2009 - YZ450F Bogging at half throttle

5 replies to this topic
  • sniper69714

Posted December 09, 2014 - 04:20 PM


I have a 2009 YZ450F, I did an oil change on it and now it bogs down and wont go past half throttle almost like its hitting a rev Limiter, cleaned the carb, I have a JD Jet kit installed, I have adjusted my air/fuel screw tried my TPS plugged in and unplugged I have a video of what it does but im not sure how to upload it to here.


I'm stumped, any help would be appreciated.

  • William1

Posted December 09, 2014 - 04:59 PM


An oil change will not cause a bog. Retrace what you did when you changed the oil to solve what you messed up. Not a jetting issue.

  • grayracer513

Posted December 09, 2014 - 09:33 PM


Let me ask, does this happen when you ride it, or when it's in neutral?

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  • sniper69714

Posted December 10, 2014 - 05:29 AM


William, I retraced my steps, I even did another oil change. I forgot to put in that as soon as my oil change was complete the bike was much much easier to kick over. I did a leak down test a d my compression is around 95-98%.

Grayracer513, it does it in both neutral and in gear at the same RPM

  • grayracer513

Posted December 10, 2014 - 07:24 AM


Try this:  Find the light blue wire that runs up the frame from under the left side of the engine to the steering head.  There should be a connector there; unplug it and see if it clears things up.  The wire runs to the neutral switch from the CDI, and if it gets grounded, the CDI will think the bike is always in neutral.  When in neutral, the rev limit is lowered to 7000 RPM to prevent squids from blowing it apart with no load, free rev goonery.

  • sniper69714

Posted December 10, 2014 - 01:53 PM


Hey Grayracer 513,


I tried unpluggin it with the TPS disconnected, it wouldnt even try to start, I tried it with the TPS connected and it wouldnt even try to start, I plugged it back in and the bike fires right back up but I still have the same symptom.

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