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Thread: 33mm mikuni adjustment

  1. #1
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    33mm mikuni adjustment

    Hey guys,
    I have a kz 1197cc dragbike with 33mm mikuni carbs, I rebuilt motor and only changed compression from 10:1 to 13:1 and had a fresh vlave job, the bike
    Ran 9.80s before and since I put motor back in its only running 10.40s and lost 6 mph?the bike is still consistant and idles good and revs good,
    Looked at battery,coils,wiring,plugs and leaned out carb and nothing helped, I got home and took carbs apart and noticed number 4 carb the idle screw was turned all the way in instead of 1 turn out like the other 3.. what will the screw turned in all the way affect?

    Thanks
    Steven
    Steven Davis

  2. #2
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    What main jet are you running? I would not expect the idle screws to affect anything on top end. Just readjust it so it is equal with the other carbs though.

    Scott

  3. #3
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    I am running a 127.5 now, was two sizes bigger.. that plug is the only plug that's black.. others are good
    Steven Davis

  4. #4
    Senior Member funny1's Avatar
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    When the adjustment screw is behind the slide it adjusts the amount of air being bled into the pilot circuit--so --turning it in would richin it up because you are reducing that air so it will pull more fuel----basicly adjusts idle quality----and how well it transitions from idle to 1/4 throttle
    When the adjustment screw is in front of the slide it adjusts how much fuel passes it-----so turning it in would lean it out because you are restricting the fuels path more-----idle quality and 0- 1/4 transition also
    Should not affect WFO that much but you might be blackening the plug on the return road if you ride it back
    Best way to read plugs for main jet size is shut the engine off going thru the finish line and read them before it ever has a chance to idle again
    I can't get my horse to wake up.

  5. #5
    Senior Member funny1's Avatar
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    slower by 6 mph after the compression increase----are you running stock cams?
    I can't get my horse to wake up.

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    I do ride it back from a pass, I have 395 lift web cams, I also checked voltage from battery and its 12.17 and at coil its 11.87volts? A .20 decrease is that normal?

    I am not sure what's going on with this thing. But it shouldt have lost 4 to 5 tenths and 6mph rrom a valve job and upping the compression.. is 10 percent leakdown ok, I know its not great but it should be ok shouldn't it? Also compression test were 160

    Thanks
    Steven Davis

  7. #7
    Administrator Wade Clark's Avatar
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    Quote Originally Posted by sdavis0823 View Post
    I do ride it back from a pass, I have 395 lift web cams, I also checked voltage from battery and its 12.17 and at coil its 11.87volts? A .20 decrease is that normal?

    I am not sure what's going on with this thing. But it shouldt have lost 4 to 5 tenths and 6mph rrom a valve job and upping the compression.. is 10 percent leakdown ok, I know its not great but it should be ok shouldn't it? Also compression test were 160

    Thanks
    With those numbers the battery needs charging and if it does not go up and maintain it needs to be replaced because 12.17 is 100% discharged. Perform a load test on the battery after charging as well.

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    I charge every pass have the fbg battery and its at 12.17 with bike running, dyna said should be plenty for ignition?
    Steven Davis

  9. #9
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    To lose this much ET it is not a small problem.

    Hate to state the obvious but you just had the engine apart. The obvious is you got the cams in out of time,probably one tooth. Seen people obvious good mechanics do just this.

  10. #10
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    Ya I have had people tell me check it.. I pulled vlave cover off and am not sure how to check it.. I am trying to learn all this..can someone walk me thru how to check it in dummy terms..lol..
    Thanks
    Steven Davis

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