Carb issue on 0 to 1/8 throttle (CRF250X)
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    pshailis
    Posts: 12
    Joined: Tue Aug 27, 2019 5:35 am

    Carb issue on 0 to 1/8 throttle (CRF250X)

    by pshailis » Fri Jan 01, 2021 10:53 pm

    Hi guys, I got an issue with the carb. A sudden twist on the throttle (from 0 to 1/8) will stall and shut the engine. Past that point everything works fine and even better than before. I did the airbox, exhaust and pink mod and I installed 158 MJ 42 PJ and raised the needle 2 positions (4th position from the top using stock NKKT) bike pulls better now and power delivery has increased significantly. I only have this issue. I guess this has to do with the pilot jet so I played around with the pilot adjustment screw, turning it out from 2 up to 2.5 turns but nothing changed. Any suggestions?
    Last edited by pshailis on Sat Jan 02, 2021 8:28 am, edited 3 times in total.
  • Back2-2
    Posts: 1148
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: Carb issue on 0 to 1/8 throttle

    by Back2-2 » Sat Jan 02, 2021 7:51 am

    You did not state which bike size and model you are asking about. Also the altitude you are riding at in relation to your jetting you gave. Good fuel, proper jetting and there should be no hesitation or bog. So Yes, it sounds like your primary circuit needs some attention. Also wiring the accelerator lever "Tye wrap mod" will take that initial slack out of fast movement of the throttle.
    If you are asking about a 450 I suspect you are running lean by your jets stated but that is only a guess without further info.

    One quick thing to try is take the fuel screw to 3 to 3 1/2 turns out [CCW] and see what that does for you. If that improves the 0-1/8 throttle you need to go larger on the PJ.
    Neil
    Black Hills of SD
    Life without Motorcycles would just be boring, really boring
    Honda 450X. Yamaha Tracer GT900. HD Fat Boy. Triumph Bonneville. Yamaha Majesty 400. Yamaha Grizzly. Yamaha Wolverine. Yamaha TW200
  • User avatar
    pshailis
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    Joined: Tue Aug 27, 2019 5:35 am

    Re: Carb issue on 0 to 1/8 throttle

    by pshailis » Sat Jan 02, 2021 8:26 am

    Oops! Sorry I have a 2012 CRF 250X

    Thanks for the tips!
  • Back2-2
    Posts: 1148
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by Back2-2 » Sat Jan 02, 2021 8:56 am

    I do not know standard jetting on the 250's. But I still suspect you are running lean on the primary circuit. Is the jetting you stated standard or have you went up on the MJ & PJ ?
    Try the fuel screw adjustment I recommended and see what that does for you. Don't forget the accelerator mod.
    Neil
    Black Hills of SD
    Life without Motorcycles would just be boring, really boring
    Honda 450X. Yamaha Tracer GT900. HD Fat Boy. Triumph Bonneville. Yamaha Majesty 400. Yamaha Grizzly. Yamaha Wolverine. Yamaha TW200
  • User avatar
    pshailis
    Posts: 12
    Joined: Tue Aug 27, 2019 5:35 am

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by pshailis » Sat Jan 02, 2021 12:50 pm

    I research online and see what most people do for the jetting. Stock is 130MJ and 42 PJ. I went up to 158 but left the PJ the same since that's what everyone seems to do. Are you saying that I have a lean PJ? Should I go up on this too?
    I will do the O-ring mod for sure and also replace the diaphragm since it hasn't been changed over the last 3 years.
  • Back2-2
    Posts: 1148
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by Back2-2 » Sat Jan 02, 2021 3:26 pm

    If you left the stock OEM PJ I would certainly go one up. If you are changing the diaphragm make sure you install it on the correct orientation. Common problem getting those in upside down / backwards and wondering what the hell is wrong.
    Your getting there!
    Neil
    Black Hills of SD
    Life without Motorcycles would just be boring, really boring
    Honda 450X. Yamaha Tracer GT900. HD Fat Boy. Triumph Bonneville. Yamaha Majesty 400. Yamaha Grizzly. Yamaha Wolverine. Yamaha TW200
  • User avatar
    pshailis
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    Joined: Tue Aug 27, 2019 5:35 am

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by pshailis » Sat Jan 02, 2021 11:41 pm

    Thanks Neil!
    So going one up will do any difference on the pilot? Or should i get a 45 instead?
  • Aussiecrf230
    Posts: 1962
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by Aussiecrf230 » Sun Jan 03, 2021 1:53 am

    Go the 45 pilot.
    It seems a popular size for lots of different bikes over the years.

    Makes sense that it takes the same amount of fuel to idle a motor.
    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
  • Back2-2
    Posts: 1148
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by Back2-2 » Sun Jan 03, 2021 6:27 am

    Thanks Neil!
    So going one up will do any difference on the pilot? Or should i get a 45 instead?
    Not sure what you are asking exactly? So I'll take a stab at it -
    Going one size larger on the pilot jet will increase fuel to the primary circuit.
    Which is zero-1/8 throttle.
    Neil
    Black Hills of SD
    Life without Motorcycles would just be boring, really boring
    Honda 450X. Yamaha Tracer GT900. HD Fat Boy. Triumph Bonneville. Yamaha Majesty 400. Yamaha Grizzly. Yamaha Wolverine. Yamaha TW200
  • Leardriver
    Posts: 462
    Joined: Wed May 05, 2010 10:33 am

    Re: Carb issue on 0 to 1/8 throttle (CRF250X)

    by Leardriver » Tue Jan 05, 2021 12:29 pm

    You are getting good advice. When I dyno'd a 250X with a stock 42 pilot, the air/fuel ratio was about 17-1, which is terribly lean. A 45 pilot seems to fix this, and is mandatory with a 250 R cam or a Hotcams stage 1 cam.

    If you told me that the hesitation was a little higher in the throttle position, I would have flashbacks to the '06 model, which has such a lean transition to the needle from the pilot that it mimicked a lean pilot.

    After you get this dialed in, consider changing your needle back to stock or one clip in either direction.

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