Air box modification on CRF 250X
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Sat Jan 06, 2007 6:11 pm

    I AM BACK IN THE SADDLE AGAIN!!!!!!!!!!

    Just an update, I put a 158 jet in and screwed my fuel screw in all the way and backed it out 2 turns, modified my air box per AS's sheet above and put the White Bros. E2 Exhaust on and it screams!! Thanks AS!!

    Every now and then if I twist the throttle real fast there is a slight hesitation real early in the rpm's but at least I am back riding again.


    Thanks Again,
    -Randall
  • User avatar
    NCLR1
    Posts:465
    Joined:Sun Dec 24, 2006 7:20 am

    by NCLR1 » Tue Jan 09, 2007 2:00 pm

    I am not the authority on jetting, but if you still have a little bog in the low end of your throttle you should take a look at the pilot jet. I am sure that you have a 40 slow jet, I am experiencing the same problem. I am going to switch to a 42 and see how it goes. That is also the advice of most of the members here. Going to a larger number slow jet will allow you to adjust the fuel screw and idle more if you are running out of turns. Good luck and make sure to update your results.
    Tony C
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    JimmyPwadd
    Posts:105
    Joined:Mon Nov 20, 2006 8:26 am

    by JimmyPwadd » Tue Jan 09, 2007 4:46 pm

    I went to a 162 main, 42 pilot and did the AP Mod. plus the others listed below.
    Made a HUGE difference!
    2006 CRF250X
    Pink Wire/Air Box/Baffle Mods/ Removed B.F. Screen
    Boyesen Quick Shot /AP mod
    JD Jetting Red Needle Clip 4th Pos.
    162 Main/42 Pilot/Zip Ty Fuel Screw 2-1/8 turns out.
    Moose Handguards & White Bro.s Skid Plate
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Tue Jan 09, 2007 7:12 pm

    Thanks Tony and JimmyP,

    I will go ahead and change the slow to a 42 and let you know what it's like...

    -Randall
  • User avatar
    rstappenbeck
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    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Tue Jan 09, 2007 7:13 pm

    Tony and JimmyP,

    What is your elevation where you live or ride?

    -Randall
  • User avatar
    NCLR1
    Posts:465
    Joined:Sun Dec 24, 2006 7:20 am

    by NCLR1 » Tue Jan 09, 2007 8:22 pm

    I live and ride under 3000.
    Tony C
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    JimmyPwadd
    Posts:105
    Joined:Mon Nov 20, 2006 8:26 am

    by JimmyPwadd » Tue Jan 09, 2007 10:08 pm

    Same here, anywhere between 700 & 3000 feet.
    2006 CRF250X
    Pink Wire/Air Box/Baffle Mods/ Removed B.F. Screen
    Boyesen Quick Shot /AP mod
    JD Jetting Red Needle Clip 4th Pos.
    162 Main/42 Pilot/Zip Ty Fuel Screw 2-1/8 turns out.
    Moose Handguards & White Bro.s Skid Plate
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Thu Jan 11, 2007 10:07 am

    I am at about 685ft
    2006 CRF 250X

    White Bros. E2
    158 Main Jet
    42 Low Jet
    Air Box Opened
    JD Jet Kit
    Red Needle
    5th Clip Position
    Elevation 685 Ft. Above Sea Level
    Avg. Temps from 91(Summer) to 28(Winter) Degrees.
  • User avatar
    NCLR1
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    Joined:Sun Dec 24, 2006 7:20 am

    by NCLR1 » Thu Jan 11, 2007 1:18 pm

    rstappenbeck wrote:I am at about 685ft



    Did you do the AP mod that was listed with the JD kit? It is really easy to do.
    Tony C
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Fri Jan 12, 2007 5:11 pm

    Did you do the AP mod that was listed with the JD kit? It is really easy to do.


