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  1. #1

    2003 XLT 1200 Carb leaking!

    So I'm rebuilding the carbs on this machine with Mikuni OEM rebuild kits. I completed the first one and did a pop-off test. Readings were between 82-86 over about 8 tests. So I rebuild the middle carb and go to test and I hear leaking. The leak is coming from between the pump assembly and carb base. I pulled it apart to make sure I didn't crimp a gasket or something and everything looks fine. I put it back together and test with the same results - leaks! I've checked the pump assembly plate with a straight edge and it's fine.

    Anyone else ever have an issue like this? I'm tightening the bolts in an x pattern and to spec. I'm at a loss.


  2. #2
    mudslanger's Avatar
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    Check to make sure the O rings you replaced are the same thickness. also make sure the gasket you replaced next to the carb has the same hole pattern as the one that was on it.

  3. #3
    Quote Originally Posted by mudslanger View Post
    Check to make sure the O rings you replaced are the same thickness. also make sure the gasket you replaced next to the carb has the same hole pattern as the one that was on it.
    I will check it out but the first carb is fine...

  4. #4
    Checked new materials against old - everything looks fine. I just find it strange that the first carb was fine. I was thinking perhaps that I would change the screws to cap heads and try to put a little more torque on the bolts? I'm at a loss.

  5. #5
    Assembled the 3rd (rear) carb and it too is leaking. What is going on here?

    I'm following the instructions in the Mikuni Rebuild Kit - MK-BN44i-YAM. I've assembled as follows:
    1) fuel filter
    2) O-ring
    3) Diaphragm, Damper (clear)
    4) Diaphragm, Damper
    5) Body Assembly (the component with the check valves)
    6) O-ring
    7) Diaphragm, Pump (clear)
    Gasket, Pump

    I put the cover on and tightened to 4.5Nm as per spec in x pattern.

    To test I blocked off other inlet and return and put my pressure on the inlet.

    This carb is leaking all over the place - at the base of the carb where the assembly mates and at the cover. I tightened the screws some more and it made very little difference.

    Anyone ever have any issues like this?

  6. #6
    So from another forum I learned that apparently the issue is here that I'm pumping 80+ PSI through the fuel inlet to check the pop-off and the fuel pump is designed to work at like 5 PSI. No wonder it's leaking past the O-ring! So I guess the next question is, how do you pressure test the carb to make sure that the fuel pump assembly is in fact tight? I guess I was under the impression that when you complete the pop-off pressure test using the fuel inlet that this is also going to test the entire circuit.

  7. #7
    No leaks and I just cleaned the carbs on my 1200. Did you clean the bodies good? I brush all the aluminum gasket surfaces down with a brass brush to get them clean and smooth. You could use scotchpad too I guess.

  8. #8
    mudslanger's Avatar
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    It sounds like you have the carbs that take the thicker O rings. when these carbs are built wright they can handle that much pressure.

  9. #9
    Quote Originally Posted by kmc View Post
    No leaks and I just cleaned the carbs on my 1200. Did you clean the bodies good? I brush all the aluminum gasket surfaces down with a brass brush to get them clean and smooth. You could use scotchpad too I guess.
    All components are spotless. Are you saying that you test pop off through fuel inlet with fuel body in place and can achieve 82psi pop off without the fuel pump body leaking?

  10. #10
    Quote Originally Posted by mudslanger View Post
    It sounds like you have the carbs that take the thicker O rings. when these carbs are built wright they can handle that much pressure.
    Ok, well if you're suggesting that I didn't do it right, can you help me to get it right? Yes, these are the carbs with the o ring in the base of the carb. I'm not really sure how I could have assembled wrong but I'm certainly no expert. Any tips you can offer to correct my issue?

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