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Thread: main jet shim

  1. #1
    Senior Member greendub's Avatar
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    Last weekend after a jet change my main fell out. Easy fix, but I noticed something. Bike ran great for the five minutes before. Climbing hills better than ever. Anyone ever try to put a small shim on the main jet? I have shimmed the needle, but am not sure if this would work. Looks like enough thread for 1 shim.

  2. #2
    Senior Member Stromper's Avatar
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    I can't imagine what spacing it out would do



    I am not sure if the needle makes it down to the main jet or is riding in its own

    female part



    In either case





    I can believe as it backed out that some gas could flow around the looser threads

    and richen the mixture

  3. #3
    Senior Member PalmStateCrawler's Avatar
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    I would have to assume that adding another shim to the needle or going up a size on the main jet would be a better solution than trying to shim a jet.
    '13 690 Enduro R too many frickin farkles...
    '07 KLX250 farkled (wife's bike)
    '86 BW80 farkled to size
    '10 TW200 you will be missed

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  5. #4
    Senior Member greendub's Avatar
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    Quote Originally Posted by PalmStateCrawler View Post
    I would have to assume that adding another shim to the needle or going up a size on the main jet would be a better solution than trying to shim a jet.
    Agreed! But I am running a 125 in the old style. next size up is a 128 too rich. I run good at 75 plus degrees, but lean under that. Just a thought about the shim there. I spray foam, don't know much about any carb other than tw. Going to take all of my old jets 114 to 122 to a machine shop and have them drill the 114s that i have to 126 and 127. Got er dialed in warm weather, but 125 is lean in cold temps and perfect at warmer and 128 has always been too rich. Played with shims a bunch but never got em right. Now is best yet. Lots of playing since i put the big gun on. Added a db dog to quiet it down, but didn't quit make it rich enough.

  6. #5
    Senior Member greendub's Avatar
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    Quote Originally Posted by PalmStateCrawler View Post
    I would have to assume that adding another shim to the needle or going up a size on the main jet would be a better solution than trying to shim a jet.
    Would it make a difference if it was deaper in the bowl?

  7. #6
    Senior Member srs713's Avatar
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    Quote Originally Posted by greendub View Post
    Would it make a difference if it was deaper in the bowl?


    Yeah... deeper... that is all a shim on the jet would do.



    You would just be that much closer to any gunk at the bottom of the float bowl.



    Changing the float height would accomplish the same thing.



    Stephen S.

    '07 TW200:

    15/50 sprockets, O-ring chain, D2Moto foot pegs

    tweaked carb (127.5 jet, 0.019 needle shim, idle screw @2.25),

    Rubbermaid "Action Packer" on homemade brackets

  8. #7
    Senior Member TWBARR's Avatar
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    Anyone know if fiber washers would hold up in the carb? Or would they fall apart. Thickness is .030"

  9. #8
    Senior Member mhomadness's Avatar
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    It depends... mostly on the fiber material. As long as fuel would not attack it, maybe OK. But given time & vibration, it may degrade. Stick with metal. m.

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