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Thread: Runs rough on cruise

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    Active Lancista carcrank's Avatar
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    Runs rough on cruise

    I have an S2 Coupe it accelerates and idles well but when sitting in top gear with a light throttle in the 80 - 110 KPH range it feels "woolly" or rough. I have installed an electronic ignition but it was doing it before I did that, I have checked the leads and replaced the rotor, the cap looks like new I have also replaced the plugs with Denso iridium but no change . It has been suggested the fuel pressure may be too high (I'm running a standard mechanical pump) making a bad needle and seat leak.

    I am going to do an other compression test in case a valve clearance in closing up. Any other ideas?

    Also it is definitely getting worse.

    Cheers

    Mark

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    Legendary Lancista lancialulu's Avatar
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    Re: Runs rough on cruise

    You can check valve clearances, but what fuel are you using and on a light throttle the idle circuit in the carbs is still in play and with the higher volatility of modern fuels you may need to up the idle jet size. Just a thought...

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    Active Lancista tangmonster's Avatar
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    Re: Runs rough on cruise

    my 2c

    it is always something simple.

    When last was the carb balance checked?

    No need for expensive tools to check it.

    My aquarium pipe with 2 stroke oil and nipples with o rings at the end works perfectly well.

    carb balance is much more important at lower throttle position than WOT.

  4. #4
    Active Lancista carcrank's Avatar
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    Re: Runs rough on cruise

    Yes after jumping to all sorts of complicated conclusions I think it will be something like balance or idle mixture, thanks.

  5. #5
    Experienced Lancista AB095's Avatar
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    Re: Runs rough on cruise

    I could not balance my carbs. Took it to a carb specialist & the butterflies were worn. The throttle action caused the spindle to try to move the butterflys laterally as well as open them so wearing the butterflys as well as the carb body. Body was milled round with new butterflys made up to suit. Cost a bomb but now idles beautifully even at 550 rpm.

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