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Thread: Jetting ATV Carb

  1. #1
    Less posting, more wheeling! joshs1ofakindxj's Avatar
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    Jetting ATV Carb

    I'm sure someone knows how to do this...

    So I put a 2" PVC snorkel on my 1999 500.

    http://photos-b.ak.fbcdn.net/photos-ak-snc...993521_1767.jpg

    The motor runs fine until the higher RPMs near WOT when it bogs down.

    The motor also has some white exhaust smoke now and then. No overheating issue since I moved the radiator and fan. New spark plug and clean carb.

    I ordered a Dynojet stage 1 jet kit.

    Today I put in the Dynojet needle and put it on the 2nd groove for less then 5000ft since I don't ride anything higher than 3000 ft.

    The main jet that came out had 145 on it. I put in the dynojet 134 and the motor bogged down much sooner. Barely half throttle. I wasn't sure if the numbers matched up with the stock one so I tried what dynojet recommended to start with. I would say I went in the wrong direction and gave it too little fuel. I guess I need a larger jet than stock.

    If the stock jet and Dynojet numbers are equivalent then I'm going to need larger jets than what the kit has since it only goes up to 142.

    What size should I try and where can I get larger, accurately sized jets if I need them?

    Should I be changing the jet that is in the top of the carb (pilot jet?)?

    Thanks for any advice.

  2. #2
    PghOffRoad Regular
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    You need a larger main jet . Im not sure what size, start with a 150 , 155 , 160 .
    Most dealers will sell individual jets , just match them up

    reference this:
    http://www.atvstyle.com/index.php/jetting
    http://www.atvriders.com/articles/jetting.html
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  3. #3
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    x2 or buy a tune a jet there so much nicer
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  4. #4
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    also with jetting an atv ... you need a better then stock exhaust. just went through this issuse with honda repair shop.

    larger jets and stock exhaust will cause bogging and dont do any steep hills .. you will not make it. also the computer may need upgraded aswell. cause the computer and exhaust and carb all need to be tuned to each other.

    hope this helps some.


    i just had stock jets put back in my honda rubacon 500 cause previous owner have upgraded to larger jets and computer / exhause ... he kept the computer and exhaust and put stock back on ... had boggin issuses.

  5. #5
    Less posting, more wheeling! joshs1ofakindxj's Avatar
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    I don't think I have a computer that controls anything fuel related.

  6. #6
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    Quote Originally Posted by joshs1ofakindxj View Post
    I don't think I have a computer that controls anything fuel related.

    i'm sure you do. double check with a dealer .... mine was located on rear of atv between "glovebox" and rear rack. could not see it til ya take the box off.

  7. #7
    Less posting, more wheeling! joshs1ofakindxj's Avatar
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    I have no wires running to the carburetor...I don't know what any computer could do for the ATV.

  8. #8
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    there's no wires to my carb either ..... call a dealer and ask them about it. they can tell you for sure.

    just tellin ya from my experience .....

  9. #9
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    You need to learn to read the spark plug. The color and shading of the plug will tell you which way you need to move the jet. Run it to the rpm it is rich or lean at then shut it off and read the plug. Adjust accordingly.

    And it has an electronic ignition, but that's as close to a computer as it gets.

    Jetting is easy, just takes some time and patience.


    Also with that much restriction, you may never be able to get it right. Might need to go to a larger size pipe.

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