there willl be know damage for leaving the Tps unplugged for a extended period. Mine isn't a bog it just runs really rough if held at 1/8-1/4 throttle.

  • podiumjoe1

Posted October 07, 2010 - 09:23 PM


Your TPS may be off. You can get the tool to check it's output voltage and set it, by going to Simon Smart Body on Facebook. The FCR's need to be set at 3.99 v - 4.00 v at wide open and then then have .040 under the wear plate when closed. This is how the FCR was designed to work. All else will fall into place then. After this, jetting is easy.

  • blakers213

Posted October 08, 2010 - 05:08 PM


Thanks, I'll try anything.

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