08 CRF250R Athena Big Bore Jetting.
  • Crasha
    Posts:3
    Joined:Mon Dec 15, 2014 3:03 pm
    08 CRF250R Athena Big Bore Jetting.

    by Crasha » Thu Apr 09, 2015 1:50 am

    Hi All,

    I have recently purchased a 08 CRF250R second hand and put an Athena 280 Big Bore kit and replaced the intake valves and springs with Pro-x stainless units. I didn't get the valve seals recut I just blued them up to check the contact area and it looked good so I lapped them in. It fired up straight away and rides pretty sweet now.

    I have been looking into the jetting for this set up as I have heard these bike run pretty rich from the factory.

    This is how I found the carb settings;
    Pilot: #42
    Needle: NMTS, 3rd from the top
    Main: 188

    I did some fine tuning and this is how it is now;
    Pilot: #40
    Needle: NMTS, 3rd from the top
    Main 188
    Mixture screw: 1 3/4 out

    Does this sound about right? The more I research this the more confused I get as there seems to be a few different stock set ups depending on where in the world you live.

    Cheers
  • Crasha
    Posts:3
    Joined:Mon Dec 15, 2014 3:03 pm

    by Crasha » Thu Apr 09, 2015 1:53 am

    I should also note, I live at sea level in Australia and I run 98ron fuel.

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