Sudden RPM drop at 5-10% throttle position.
  • motomahem83
    Posts: 1
    Joined: Fri Jul 07, 2017 2:50 pm

    Sudden RPM drop at 5-10% throttle position.

    by motomahem83 » Fri Jul 07, 2017 3:13 pm

    Hello everyone! I have a problem with my 2009 CRF450x Supermoto and I'm hoping one of you guys can help me figure it out. I have been having this problem with this bike for some time now and can't seem to eliminate it no matter what I try. The throttle is smooth accelerating from 5-10% to WOT and smooth decelerating from WOT to 10-5% then there is a sudden drop to idle on the last little bit of the throttle movement. Also when I am crusing around and let off the throttle then ease back on there is a sudden jerk forward... Hopefully that made sense. I have struggled to fix this for so long I have drawn up a diagram in paint to illustrate it. The bike has done this ever since I bought it used a couple years ago. It's not a huge deal but I would think that the throttle should be smooth all the way from 0% to 100% and not lunge forward when I barely touch the throttle while cruising. Any help is greatly appreciated!

    The slack in the throttle is set to about 1/8" of free play
    Altitude: 600-1000 ft
    Main jet size: 155
    Pilot jet: 42
    Leak jet: stock
    Needle used: NCVS
    Clip position: I've tried 2nd and 3rd from top
    Airbox mods: top half way cut out and side vents cut
    Air Filter changes: none-Stock
    Exhaust: FMF Powerbomb header and pipe baffle out, fresh copper gasket
    TPS sensor IS plugged in, tested and in spec
    Chain is not loose and set to correct amount of slack.

    I have even installed the G2 Throttle tamer and it helped a tiny bit but did not fix the issue..
    http://www.g2ergo.com/store/g2-throttle-cam-system/
    You do not have the required permissions to view the files attached to this post.
  • Aussiecrf230
    Posts: 1962
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: Sudden RPM drop at 5-10% throttle position.

    by Aussiecrf230 » Sun Jul 09, 2017 4:39 pm

    Looks to be a bad transition from the idle circuit to the main circuit. So it happens as you get back on the throttle after a period of deceleration? Is it like it goes flat before accelerating normally? Does it idle ok? Have you tried opening the idle mixture screw say quarter of a turn and see if that helps? Where is your fuel screw set at the moment? Have you tried a 45 pilot jet? Sorry lots of questions just trying to get my head around the problem, nice diagram which makes me think transition. Perhaps accelerator pump needs to cut in earlier to cover the hole. I would be looking at idle circuit first if only to eliminate it from being the problem.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas

Who is online

Users browsing this forum: No registered users and 2 guests