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  1. #1

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    HELP - Piston tops too Clean - need ideas ?

    Hi - photo is of a 99 xpl with pro k's - lows 85 - highs 167.

    Click image for larger version. 

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    This motor has been too clean like this for two seasons. Head is the same as is exhaust manifold - performance is not really flash but will rev to near 7k. It's had maybe 2 tanks of stunning performance and then randomly goes just ok for 6 months before another spurt of brilliance.

    Thought it was a water leak steam cleaning the engine but i've stripped it so many times and resealed the manifold / exhaust gasket heaps and never seen any improvement or found a problem.

    Plus there is no wear on cylinder walls so don't think it's a water leak.

    Think it might be being fuel washed but not sure how.

    Maybe fuel return system is blocked and so fuel pump is generating too much pressure so overloading motor with gas ????
    Maybe accelerator pump system is "leaking" fuel into motor ?????

    Any other ideas ???


    Thanks,

    Phil
    Last edited by K447; 11-24-2013 at 08:03 PM.


  2. #2
    SURFnTURF's Avatar
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    You are giving up a lot of power with your carbs set up like this.This is rich and washing the piston crowns.

    I would pull the carbs off and go through them and set them up again .

    Inconsistent results usually is way too rich

  3. #3

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    i've done that a few times.

    i'm obviously doing something really wrong and keep doing it wrong.

    I think pop offs are at about 22 psi - seats are 2.5 - lows 85 - 1.5 turns out - highs 167 - quarter turn out

    I've put in another carb rebuild kit with no difference

    i'll pull the carbs but don't know what to change. Everything i know is set up where i believe it should be.

    Smaller jets ? close the low and/or high speed screws ?

  4. #4
    wkuadam07's Avatar
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    You running flame arrestors or stock breather setup? What kind of oil are you using? If it's turning 6700+ rpm the chances of it being too rich all the time are slim... what do the plugs look like?

  5. #5
    mibunkerking's Avatar
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    try a 2.3 N&S.

  6. #6
    SURFnTURF's Avatar
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    with 167.5 highs they need to be closed and 85s open at least 1.5 turns

  7. #7

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    Running pro k's with outers

    I think the oil is castrol tts. Plugs have always been ok - slightly darker than they should be perhaps but dark tan at the worst

    It's not as powerful as it should he - I'm generally disappointed with it with very occaisional good bits.
    Last edited by southernflip; 09-20-2013 at 04:43 AM.

  8. #8

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    What's 2.3 N&S ?

    So what else can i change in carbs except closing the high speed jets ?

  9. #9
    mibunkerking's Avatar
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    2.3 needle & seats. you stated you had 2.5's. stock is 2.0's. try 2.3's and set your popoff to around 20.

  10. #10

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    Ok - just pulled carbs and N&S are 2.3 not 2.5 like i thought

    Everything seems right - what can i do except close the high speed screws ?

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