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  1. #1
    need4pwr's Avatar
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    XR1800...low idle in water and shuts down.

    Hey All,
    My friend has an XR1800 with twin PV 1200 66v engines. We have a new Rebuilt engine and an original. Both are running rebuilt carbs and Dplates. 1.2 n/s, 105 pilots and 117.5 mains. Pop off is about 80. Issue was low idle would cause engines to shut down. I adjusted the idle screw to have them idle about 1400-1600rpms in the water. She ran perfect and top end on both engines is slightly over 7000. Now he went to flush the engines and both runaway. He can stop them by turning the switch off. Is the idle screw set too far in? If I turn it out, then it will stall in the water under a load.

    Any help would be appreciated.


  2. #2

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    If it is 1400-1600 in the water, it is probably over 2000 on the trailer (no resistance).

    The low speed adjuster is for idle mixture. How far are they turned out and have you worked with this to get your idle right? You may need to just open these up 1/4 to 1/2 turn, then turn the idle speed screw out to get the rpms back down. Target 1100-1200 in the water.

    There is a possiblility of you having a lean run away situation where any of your gaskets may be leaking. Possiblilities include: on the carbs or cylinder base gaskets or front or rear main seal i.e. you may be sucking in air.

  3. #3
    need4pwr's Avatar
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    Thank you Salty.

    Both engines are doing the same thing. I have not remove the tamper caps on the high or low speed screws. I'm nit sure what they are set at.

  4. #4
    need4pwr's Avatar
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  5. #5
    YudLuz2's Avatar
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    You probably have one carb on each motor not getting enough fuel. Causing the run away lean condition. It could be a needle and seat not working just right. just using a 95 gram spring to lower the pop off can help while its running on the trailer. Also check each plug, I expect one of them will look a little leaner than the other two.

  6. #6
    need4pwr's Avatar
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    Thank you. Do you think it may be a rich condition since I increased the low speed jet from 87.5 to 100? Then I compensated by adjusting the idle screw higher to keep it running? Maybe dialing in the low speed screws will work? What is the best way to remove the tamper caps?

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