    It's fairly easy,

    First you take off the side number plates, then the seat. Next take the rubber strap off the battery, then pull the battery up and out gently and the black plastic coating that has the wires in it and lean the battery off the right side of the bike, then you will be looking at the top of the air box and snorkel with metal band over it. Once your looking at that move the metal band forward with your thumbs and peel the rubber feeling top off of the air box it should just peel right off since it is only held on with rubber cement. In the directions for modifing the air box it shows how to cut the whole top off but I did NOT do that, I left the box in place and once I had the rubber top off you take a small drill bit and there will be two rivets that hold the metal band in place just drill straight through the center of those and the band will come right off. Then you will have room to work. You should be looking at the open snorkel with the two rectangle holes in it, there might be a better way but I found it easy to take a DRIMMEL tool and cut the three plastic ribs off the top of the box so it is flat on top. Then I took a utility knife with a new blade and used a propane hand held torch and heated up the blade til it was red and cut the top of the box off. It made it easy with the hot knife. You will be able to imagine a line that goes around from the front of the box along the sides and across the back right in front of the metal battery brace. I didn't feel like it was nessacary to open the whole top of the box since the battery would be covering the back of the box any way. It seemed pointless to me, but you can do which ever will work for you. Be sure when putting if back together that you tuck the black wire tube back in between the rear fender and the metal battery brace. Hope this helps

    -Randall
    2006 CRF 250X

    White Bros. E2
    158 Main Jet
    42 Low Jet
    Air Box Opened
    JD Jet Kit
    Red Needle
    5th Clip Position
    Elevation 685 Ft. Above Sea Level
    Avg. Temps from 91(Summer) to 28(Winter) Degrees.
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Fri Jan 12, 2007 5:15 pm

    One more thing when you do the air box if you do not go to the Honda store and buy a 158 main jet and a 42 low jet each just a few dollars, then the amount of air that you bike will pull will completely over take the factory jetting and if will fall flat on it's face with any throttle. It will idle but probably not be able to ride it. The main jet is real easy to replace!!!

    -Randall
    2006 CRF 250X

    White Bros. E2
    158 Main Jet
    42 Low Jet
    Air Box Opened
    JD Jet Kit
    Red Needle
    5th Clip Position
    Elevation 685 Ft. Above Sea Level
    Avg. Temps from 91(Summer) to 28(Winter) Degrees.
  • Halen
    Posts:362
    Joined:Sat May 13, 2006 4:32 pm

    by Halen » Fri Jan 12, 2007 8:30 pm

    I agree with a few of the buds before me... I am currently running a 162, 42, red#5 and cut airbox. Those combo's along with a FMF powercore ti made it like riding a brand new bike!
    09 CRF 250R
    RMR lowered suspension
    Heavily armoured for the bush
    50 tooth rear
    soft gel seat
  • User avatar
    NCLR1
    Posts:465
    Joined:Sun Dec 24, 2006 7:20 am

    by NCLR1 » Mon Jan 15, 2007 7:39 am

    This was the first weekend that I have been able to go out and try out the new jetting. It was very nice. The only problem I had was the bike would cut off randomly when it was warm. It might have been do to the very cold weather this weekend at Ocotillo. Other than that, it rocked.

    158 main
    42 slow
    red needle 5th clip
    AP mod 1
    WB E2
    Tony C
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Tue Jan 16, 2007 6:34 pm

    Hey Tony,

    I had exactly the same problem.

    I road my bike Saturday also, after my bike was hot it would cut off when I went to give it gas. It happened probably 20 or 30 times in 5 hrs. Does anyone know how to fix that???
    Last edited by rstappenbeck on Tue Jan 16, 2007 6:40 pm, edited 1 time in total.
    2006 CRF 250X

    White Bros. E2
    158 Main Jet
    42 Low Jet
    Air Box Opened
    JD Jet Kit
    Red Needle
    5th Clip Position
    Elevation 685 Ft. Above Sea Level
    Avg. Temps from 91(Summer) to 28(Winter) Degrees.
  • User avatar
    rstappenbeck
    Posts:37
    Joined:Sun Dec 31, 2006 6:51 am

    by rstappenbeck » Tue Jan 16, 2007 6:39 pm

    Tony,

    I'm wondering if we go to the 162 main like Halen if that will fix that problem?? What do you think Halen did you go straight to the 162 or did you try something smaller first?

    -Randall
    2006 CRF 250X

    White Bros. E2
    158 Main Jet
    42 Low Jet
    Air Box Opened
    JD Jet Kit
    Red Needle
    5th Clip Position
    Elevation 685 Ft. Above Sea Level
    Avg. Temps from 91(Summer) to 28(Winter) Degrees.

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