Plug Fouling
  • kcorey
    Posts:3
    Joined:Sat May 19, 2007 1:10 pm
    Plug Fouling

    by kcorey » Tue May 22, 2007 6:05 am

    What would cause dry black soot on the plug, specifically on the CRF70F and what can I do to avoid this?
  • Asmith
    Posts:14381
    Joined:Mon Apr 10, 2006 7:52 am

    Re: Plug Fouling

    by Asmith » Tue May 22, 2007 6:22 am

    kcorey wrote:What would cause dry black soot on the plug, specifically on the CRF70F and what can I do to avoid this?


    Too rich a mixture.

    What is the condition of the air filter?? Once it becomes partially plugged with dirt and dust, the mixture becomes rich. Are you cleaning it every ride?
  • kcorey
    Posts:3
    Joined:Sat May 19, 2007 1:10 pm

    by kcorey » Tue May 22, 2007 6:52 am

    I just got the bike last weekend for my son, second-hand. I cleaned the filter (it was terrible) but the bike still sputtered a bit, especially at full throttle. I adjusted the fuel/air screw but I think it's wrong because of the fouled plug. I tried adjusting the air screw from your post by first adjusting the throttle to high and then playing with the air screw until the idle sounds good. Is a sootie plug to be expected?
  • Asmith
    Posts:14381
    Joined:Mon Apr 10, 2006 7:52 am

    by Asmith » Tue May 22, 2007 7:10 am

    You will probably need to readjust the fuel/air screw, and possibly move the needle up a clip and or drop the main jet a size.

    Plug should be a light brown.

    This will help.

    http://www.ministothemax.com/hop_ups_carb_tuning.htm

    The jet sizes are wrong as it's written for a 50 not a 70, but the theory is the same. It describes your problem exactly. Also check out their airbox mod. Do it or switch to a UNI air filter for more flow.
  • kcorey
    Posts:3
    Joined:Sat May 19, 2007 1:10 pm

    by kcorey » Tue May 22, 2007 7:16 am

    Brilliant link, exactly what I needed, thanks for the help!

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