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Vaccum Leak????

Discussion in 'XJ Technical Chat' started by igormothra, Jul 7, 2008.

  1. igormothra

    igormothra New Member

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    Trying to sync the carbs but I the vacuum gauge is going ballistic any ideas???
     
    igormothra, Jul 7, 2008
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  2. Ass.Fault

    Ass.Fault Active Member

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    are you using a restrictor inline between the gauge and carb boot?
    I use a fuel filter AND a vaccum connecter with a spray straw from WD40 epoxied in tight.
     
    Ass.Fault, Jul 7, 2008
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  3. igormothra

    igormothra New Member

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    no... so what you are saying is going straight to the gauge is too much?
     
    igormothra, Jul 7, 2008
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  4. leondegrance

    leondegrance Member

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    yes... you need to use a fuel filter and spray straw to reduce the fluctuation of the vaccuum gauge..
     
    leondegrance, Jul 7, 2008
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  5. igormothra

    igormothra New Member

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    wow you learn something new everyday...... thanks guys.
     
    igormothra, Jul 7, 2008
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  6. igormothra

    igormothra New Member

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    ok.... what kind of fuel filter???? bigger the better?
     
    igormothra, Jul 7, 2008
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  7. Ass.Fault

    Ass.Fault Active Member

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    a simple riding mower is the one I use. Just anything with restriction.
    Bigger may not be best, as vaccum may be lost...but I am just guessing here.

    The straw is prob most important.
     
    Ass.Fault, Jul 7, 2008
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  8. igormothra

    igormothra New Member

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    I went out to the hardware store and picked up a quarter inch compression fitting needle valve and six inches of copper tubing and connected it between the gauge and the carb with the rubber tube. I just opened it till the valve started fluctuating and then closed it a tad. worked perfectly. total cost 6.25 I am thinking about making a manifold out of brass fittings that would allow me to do all 4 carbs at the same time. anyone already tried this????
     
    igormothra, Jul 9, 2008
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  9. RickCoMatic

    RickCoMatic Well-Known Member

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    People on here have tried everything.
    The trick is making the restrictor to reduce the full vacuum from going to the gauge.

    A simple one is a hose union with a carb cleaner red tubes epoxyed through the middle ... reducing the diameter down to the diameter of the red tube.

    Once you get the restriction going for you ... the gauge won't fluctuate so wildly.
     
    RickCoMatic, Jul 9, 2008
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  10. igormothra

    igormothra New Member

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    I got the restriction dead on, zero fluctuation now. My next question is: What should the reading be on the vacuum? at 1100 rpms I am reading between 1.5-2.0 in.Hg on every carb, but I still have the cracking and popping at 6000
    is there a set # it should be at? My shop manual isn't very clear on that and I also cut out the factory air box and installed cone filters on each carb, so I know that is going to change where that reading is going to be.
     
    igormothra, Jul 9, 2008
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  11. RickCoMatic

    RickCoMatic Well-Known Member

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    You set the Vacuum values to match the Vacuum of the Number-3 Carb.

    Sync 1 to 2
    By adjusting the sync screw of the No.-1 Carb
    Sync 4 to 3
    By adjusting the sync screw of the No.-4 Carb
    Sync 2 to 3
    By adjusting the sync screw of the No.-2 Carb.

    Now that you have them all nice and synced you are going to have to overcome cutting-out your airbox and installing Pods on that 900.

    I have one of the few remaining 900's made for the US Market in 1983
    They tell me only 1000 were made.

    If I thought there was any way I could improve on the performance of this bike by adding Pod Filters I would have done Pods too.
    But, Pods are nothing but a big, long tuning headache.
     
    RickCoMatic, Jul 9, 2008
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  12. igormothra

    igormothra New Member

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    ok that makes sense....since (like someone said in another thread) the popping at higher rpms is more a symptom of running lean...gonna have to try that.
     
    igormothra, Jul 9, 2008
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